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Everything posted by fastfordrc

  1. The Fokker Dr.1 only has one set of ailerons, on the upper wing: It was the Sopwith Triplane that had ailerons on all 3 wings. As the Dr.1 only has one of the wings 'active', you could use the conventional RC aileron control method of either 1 centrally-mounted servo with control rods running through the wing ribs to 90-degree bellcranks to operate the ailerons, or 2 slim 'wing' servos fitted in the wings to operate each aileron directly. You should only need a 4-channel radio (throttle, elevator, rudder, ailerons), or possibly 5 if you want a switch channel to operate a sound/light unit for the guns. You will definitely need rudder control - rudder and elevator are the 2 most basic controls for flight (they were the only controls on the first RC planes). Even if you use aileron banking to turn the aircraft, you have to apply rudder at the same time to stop the plane losing height in the turn. Rudder is also essential to keep the plane running straight on takeoff and landing. NiCads aren't really used as a power source for electric planes these days - they usually use LiPo packs and brushless motors due to the lighter weight (LiPo has a higher energy capacity for a given weight compared ot NiCd/NiMh) and more efficient power delivery. A BEC (battery eliminator circuit) steps down and regulates the voltage from the drive battery to a constant 5 or 6V so you can power the receiver and servos from the main drive battery You can either get a standalone BEC, or some aircraft ESCs have them built in (as they are with most car ESCs). Some aircraft modellers are still a bit suspicious of using BECs in planes and prefer the added safety a keeping a separate receiver pack - if the drive battery 'dumps' in flight and you lose power to the engine, you would still have power to the receiver and servos to make a controlled glide to land. The other important thing to consider when flying model aircraft is insurance - a 1/10th scale wooden aircraft with a powerful brushless motor swinging a big prop can cause serious damage to property or injury to people in the event of a crash. It you aren't already a member and don't fancy organising you own third-part public liability insurance, it's highly recommended that you join the British Model Flying Assocation (usually via joining an affiliated flying club), and you would then be covered under their insurance scheme: http://www.bmfa.org/.../insurance.html
  2. The same radio (Core RC is a brand owned by Schumacher) is also sold in the UK branded as the Tamco TAC330 (distributed by Amerang) and Etronix Pulse EX3GPro (distributed by CML). The Etronix version is available in both a stick and pistol-grip versions, and the pistol-grip version is also sold as the HobbyKing HK310/GM Racing (Graupner) XG6i/Robitronic TL-3C/Venom V3RT/Modelcraft (Conrad) MC30. The case of the pistol-grip version looks to have been 'inspired' by the Sanwa MX3. The OEM manufacturer for the radio is Xinyi/HiSKY (Guangzhou Chiyuan Electronic Co., Ltd, China) http://www.tradeeasy...2/selling-leads http://www.chiyuan.n...llClass=&page=1 The pistol-grip version is the CY-310. The stick version (CY-330) uses the same innards but built into the case of the CY-200 model, presumably created for markets where stick radios are still popular (such as the UK). The OEM version of the receiver is the XY3000 - some of the rebrands have kept this number (Robitronic), or modified it slightly (Hobbyking HK3000). The original version of the pistol-grip radio also appears unbranded as the 'N4-Q'. There are 3 versions of this model - the original 40MHz FM model, a 2.4GHz DSSS (non-frequency-hopping) version, and the current 2.4GHz FHSS (frequency hopping) version, The stick version appears unbranded as the 'N3-S'. some the rebranded models (Etronix, for example) were originally the DSSS versions and were later replaced by the FHSS versions (but with the same model number!). The DSSS and FHSS TXes and RXes are unfortunately mutually incompatible. The lower-spec pistol TX models (CY-220 and CY-300) and the receivers are also found in a lot of RTR car sets branded as the manufacturer's own products (OFNA/Hobao and Great Vigor, for example). I have also seen this lower-spec TX sold on it's own packaged with a XY3000 receiver as the Intech/Power Racing/Etronix CY300 If you find any 2.4GHz 3-channel receivers from the above brands they will probably work with the Code radio as well. If it's one of the unbranded 2.4GHz receivers to make sure it's the FHSS version.
  3. It's possible that the blue/purple wire might be a 'centre tap' from the battery pack, to provide 4.8 or 6V to the receiver PCB (i.e. a cheap way to avoid having to include a BEC circuit). The only way to find out for sure is to put a voltmeter between the black and blue wires and black and red wires.
  4. As I explained above, as it's been built around a 2.4GHz RF module it can only use PPM modulation, which limits it to 8 channels. The large piece of heatshrink on the antenna is a cover - unlike your Futaba antennas which are just coax cable with the 1/4 wave section of the centre core exposed at the end as the antenna, the 'lump' at the end of the Turnigy antenna is a 'sleeved dipole'. The coax will be threaded through a plastic sleeve, with the 1/4 wave centre core going straight through it and the outer braid (or a wire connected to it) bent back over the side of the tube. The heatshrink over the top is to keep it all in place. The effect is to try and get better reception sensitivity from a single coax antenna. This is Flysky/Turnigy's solution at trying to give their receiver some kind of antenna diversity without totally redesigning it. The very early V1 FlySky systems only had a single antenna (as is seen on most 2.4GHz surface and short-range 'park flyer' receivers), and had reception problems when used in aircraft as a result (on top of the interference problems the V1 system had due to not having frequency hopping). Most other 2.4GHz aircraft receivers have radio sections designed to use 2 antennas to give better reception at whatever orientation the receiver is to the transmitter (this is known as antenna diversity). To combat this problem quickly, Flysky simply added a second radio section into the same case (known as a 'satellite' receiver) .See the pic below - the V1 receiver is on the left with the tacked-on satellite PCB, and the V2 is on the right: The V2 FlySky receiver's digital section design has been modified to implement frequency hopping, but the radio section designed around a single antenna has been retained. However, to reduce costs they have removed the satellite radio section, and added the screened dipole antenna as a cheaper alternative solution.
  5. It was very successful. Delta had been one of the big names in 1/8th onroad racing since the late 1960s, and Art Carbonell was their star driver, wining numerous championships. Towards the end of the 70s 1/12th onroad was becoming more popular, so Delta started looking at producting a car to compete in that class (their first design, the Phaser, was an upgrade kit for the then-dominant Associated RC12E). Delta signed up Kevin Orton to assist in this effort (he already had a reputation for innovative ideas in the 1/12th racng scene). Kevin's first big improvement was introducing the t-bar and oil damper suspension system for the rear motor pod on the Super Phaser: This then went on to be universally adopted by everyone else, and is still the template for current pan car designs. Art Carbonell won the 1982 1/12th Modified World Championship with the Super Phaser, but he was still using a resistor-based speed controller at the time (the one to have then was called the 'Work-Rite', which used a bank of 8 resistors). Kevin came up with a clever modification for the throttle stick on the team's radios - a switch that moved the servo arm just past the upper limit of it's throw. This was turned on before putting the car on the grid and the stick was pushed full forward. When the race started the switch was turned off and you got instant full throttle off the line without having to wait for the servo to move it's full throw (similar to what a lot of full-size sports cars can do now with full-throttle starts), When the AutoDrive ESC was introduced though, the MSC became obsolete in racing. Orton also developed the technique of matching cells to build packs - before this racers usually brought a crate of packs to each event, using a new pack for each race. The Delta factory drivers with their matched cell packs would only bring 3 packs for an entire event. The other major development Orton came up with was peak detection charging, with Delta producing the first commercially-available chargers (hence why they became known as 'Delta Peak' - the name is a 'Hoover/Vacuum Cleaner' situation). Unfortunately, as seems to be the case with a lot of technically brilliant people, he was not a brilliant businessman. By all accounts he did not have very good interpersonal skills.either (which is one of the reasons Delta were happy for him to leave and set up Tekin) and it became apparent to his employees he had mental issues. He invested his money into property which did very well for him, so when running the company became too much (he ended up refusing to answer phone calls or orders from distributors) he wound it up and disappeared from the RC world. He has no connection to the current Team Tekin company.
  6. They seem to be OK, though at that price there will be an element of 'you get what you pay for'. A lot of people have commented on the variable build quality (Turnigy seem to be very keen on hot glue). They use the FlySky V2 FHSS 2.4GHz TX and RX modules, which although better than the original FlySky V1 system (which did not frequency-hop, and had some serious problems as a result), still has some drawbacks - the receivers have no built-in failsafes, and only have a single antenna so there is no antenna diversity. It's for these reasons that a lot of aircraft modellers have upgraded their 9Xs with FrSky DIY modules and receivers. Turnigy have made this more difficult in the V2 version of the transmitter though, as the TX module that clips in the back can't be fully removed - the antenna is hard-wired though to it via holes in the rear case and PCB, so it either has to be cut or desoldered off the TX module PCB to allow it to be removed. If you aren't going to use it for aircraft or nitro cars then these issues aren't really a problem - I went with the FrSky module to mod my MC10 as I wanted the failsafe for my 1/8th scale tank (I didn't want something weighing 70kgs going out of control). If you want to use it on Tamiya trucks with an MFU then having digital trims instead of analogue ones will make things awkward (though I see that some of the open firmware hacks have a mod to make the throttle trim buttons work like a slider - you would need to apply this to all of the trims). The only other thing is it's intended to be an aircraft radio, so the Y-axis on one of the sticks will be on a ratchet to be the throttle. If you want both sticks to centre in both axes, you will need to get the parts (coil spring and centring lever) from another 9X, or a radio that uses the same stick units. The '9 channel' thing is a bit of a misnomer as well - the 9X V2 can only ever use 8 channels as that's all the PPM signal through to the 2.4GHz TX module can carry. The V1 version of the transmitter had a fully removable TX module (the 2.4GHz antenna was on the back of the module). The radio had a telescopic antenna on the top of the case for use by 72 or 35MHz TX modules. When one of these modules was fitted, the radio could be switched from PPM to PCM encoding, and that is how the extra channel could be used (you needed their specific PCM receivers to decode the signal though). Unfortunately this facility was removed from the V2 version, as the 2.4Ghz module can't be fully removed, and the telescopic antenna was deleted in place of the fixed 2.4GHz one.
  7. The first ESCs for use in RC cars were made by Don McKay of Jerobee/JoMac in the mid-seventies, forming part of their 'Brick' integrated receiver/servo/ESC module. You can see the heatsink at the rear on this old ad picture: Also see this link where someone has gutted an original unit to fit modern gear into a on old Jerobee car: http://www.rc10talk....hp?f=33&t=29015 The JoMac design was relatively simple though, and although people started developing the idea a lot of drivers continued using MSCs, which were also still being developed (with braking resistors being added and so on). The first solid-state MOSFET-based ESC as we know them today (the Delta AutoDrive) was developed by Kevin Orton in 1981 while he was a driver for the Delta factory 1/12th onroad team (he then went on to form Tekin): The Mk1 version is on the left here, with the Mk2 on the right: Between the JoMac and AutoDrive speed controllers there were other designs around in the late 70s/early 80s for 1/12th onroad that were either simpler transistor designs or electro-mechanical (a mixture of transistors and relays used to switch between multiple speed steps - the Hilux E-MSC was similar to this except it used a servo to switch between the steps). It was around the early 80s when they first started appearing in 1/10th offroad (once it was possible to make them at least semi-waterproof). Acoms even made the AP35 specifically for the SRBs ( http://www.studio68....ult.asp?id=6400 ) though that was still an electro-mechanical design.
  8. Not quite - you will have to bind/link the new receiver with your transmitter (if you bought a transmitter-receiver combo for your first truck they come already linked together from the factory). It looks like the procedure for the 6EX is turn the transmitter on, then turn the receiver on and press the 'Set ID' button for 1 second. The receiver's LED should turn green when it's linked to the transmitter (it's on page 9 of the manual).
  9. The BEC (Battery Eliminator Circuit) was originally introduced to power the receiver and servos from the main battery pack, removing the need to use a separate 6V receiver pack on electric models. The packs were either 7.2 or 8.4V which was too high for the receivers and servos, so the BEC is a voltage regulator circuit that takes the input voltage from the battery pack and outputs a regulated 5 or 6V (though now they are available up to 12V to power high-torque servos). BECs originally started off as separate module you plugged into the receiver battery socket (The Hotshot came with one in the kit, as it had no space for a receiver pack), then started being built into receivers and ESCs. Nowadays with LiPo packs available in higher voltages, servos being available that can take more than 6V or need a high-current supply and micro receivers with no onboard BEC, external BEC modules have made a comeback. Electrically, there should be no reason why you couldn't use 2 BECs together in parallel - for instance, say the ESC's BEC could deliver 3A at 5V, and you plugged in an external BEC that had the same rating then theoretically you would have the ability to supply 6A at 5V. However, in real life this would only work if both the BEC circuits were of the same design and the same type. There are 2 methods to deliver a regulated voltage - a linear regulator circuit (mostly found in receivers) and a switched-mode regulator circuit (which is used in most ESCs). External BECs can be of either type. You can only use linear regulators in parallel, and then only if they have the same output voltage. Trying to use a linear and switched-mode or 2 switched-mode regulators in parallel is not a good idea at all, and it what BMT is referring to when he says about harmonics interfering with each other (which is what you get with 2 switched-mode regulators). They interfere with each other's load-detection circuitry which can cause them to go into overload, get hot and either be damaged or go into thermal shutdown (if they have been designed properly) BMT's advice about isolating the positive supply pin in the ESC's lead to the receiver is correct, and usually appears in ESC manuals to cover installs where they will be used with an external BEC.
  10. Just a bit more info for if you get a 4-channel stick radio for a truck or 3-speed and find the throttle axis of the left stick is on a ratchet instead of a self-centering spring (this is what my Techniplus 4 was set up as, even though it was meant for use with 3-speeds). That is the throttle setup that is commonly used on 4-channel aircraft radios (known as 'Mode 2' - 'Mode 1' is where the ratchet throttle is on the right stick), but it's not ideal for use with a 3-speed. Open up the back of the radio and look at the back of the left stick mechanism. The Y-axis (throttle) will have a flat metal spring screwed on that presses against a toothed surface on the back of the stick to provide the ratchet. The X-axis (gears) will have a plastic lever that presses against a cam on the stick axle, held against it by a small coil spring. This lever is what pulls the stick back to the centre. For a 3-speed, you want the throttle axis to self-centre, but it's not a problem having the gear axis on the ratchet (it stays in whatever gear position it's in when the throttle goes back to neutral). To do this, you just need to carefully unscrew and remove the ratchet spring, unhook the coil spring and lever from the X-axis and refit it on the Y-axis (tweezers or needle-nose pliers are usually required), and then screw the ratchet spring onto the X-axis. Of course, if you want to have it self-centering on both axes, you can move the ratchet spring over to the Y-axis of the right stick instead (which is the same as converting from 'Mode 2' to 'Mode 1' on an aircraft transmitter).
  11. <p><p> The one in the first link is a 72MHz aircraft radio, which you shouldn't be using in a surface vehicle unless you convert it to 2.4GHz using a DIY Module. The one in the second link is a 75MHz set, which is the surface frequency in the USA so that should be OK for you. As it seems you are in the US, I've also found this: http://www.ebay.com/...=item19d6e3290 from the same seller as the second radio. These are also these, which is the type of cheap 2.4GHz systems I was talking about - still analogue sticks and trims, but with a 2.4GHz RF section: http://www.ebay.com/...=item20b2c6341f It's still a 4 channel radio with analogue trims, it just has a 2.4GHz RF transmitter insteas of an old AM or FM one. Also, here is a link for a nice alloy shift gate to go on the throttle stick: http://www.ebay.com/...=item5897bfcba7
  12. I have recently added a new model to my showroom and made some typos in the description text. I click on 'edit model' and get the editor, correct the mistakes and then click on the 'update' button, but the changes to the text don't appear. Does it take some time before the updates appear? I'm on Win 7 and have tried it on IE8 and Firefox 16.0.2
  13. Well, my package has arrived from GiantShark, so it's time to stop waffling on about theory and actually do a conversion. The contents of the FrSky V8HT DIY Module package looks like this: There are 3 sets of leads coming out of the module - the aerial coax cable (with the gold-plated fitting on the end), the Bind button/Status LED lead (with the small PCB on the end) and the power and PPM input. This is the important one, and of you look closely one of the 3 wires in this lead has a heat-shrinked section at the end. This is the PPM input, and the heatshrink is covering a zener diode which has been soldered onto the end of the lead. This was an important modification suggested by the users on the RCGroups and GiantShark forums that protects the module's circuitry from being damaged by the PPM output generated by certain designs of transmitters. To install the module, you need to find somewhere to put the module, aerial, Bind/Status PCB and then solder up the 3 connections. The transmitter I chose was the Techniplus MkV, as it's my favourite one to use, and in my opinion probably the nicest-looking of the Acoms units I have. Firstly i looked for a location for the module. In my previous post about the MkV I said there wasn't much room in the case, and I found this to be true. A few temporary fittings using sticky tape showed that the best place to fit it where it didn't interfere with the stick mechanisms and gave easy cable routing was on the far right of the rear case, snugged up against the top of the battery compartment: Notice the heatshrink on the yellow wire - I have moved the zener diode further up the PPM input wire. I needed the connections to the PCB to be flexible, which wouldn't have been the case with the diode at the end. Next, I looked for a position for the aerial. As I wasn't keeping the 27MHz RF section functional, I decided to use the existing position, but this meant the case needed modification. The aerial support boss on top of the case is moulded as part of the front half of the case, but there is a thin section under the base which is split in half between the front and back of the case. I cut the boss off flush with the top of the case, then added a half-ring of ABS underneath to reinforce it and give a level surface for the aerial fitting to be bolted up to (this required the thin section on the rear half of the case cutting away to fit as well): The next thing was to find a position for the bind/status PCB. Some people mount these on the back of the transmitter case, but I wanted the LED somewhere where it was visible in use. As I wasn't keeping the 27MHz RF section functional, that meant the hole for the crystal socket was available. Again, a few trial fittings showed that this needed a bit of modifying. If the bind PCB was sandwiched between the hole and the radio PCB, it meant the radio PCB sat about 2mm too high and the case wouldn't fit back together, and the hole was too deep to use the bind button. I ended up cutting 2mm off the back of the hole for the crystal, which meant the bind button would end up flush with the front: The reinforcing webs were also trimmed to make room for the cable and to let the PCB sit squarely. The original PCB now fitted back in place, but when the button was pressed the bind/status PCB would push inwards as well. The solution to this was to put a blob of hot glue on the back of the PCB. One it cooled, it meant the crystal socket on the original PCB was pressing against the back of the bind/status PCB, holding it firmly in place: The 4-way cable fits through the gap between the original PCB and the bottom on the case, then folds upwards and runs in the gap between the solder side of the PCB and the battery box in the rear half of the case. it can be seen at the top of this picture: The power and PPM input cable can be seen above, running diagonally down to the PCB. This also folds at the bottom when the case is reassembled, which is why I didn't want to leave the zener diode at the end. The connections and cut tracks can be seen in more detail below: The black wire is the Ground, which was soldered to a convenient pad on the ground plane. The red wire is the power supply, and is soldered to the track that supplied power to the existing RF section. The yellow wire is the PPM input, which is soldered to the output of transistor Q4, as identified in my previous post. The 2 cuts isolate power from the existing RF section. In my original post on this radio I suggested 1 cut, and disconnecting one of the legs of inductor L4. The upper cut in the picture above does the same job as lifting the leg of L4, as I was not keeping the original RF section switchable. The aerial connector was then bolted in place and the 2 halves of the case were carefully put back together, taking care not to snag any of the new wiring. The transmitter was then powered up, and the flickering LED indicated that a valid PPM signal was being received by the module. I then connected up the 4-channel receiver to a battery pack and servo, and went through the bind procedure (very simple - power on the TX with the 'bind' button pressed, them power on the RX with the 'bind' button pressed, though you have to be careful not to have them too close together while doing so). Everything is now working OK: I have another TX module to use, which is for my Graupner MC10. That should be easier, as it has a trainer port connection on the PCB so the power and PPM signals are easily accessible.
  14. The Acoms AP401 Techniplus 4 is also suitable (if you can find one as it has been discontinued for a while too). If you are in Europe, look out for the Conrad Razor X4 - it's the same radio rebadged by Conrad. There are also lots of cheap new 2.4GHz twin-stick 4 channel radios with analogue trims around on ebay too thanks ot the foamie/park flyer market (I have just found 2 TX/RX sets on the first search page that were under £40). If you are really struggling to find one, another idea might be to get an old AM/FM 4 (or more) channel twin stick transmitter and convert it to 2.4GHz using a 'DIY' module. As it's going to be running 2.4GHz, it doesn't even need to be a surface radio to start with, and there are lots of cheap old 35MHz (or 72MHz in the USA) aircraft transmitters available that are suitable subjects for conversion.
  15. You should be ok with that supply. The charger is rated at 140Watts, so if you connect it to that power supply set to 12 Volts and then apply Ohm's Law (Amps = Power/Volts), then 140W divided by 12V gives a current of 11.67 Amps. The power supply has an adjustable current limit of 0 and 15A so it should have no trouble delivering 12A at 12V (the power supply is rated at 200W, which means the maximum current it can deliver at 12V is 16.67A). You just have to remember that if you set the power supply to 12 volts, you will also need to set it's current limiter to 12 Amps to work with the charger.
  16. Before I go on with any more radio details, I thought it might be a good idea to discuss some of the various 2.4GHz DIY modules that are available. Jeti (from the Czech Republic) and Xtreme Power Systems (XPS) were amongst the first manufacturers to offer a 'DIY' 2.4GHz upgrade module that could be used on any transmitter (Jeti even designed installation kits for various popular transmitters). XPS got a lot of bad publicity early on as the 'frequency hopping' algorithm of their system did not work very well with interference and the receivers would lock up (a big problem, as aircraft modellers were their target market). Both systems were very expensive, which was to be expected in the early days of the technology (but they could also could work with the most complex high-end transmitters, such as those that used faster scanning and longer PPM frames to allow up to 16 channels to be used). Once radio manufacturers started bringing out plug-in 2.4GHz RF modules for their transmitters (and some started offering them for other manufacturer's transmitters), people started looking at them as a cheaper way of modifying existing radios that either didn't have module sockets or did not have a 2.4GHz option available. Once this started becoming a worthwhile market, various far-eastern manufacturers started making their own 2.4GHz systems, As of now, there are numerous manufacturers in the 'DIY Module' area, such as Assan, Corona, Flysky, FrSky, Flydream and WFly. When it came to choosing which system I wanted to go for, I read a lot of reviews and opinions of people on forums. Originally I was going to go with the Corona V2 system, but in the end I settled on the FrSky system. My main reasons for choosing FrSky were 1) They are fully CE and FCC approved. 2) They have a UK distributor (GiantShark) and are readily-available. 3) They have implemented a full-featured frequency hopping algorithm with a fast 'lost signal' recovery time and their receivers have a proper failsafe function that can be programmed for each channel. 4) There is a wide user base for surface models (a lot of the members on Oople have converted their old high-end car radios with FrSky modules and 4-channel receivers) 5) FrSky maintain a technical presence on forums like RCGroups and Giantshark's user forums and seem to be very receptive to customer suggestions 6) Although they are not the cheapest, they are still competitively priced (currently £13 for the non-telemetry TX module, and £13 for the 4-channel receiver) 7) The PPM input of the module is tolerant of a wide range of input voltages (I have tested it with PPM 'high' pulse levels of 0.6V up to 12V) and will accept both positive and negative-pulsing PPM signals. Some other modules will only accept positive-pulsing PPM signals of at least logic-level (3.3V), and so require additional circuitry to invert negative-pulsing PPM signals or boost lower-voltage PPM signals. The transmitter module I ended up purchasing was the V8HT DIY module (this is the non-telemetry version) and a couple of receivers - the V8R4-II 4 channel unit, and the V8R7-II. These 'Version II' receivers are compatible with both the non-telemetry and telemetry versions of the TX modules, but do not send telemetry back (the 'D'-series receivers are the ones with telemetry capability). This could be important if you intend to use it for racing, as telemetry may be against the rules (it is for BRCA-sanctioned events in the UK), and the presence of a telemetry-capable receiver may cause trouble with the scruitineers. One other thing to remember about 2.4GHz systems is that unlike 27MHz and 40MHz systems, by and large no two manufacturer's products are compatible with each other, though there are a a couple of exceptions. Some JR and Spektrum receivers and transmitters will work with each other (not surprising, as JR make both) and there are now some third-party JR/Spektrum and Futaba compatible receivers on the market. For all other systems, you have to buy transmitters and receivers from the same manufacturer. The reason for this is because each manfacturer has developed proprietary spread-spectrum implementations and frequency-hopping algorithms, and don't want to give this information away to their competitors. However, if the user base is large enough (as is the case for Spektrum and Futaba) then the other companies will find it worth the effort to reverse engineer the big name's systems, so they can get a slice of their receiver market. Another important thing to remember is that hardly any 2.4GHz receivers have BEC circuitry built into them. Some manufacturers make receivers that will work with supply voltages up to 13V (these are usually marked 'HV', or something similar), but the regular receivers will only take a supply voltage of 4.8V-6V. You either need an ESC that has a built-in BEC or an external BEC module between the ESC and receiver, even for 'HV' receivers (otherwise they would end up supplying up to 13V out to the servos, which wouldn't be very good for them).
  17. Thanks for the comment. RX antenna wire lengths is a bit of a minefield. Antenna theory would have it that for best reception, an antenna length based on a fraction of the wavelength (1/2, 1/4 or 1/8) would give best results, with quarter-wave being the optimum. However, for 27MHz a quarter-wave antenna would be approximately 2.8 metres long, and for 40Mhz it would be 1.9 metres long (as the frequency increases, the wavelength decreases). These antennas would be too long for fransmitters, never mind receivers (though a transmitter could get away with an eighth-wave antenna at half those lengths with reduced performance). However, to get around the need for a long antenna you can design the transmitter and receiver circuits to have an 'impedance matching' circuit in line with the antenna. This allows you to tune the circuit to give good perfomance with a much shorter antenna (especially important for receivers). The ideal antenna length for the tuned circuit is decided at the design stage by the manufacturer, but from a quick survey of my 27MHz receivers it seems around 50cm seems to be a common length (the only 40MHz gear I have is JR Graupner, and they seem to tune their receivers to use much longer antennas). If your antenna gets damaged, it's probably safest to either get a replacement wire from the manufacturer/distributor (they are usually available as spare parts) or find someone with the same model and ask them to measure theirs so you can replicate it (I usually measure the antenna of any new type of RX I get before it's installed and make a note of it in the manual, just in case). If you have no idea, and having the optimum range or signal to noise ratio isn't too critical, then 50cm would seem to be as good a guess as any for a 27MHz receiver antenna. Out of interest, this page is a good practical study of changing the length of the antenna wire and the effect it has on signal strength: http://www.rc-cam.com/ant_exp.htm The antennas for 2.4GHz systems are much more sensitive to length changes. as the higher frequencies mean the antennas will be much shorter and so exact length becomes more critical. A quarter-wave antenna for 2.4GHz comes out as about 3.2cm, which is about the same length as the little stub of wire you get on most 2.4GHz surface or park flyer receivers. Multi-channel 2.4GHz receivers designed for large aircraft and helicopters usualy come with 2 antennas, made from short lengths of coax with a length of bare wire at the end. The 2 antennas form a dipole, which provides better directional reception as the model moves in 3 dimensions relative to the transmitter (this is known as 'antenna diversity'). The length of bare wire at the end of the coax is actually the antenna, which again is usually about 3.2cm long.
  18. While I'm looking at the connection between Acoms and JR, I thought I'd document the Graupner C4-X next, which is a rebadged version of the JR Propo Beat Gear. It dates from around the same era as the AP27 MkV Techniplus, and once you open the case you find that they have a lot of things in common - the same stick mechanisms, and the PCBs are virtually identical, with just some minor component position changes. The PCB is numbered '1771-503-0-91', which fits into the same numbering scheme as the other JR/Acoms designs (the Techniplus MkV is '1771-500'). However, instead of the mechanical voltmeter, it has a simple 3-LED meter. Again, any advice below is provided for educational purposes only. Here's a picture of the PCB: Compare it with the MkV PCB earlier in the thread - it's virtually identical. Just as in the MkV, the PPM output appears on the emitter of transistor Q4 (the component names are the same on both PCBs), and can be picked up at the solder points on the pad outlined in blue. As wih the MkV, the PPM signal is active high, and pulses up to Vcc (12V). The ground connection for the module can be picked up from anywhere on the ground plane, or from the negative battery terminal. To get power for the module, I would suggest soldering direct to the switched power - the top pair of contacts on the switch, or the large square solder point just under the aerial bracket that the pinkish-red wire from the switch is connected to. Just like the MkV, there are 2 separate power feeds to the RF section. To disable the feed to the crystal ocsillator, I would suggest cutting the track at the yellow line on the Vcc track. To disable the power for the RF amplifier, heat the solder on the right-hand pad of inductor L5 (the side connected to Vcc) and use tweezers or pliers to lift the leg from the hole. If you wish to switch between 27MHz and 2.4GHz, use a SPDT switch. The centre connection would be connected to one of the solder points on the 'Vcc' pad in the picture above.. One of the outer connections would be back to the PCB (one of the 2 solder points on the other side of the cut) to power the crystal oscillator, and to the lifted leg of L5 to power the RF amplifier. The other connection on the switch would be the power line for the 2.4GHz module. Although the case is a bit chunkier than the MkV's, there is only the same amount of room inside (the extra depth is due to a thicker bezel around the sticks). If you want to keep the 27Mhz output usable, the only space I can see is to the upper left of the steering stick. If you just want to convert to 2.4GHz, the space between the sticks where the aerial was becomes available.
  19. After a bit more research, it turns out there is a relationship between JR and Acoms/Asahi Corp/Casio Creative Products. JR's lower-end radios are built in Asahi's factories in Malaysia and Thailand. It looks like as part of this deal Asahi were allowed to rebox/rebadge these JR designs and sell them under their Acoms brand (which would explain the similarities in the circuit designs and 'JR' markings appearing on the PCBs of the later models). My guess is that that Asahi were only allowed to export the Acoms-branded JR designs to countries where the JR importer does not take the lower-end gear. This would explain Acoms' ubiquity in the UK market, as MacGregor (JR's UK importer) only deal in the higher-end JR sets. Germany is an interesting situation, as Graupner import and rebadge JR gear (including the low-end 'Beat' 2-channel sets, which are rebadged as Graupner C4/C4X), and Carson import Acoms gear, so you end up with the same designs being sold by 2 competing companies. Horizon are JR's partner for US market (JR also design and build the Spektrum sets for them too), and also they import the lower-end pistol-grip JR sets (and rebadge some of the JR-designed Acoms gear under thier own brands). It looks like this restricts Acoms from having much of a presence in the US. I wonder how the relationship works now, after Casio sold Asahi Corp/CCP to Bandai in 2006?
  20. Last of my Acoms 2-channel sets is the AP202 Techniplus. Back to an all-transistor design, but now most of the components have been changed for surface-mount equivalents (except for the larger capacitors and inductors) which are mounted on the solder side of the PCB. The PCB is marked '3511-500-1-91' on the component side, which would suggest it was the next PCB to be designed after the AP201. Another interesting detail is the PCB is also marked 'JR CH7D'. This would indicate it is actually a design licenced or made by JR, like the AP401 Techniplus 4 and the Technisport Hayabusa (which was a rebadged JR Cobra). A bit more research shows that this exact model was also sold as the JR Propo Beat Sonic in Japan (http://www.jrpropo.c...69&db_flg=jp_dl), which was the replacement for the Beat Gear at the bottom of the JR range. It also makes me wonder if the Casio takeover had reduced Asahi/Acoms to an offshore manufacturing and rebadging/reboxing company with no design input. Like the AP201, there is a small daughter board for the LED meter. However, in this design it is just the for the meter, the switch and power control circuitry are now back on the main PCB. As usual, any advice below is provided for educational purposes only. A picture of the solder side of the PCB: Although the change to surface-mount components makes it look very different, the circuit is very similar to the AP27 MkV (though it in now a bit more tricky to modify). The PPM output appears on the emitter of the transistor outlined in blue (there are no component names now), and can be picked up at the solder points on the pad outlined in yellow. This pad is now quite small, so rather than soldering to one of the tiny SMD solder pads I'd suggest carefully scraping the lacquer off in the middle of the pad to get to the copper, and soldering to that. As wih the AP27 MkV, the PPM signal is active high and pulses up to Vcc (12V), The ground connection for the module can be picked up from anywhere around the large ground plane (or from the solder point marked 'BK' that has the black wire attached). To get power for the module, I would suggest soldering direct to the switched power - either the leftmost rectangular pad for the switch, or the solder pad further up the track where the red wire is attached. As in the previous transistor circuits, there are 2 separate power feeds to the RF section. To disable the feed to the crystal oscillator, I would suggest carefully removing the zero-ohm resistor (outlined in red, and marked with the value '000' - zero-ohm resistors are used in surface-mount circuits as equivalents of a wire jumper connection). To disable the power for the RF amplifier, carefully unsolder the leg of inductor L4 from the pad where it connects to the switched power track. This disables the RF section permanently. If you wish to switch between 27MHz and 2.4GHz, use a SPDT switch. The centre connection would be connected to one of the solder points on the 'Vcc' pad in the picture. One of the outer connections would be back to the PCB to the tiny solder pad on the 'crystal' side of the removed zero-ohm resistor to power the crystal oscillator. and to the lifted leg of L4 to power the RF amplifier. The other connection on the switch would be the power line for the 2.4GHz module. There is a bit more room inside this case, as it's a bit deeper. There should be just enough room to fit a DIY module in the centre of the rear half of the case behing the existing aerial if you want to keep the 27MHz RF section functional.
  21. Now onto the AP201 Techniplus Alpha. This transmitter is built around the Oki L9362 'Encoder on a chip', and is totally different to any of the other Acoms designs (which makes me wonder if they either copied or licenced a circuit design from Futaba or JR). It runs on the now standard 8AAs, meaning Vcc will be around 12V. Another difference in this design is that it uses 2 PCBs. The main encoder/transmitter board and a daughter board that contains the LED voltmeter and power switch. The battery and charge port connections are carried from the main PCB to the daughter board via a 4-way ribbon cable, with the Vcc supply for the main board being returned through one of the wires in the ribbon cable. As usual, any advice below is provided for educational purposes only. Here's a picture of inside the radio, the right-hand side of the solder side of the PCB: Now, this is very different from the previous two PCBs, and is a lot easier to convert. The L9362 chip handles the encoding - it is a 14-pin device, and the PPM signal is output on pin 9. This can be picked up on the small PCB pad outlined in blue connected to that pin. Power to the RF section is taken from the Vcc track (the inverted 'T' shaped track coming from the ribbon cable connection) via a wire jumper, J2, on the component side of the PCB. Disconnecting this jumper should be enough to leave the RF section unpowered. If you wish to switch between 27MHz and 2.4GHz, you could wire the two pads at the ends of jumper J2 to a switch, which could then be used to switch Vcc between the 27MHz and 2.4GHz RF sections. Again, there is not a lot of spare room inside the case - it uses the same deep stick mechanisms as the AP27 MkV, so pretty much the only place to mount a DIY module would be in the space between the sticks occupied by the existing aerial.
  22. Next in chronological order, it's the AP27 MkV Techniplus. This design has moved on to using 8 AAs, meaning the supply voltage (Vcc) will be around 10-12V, depending on the batteries. My example is fitted with a PCB that is marked '1771-500' in the ground plane copper on the right-hand edge of the solder side, and also sikscreened on the component side above the crystal socket. Again, any advice below is provided for educational purposes only. Here's a picture of inside the radio, the left-hand side of the solder side of the PCB: Again, the PPM output appears on the emitter of transistor Q4 (the circuit is so similar to the Mk2 that most of the component names are the same), and can be picked up at the solder points on the pad outlined in blue. As wih the Mk2, the PPM signal is active high, and pulses up to Vcc (12V in this case), again check this is suitable for the module you choose. The ground connection for the module can be picked up from anywhere around the large ground plane that occupies all the unused space arond the board (or from the negative battery terminal). To get power for the module, I would suggest soldering direct to the switched power - the top pair of contacts on the switch, or the square pad on the PCB that the red wire from the switch is connected to just below the aerial bracket (hidden under the brown/yellow pair of wires in this picture). As in the Mk2, there are 2 separate power feeds to the RF section. To disable the feed to the crystal ocsillator, I would suggest cutting the track at the yellow line on the Vcc track. To disable the power for the RF amplifier, heat the solder on the right-hand pad of inductor L5 (the side connected to Vcc) and use tweezers or pliers to lift the leg from the hole. This would disable the RF section permanently. If you wish to switch between 27MHz and 2.4GHz, use a SPDT switch. The centre connection would be connected to one of the solder points on the 'Vcc' pad in the picture above.. One of the outer connections would be back to the PCB (one of the 2 solder points on the other side of the cut) to power the crystal oscillator, and to the lifted leg of L5 to power the RF amplifier. The other connection on the switch would be the power line for the 2.4GHz module. Again, there is not a lot of room inside the case - although the 2 extra cells means it's wider than the Mk2, it's not as deep and the stick mechanisms reach almost to the back of the case. If you want to keep the 27Mhz output usable, the only space I can see is to the upper left of the steering stick. If you just want to convert to 2.4GHz, the space between the sticks where the aerial was becomes available.
  23. I'll start at the oldest radio, the AP227 Mk2. My particular radio is a bit battered (the orginal aerial, T-handle and battery meter have disappeared at some point in it's past) but it still works. Unlike more recent radios, it uses 6 AAs, meaning the supply voltage (Vcc) will be around 9V, depending on the type and state of the batteries. My example is fitted with a PCB that is marked 'A42 - 602 - 0' in the copper on upper right corner on the solder side (just below the throttle stick). Any advice below is provided for educational purposes only - any damage, explosions, house fires, injuries or visits from the FCC/DTI as a result of modifying your radio are your responsibility! Here's a picture of inside the radio, the left-hand side of the solder side of the PCB: The PPM output appears on the emitter of transistor Q4 (the output transistor for the PPM section), and can be picked up at the solder points on the pad outlined in yellow. In this radio, the PPM signal is active high, and pulses up to Vcc (9V), which may be a problem depending on which DIY module you choose (some expect 'logic level' inputs of 3.3V or 5V for the PPM signal). The ground connection for the module can be picked up from the large round pad in the upper centre of the picture. To get power for the module, I would suggest sodering direct to the switched power (the bottom of the 3 rectangular pads for the switch just underneath the aerial). There are 2 separate power feeds to the RF section in this design (one to the RF output amplifier and one ot the crystal oscillator). To disable the feed to the output amplifier, I would suggest cutting the track at the yellow line between the switched power pad and the large circular pad to it's left (use the back edge of a scalpel blade to scratch through the copper in a straight line repatedly until the PCB material can be seen). To disable the power for the crystal oscillator, heat the solder on the right-hand pad of resistor R5 (the side connected to Vcc) and use tweezers or pliers to lift the leg from the hole. The above solution would leave the RF section permanently disabled. If you wish to have it switched between 27MHz and the 2.4GHz module, a SPDT (Single Pole Double Throw) switch could be used. The centre connection would be connected to the suggested power point (the powr switch) from the PCB. One of the outer connections would be back to the PCB (the other side of the cut) to power the 27MHz RF amplifier, and to the lifted leg of R5 to power the oscillator. The other connection would be the power for the 2.4GHz module. The only other observation is that it may be a challenge to fit a 2.4GHz module in the case if you want the option of keeping the 27MHz RF section operational. This radio is a bit smaller than later ones (mostly due to using 2 less AAs) and the only place to fit a DIY module would be the back half of the case in the area behind the stick mechanisms, or if the existing aerial is removed the space between the sticks could be used.
  24. Yes, the 2PL is very easily converted, having a separate PCB for the RF section so the PPM and power connections are easily accessible. Unfortunately Acoms were not so considerate
  25. I have a number of different transmitters, so as part of my investigation I opened them up to identify the encoder type and try to find the PPM output.to see how easy or hard they would be to convert: 1) Acoms AP-227 MkII Probably the definitive vintage Tamiya radio (here in the UK at least). Given it's age and lack of features, it is an all transistor-based design as you would expect. 2) Acoms Techniplus AP-27 MkV This classic chrome-plated unit from the early 90s. The circuit design is almost identical to the ancient MkII (basically the only difference is the addition of the servo reverse switches). 3) Acoms Techniplus Alpha AP-201 Acoms (or JR) finally updated their design - this is based on the Oki L9362 chip (this means that if you use it as the basis for a 2.4Ghz mod, you could also potentially add the 2 extra channels the chip is capable of). 4) Acoms Techniplus AP-202 (rebadged JR Propo Beat Sonic) A backwards step. The Oki chip had gone obsolete by this time this was made, so JR/Acoms went back to the all-transistor design of the AP-27 MkV, but converted to surface-mount components and with an additional PCB to provide the LED battery meter. 5) Conrad Razor X4 (rebadged Acoms Techniplus 4 AP-401) This is a more modern 4 channel radio, and the encoder is based on a Mitsubishi microcontroller. On closer inspection of the PCB, it had some unused switch connections, pads for a trainer socket to be fitted, and the silkscreen printing on the PCB indicates it was actually designed by JR. Armed with this information, I did a search on the US FCC database and managed to find the schematics for the JR Quattro transmitter. On comparing the schematic to the AP-401 PCB, it appears to be a cut down version of the JR radio. It uses the same version of the Mitsubishi microcontroller, but the PCB layout has been simplified to remove the tracking and pads for channels 5 and 6 that were present on the JR Quattro. A bit more research showed that the radio was originally sold in the USA as the 'Expert 4' by Horizon Hobby (the US JR distributor). Expert was a high-end american radio manufacturer (similar to Fleet Systems in the UK) who folded and the name was bought by Horizon. It looks like they asked JR to design an entry-level aircraft radio (hence the presence of the trainer port) to be sold under the 'Expert' brand, and JR produced a cost-reduced version of the Quattro as a result. JR subsequently licenced this design to both Acoms and Conrad as a 40Mhz surface radio (minus the trainer port) to be rebadged under their names. The schematic for the 'Expert 4' is also available from the FCC database and matches this radio almost exactly (apart from the omitted trainer port components) 6) Sanwa Dash Saber Dates from around the same time as the AP-202. With Sanwa being one of the better names, you would think they would have an 'encoder on a chip' or microcontroller-based design, but it's obviously been built down to a price and so it's another transistor based encoder. Very similar to the AP-202 design, but with a much more confusing PCB layout. 7) Graupner MC10 'Computer Radio' built by JR for Graupner's German/European market with all the modular features that market expects (though the MC10 is the bottom of the 'MC' range). As it's name implies, it's microcontroller-based, though thanks to it's modular design and being sold in both air and surface frequwncies there is a PCB connector for a trainer socket so the PPM signal is easily accessible. 8) Graupner C4-X (rebadged JR Propo Beat Gear) Early 90s bottom of the range JR 2-channel unit (the predecessor to the Beat Sonic/Acoms AP202), rebadged for the European market by Graupner. Like the Sanwa Dash Saber, you would hope JR would be above using transistor-based encoders, but unfortunately not. The circuit is very similar to the Acoms AP-27 MkV (which was probably derived from this JR design). After opening them up, studying the PCBs and poking about with the oscilloscope, I managed to find whereabout on the PCBs the PPM signal could be accessed. That will be in the next update.
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