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burakol

Radio for TT01e and TT02

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Hi -

I am a public school teacher sponsoring an after school RC club. We were very lucky to have seven Tamiya kits in the form of TT01e's and a single TT02. We need to buy a radio system for them but not sure about the BEC compatibility that Tamiya ESC is requiring. Will the FLYSKY GT2 suffice? Thanks!

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Can you tell us the model number(s) of the ESC(s) so that we can advise you better please?

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We have the following:

TEU-104bk

TEU-105bk

TBLE-02s

So far this is the radio systems we have

Radiolink RC3

Atomik 2.4ghz not sure what model

A china brand 2.4ghz FHSS

And we have three AM radios that we are not planning on using but may eventually do if we cannot afford to buy new radios:

Tactic AM

AE AM from a TC3

Traxxas TQ

We pretty much need 5 more sets to buy but we are running dry of funds...

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The TEU-104BK has no built-in BEC, and is best used with an external BEC, or a receiver that has a BEC built into it.

The other two ESCs have built-in BECs, and can be used with any receiver.

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Since the Flysky receivers don't have their own built-in BECs, they would work fine with the BEC-equipped TEU-105BK and TBLE-02S, but you would need a separate BEC if using them with the BEC-less TEU-104BK.

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Sorry to but in but what is BEC?

Ripped from Wikipedia, the example given applies to RC planes but the principle is the same for cars:

"In an electric-powered radio controlled model, the BEC is typically part of the electronic speed control (ESC). BEC allows such a model to carry only one battery (the motive power battery) instead of two (motive power, and a separate battery to operate the R/C equipment). A BEC-equipped ESC meant for airplane use often incorporates a low-voltage-cutoff (LVC) circuit which can sense the voltage drop caused when the battery has little charge left in it. It then cuts the power to the 'drive' motor in order to provide the 'steering' servo(s) with enough power to be able to bring the model safely back to the operator. The power to the propeller would be cut but the operation of the control surfaces would be maintained in order to perform a dead-stick landing. Without this feature, all control would be lost when the battery expired, probably resulting in the destruction of the model. In some cases, the BEC is part of the radio control receiver, instead of being part of the ESC."

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So for car purposes do we care much?

We would notice the lack of turning and stop the car, not as vital as a plane?

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I should have expanded a little more as the low voltage cutoff is only part of the story.

In RC cars that run 7.2-7.4v batteries, the BEC also regulates this down to a maximum 6v to protect the servo (receiver batteries used to run at 6v). Supplying a servo regularly with full 7.2v battery voltage could potentially damage the servo. Hope this helps clarify further why it's an important thing to have.

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Indeed. Put simply, a BEC is a voltage regulator that supplies the receiver and servos with 6V, protecting them from getting fried by the full 7.2V from the drive battery.

Usually either the receiver or ESC comes with one built in, but in cases where neither have a built-in BEC, you need to add a stand-alone BEC to the system.

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Oh, and as for the glitch question, running multiple Flysky 2.4GHz radios together shouldn't cause any issues. The radios aren't the greatest in terms of build quality (as one would expect given their price), but they are pretty good in terms of their ability to shrug off interference from other radios, other Flyskys included. They are quite popular at my boat club, where at any given time there might be 10 or more operating simultaneously with no problems.

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FHSS and GFSK refer to different aspects of the radio's operation. FHSS refers to its ability to hop frequencies in order to avoid interference. GFSK refers to the filter used to reduce the breadth of the spectrum used for transmission, which is used by a great many 2.4GHz devices e.g. DECT phones and Bluetooth modules.

Different radio manufacturers have different acronyms for their interference-dodging technology, for example Spektrum use DSM2, etc. However from the hobby-level user's point of view, they all seem to work well enough, and many of the supposed differences are nothing more than marketing blurb.

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Thanks for the clarification. Would there be other recommendation besides the flysky gt2 radio that are within the same price point? How about those radios that dollarhobbyz here in the states are selling? Apparently those came from an rtr vehicles...

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I am not sure which radios you mean - Dollar Hobbyz seem to have quite a range. Could you perhaps post a link?

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I have just got one of these turn up through the post

http://www.ebay.co.uk/itm/131299487801?_trksid=p2059210.m2749.l2649&ssPageName=STRK:MEBIDX:IT

Looks good at first glance ( throttle seems not to be spring loaded but sure that is a setting so where)

£20 with receiver from China.

EDIT: popped the back off and swapped a couple of springs and now the sticks function correctly

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I am not sure which radios you mean - Dollar Hobbyz seem to have quite a range. Could you perhaps post a link?

I was looking at the one that came with the cen 1/8 rc... this one

http://www.dollarhobbyz.com/part-type/transmitters/cen-racing-1-8-gst-7-7-3-ch-transmitter-3-ch-receiver.html

Or this one

http://www.dollarhobbyz.com/part-type/transmitters/axial-1-10-scx10-ram-power-wagon-2-4ghz-ax-3-2-ch-radio-transmitter-ar-3-receiver.html

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I have no personal experience of the CEN one, however the Axial one appears to be a rebadged version of the radio supplied with many of the Ansmann buggies.

If this is indeed the case, it is a basic but solid radio set that is simple to set up with the adjusters that hide beneath the sliding cover on the top of the transmitter. It has no model memories, but as you are having one car per radio, this shouldn't be a problem. If anything, the lack of complication could be seen as a good thing.

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If a receiver has a battery port, does it necessarily mean it has a built in bec? Im trying to find out if those radio sets have bec in them but could not find any info... i did however, see that it has a port for a battery plug...

So far, we will have at least 3 cars that will be using the teu104-bk esc... what can you recommend that you are certain of having a built in bec on the receiver?

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As you assumed, a BAT port on the receiver doesn't always mean it has a BEC. E.G. most older 2.4GHz receivers are lacking BEC, and some modern still do.

If the BEC feature isn't advertised in the specifications, then it most likely means it doesn't have such a feature. However, there's another hint for BEC: Have a look at the specs for supply voltage: A receiver without BEC may only be powered with 4.8V to 6V. Receivers with BEC may be supplied with higher voltages. Your racing pack batteries operate in the 7V to 8V range, so a BEC-receiver needs to be able to deal with that. It will also transform the high battery voltage to a 4.8V to 6V range suitable for the steering servo.

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Another way to be sure that a given receiver has a built-in BEC is to look for the BEC logo on the case, which is an oval with the letters BEC in it.

Some BEC-equipped receivers don't have the logo, but all receivers with the logo have built-in BEC.

As for modern 2.4GHz radios with BEC-equipped receivers, I know most Spektrum surface receivers can happily handle up to 9V, but they might be a bit expensive if you are on a tight budget, and I'm afraid I don't know enough about the low-budget sets to tell you one way or the other. Probably best to check the specs as GregM says.

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Thanks... i was able to buy a radiolink rc3 for less than 34 shipped on ebay but after doing some research, i could not find info about it having a bec... but the manual states the receiving can accept up to 10v input...

On another note, i read on the 104bk manual that it is capable of running a lithium battery for it has a built in low voltage cutoff. Does this mean we can use a 2s lipo pack? Ive read conflicting info that tamiya esc does not take lipo, rather it takes life???

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Sounds like you'll be safe with your choice of radio then. 10V input means it'll handle NiCads, NiMH and 2s LiPo without a problem.

Tamiya ESCs can all take 2s LiPo. They can handle the slight voltage increase without a problem.

However the built-in cutoff is calibrated for LiFe batteries, which have a lower safe discharge level than LiPo. By the time it kicks in, your LiPos would be over-discharged.

For this reason, it is wise to run a separate LiPo cutoff or alarm, to avoid over-discharge.

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