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Savöx digital servo issue

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Hi guys.

Striped a model for some electronics and got a nice Savöx SC-1285TG Servo. It works pretty fine on my test setup. I use a random 2.4ghz HPI remote and its receiver which is powered with external 4x1.2V AA cells.

Once I connect the servo with my runner electronic, it just does not work accurate. There is a 7.4V from 2S LiPo and a Nosram brushless ESC. Voltage delivered from ESC is about 5.8V to red & black servo wire.

Thats curious somehow...

Greetings : )

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when you say 4x1.2v AA battery... what EXACTLY do you mean?  alkaline, nimh, nicad?  not all of those are 1.2v

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I think what he is saying is even at the lower voltage the servo worked on his other radio.  So it must be something to do with the signal or conversion..(?)

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That servo has a range of 4.8V to 6V, so the power shouldn't be an issue.  @Willy iine is onto something I reckon, digital vs analog signals. I like those servos and have a few, they are noisy just sitting there, its like they make constant adjustments. Could it be normal operation?

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The test setup is a budget Modelcraft 2.4GHz R3WP radiosystem. On my runner it is a Kopropo Mars with Spectrum 2.4GHz DSM module.

Dot know precisely about the differences of both setups.

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On 10/25/2023 at 3:01 AM, tim.senecal said:

when you say 4x1.2v AA battery... what EXACTLY do you mean?  alkaline, nimh, nicad?  not all of those are 1.2v

4.8V exactly.

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On 10/25/2023 at 1:23 AM, Willy iine said:

Does it have anything to do with analog vs digital servo setup on your radio?

Does it have this settings? Need to read the manual again. It is a Kopropo Mars.

I thought once the signal is at the receiver, the rest is done. Oh boy I know nothing... :blink:

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On 10/24/2023 at 9:18 AM, Collin said:

Hi guys.

Striped a model for some electronics and got a nice Savöx SC-1285TG Servo. It works pretty fine on my test setup. I use a random 2.4ghz HPI remote and its receiver which is powered with external 4x1.2V AA cells.

Once I connect the servo with my runner electronic, it just does not work accurate. There is a 7.4V from 2S LiPo and a Nosram brushless ESC. Voltage delivered from ESC is about 5.8V to red & black servo wire.

Thats curious somehow...

Greetings : )

I have a few of these servos. In my case they needed a capacitor ("glitch buster") for the servo to work correctly. Without it, I would either see the throttle kick in forward or reverse randomly as soon as I touch the steering, or in another case I have had the steering work but in a very imprecise and jittery way - seems to be what you are experiencing? In any case, these issues were completely resolved with the capacitor. It's a very fast and powerful servo and a great choice.

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6 minutes ago, Pylon80 said:

Without it, I would either see the throttle kick in forward or reverse randomly as soon as I touch the steering, 

Like this?

 

On 10/24/2023 at 5:18 PM, Collin said:

Voltage delivered from ESC is about 5.8V to red & black servo wire

It is not how many V but how many A is your ESC providing? Not enough and you will run into problems.

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9 minutes ago, alvinlwh said:

Like this?

It's hard to say when you are not the one handling the transmitter. If I tried to go lock to lock for instance it would go there very fast but not smoothly i.e. jump out of the lock then slow down a bit then catch up and slam to the opposite lock. Hopefully that makes sense.

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16 minutes ago, Pylon80 said:

It's hard to say when you are not the one handling the transmitter. If I tried to go lock to lock for instance it would go there very fast but not smoothly i.e. jump out of the lock then slow down a bit then catch up and slam to the opposite lock. Hopefully that makes sense.

I mean the motor moving/twitching when the servo is moved (with no throttle input).

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so...  back to @Collin's original question.  looking at the nosram esc listings, the high end models are a 6v/6a bec, and the lower end model is 6v/3a...    with the nosram ESCs putting out at least 3a, i don't think its an amperage problem, but i do know that some switching power supplies can be quite "noisy"...

try disconnecting the ESC in the car, using the 4.8v supply you used on the bench, and see if the steering servo still acts funky.  if it DOESN'T,  then you have a flaky BEC in your ESC.  you might be able to get rid of interference (if that is what it is) by wrapping the steering servo wire in a ferrite ring, but that might not solve anything.   a classic "fix" for this that a lot of spektrum receiver owners have used is a "glitch" buster capacitor plugged into a spare receiver servo socket.

https://www.amainhobbies.com/protek-rc-glitch-buster-receiver-voltage-stabilizer-ptk-2950/p450146?gclid=CjwKCAjw7oeqBhBwEiwALyHLM_OvZKJypCTYDG3c-1LDSIrc_tk5d6MmH7UEv8mZD4Jp83SRaIpAzhoCOgAQAvD_BwE

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14 minutes ago, alvinlwh said:

I mean the motor moving/twitching when the servo is moved (with no throttle input).

Yes, I see it now! It was even worse, the car was propped on a stand on my work bench and the motor would start full throttle making the car pitch up and down.

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Lot of usefu input guys. Still sitting in the Pub with my good old  friends Mr. Guinnes and Ms. Bulleit. Will check things next days. Thanks anyway.

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7 minutes ago, tim.senecal said:

with the nosram ESCs putting out at least 3a, i don't think its an amperage problem

I think the 1258 will draw 5 amps easily. This was discussed recently... I got away with a 1080 ESC that's rated at 3 amps only again thanks to the capacitor.

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2 minutes ago, Collin said:

Lot of usefu input guys. Still sitting in the Pub with my good old  friends Mr. Guinnes and Ms. Bulleit. Will check things next days. Thanks anyway.

Say hi to Bulleit for me please!

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Okay so I made some progress. Seem like the ESC is really to weak for the servo. Used the 4x1.2V block instead of the ESC and the servo did it.
Next I will try a capacitor, just to bad I do not have one laying around. Will have a look for a 16VDC 1800uf to see if this might be enough to push up a bit.

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you can always simply disconnect the red wire from the esc to the receiver, that will eliminate the ESC's built in BEC, and then go with a third party BEC,  there are a few different brands out there, with some able to handle up to 20 amps. 

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Must have one new laying around. Will try that becaus found no cap yet.

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21 hours ago, tim.senecal said:

you can always simply disconnect the red wire from the esc to the receiver, that will eliminate the ESC's built in BEC, and then go with a third party BEC,  there are a few different brands out there, with some able to handle up to 20 amps. 

Yeayea. Found a 5/6V 3A UBEC and set to 5V it worked. Funny was that I started with 6V and the servo vorked as long I was steering left to right and so on quickly. Once I stopped the servo did not response anymore.  On 5V its all fine.
Will wire it propperly now and saying thanks to all this input. Worked way quicker to sort things out. I love the Club!

T.

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