RC Tank Warfare community hobby forum

General Jumbo01 wrote:I'm thinking aloud here, but providing the position of the signal wire is standard, does it matter if the polarity of the servo motor wires are reversed? Presumably the servo will just reverse its direction, in which case you just use your transmitter settings to 'reverse' the servo back?

Otherwise simply unclip the two power cables from the servo plug and reverse them instead.

It shouldn't make any difference unless what the motor is driving/controlling isn't bidirectional.
As the motor will change rotation direction if the polarities are reversed.

Edit: Mind you, after saying that, I don't know if servos have any other electronics inside like a little circuit board
If they haven't, no harm will be caused.
As I've never seen one apart, I'd be interested to find out.

It is my undertanding that you can not simply reverse the direction of a servo by reversing the positive and negative feeds. These wires actually go to a potentiometer inside the servo. Either you have to open the servo and reverse the two wires going to the motor and the two outer wires on the pot or you have to use special servo reversing leads which have some form of circuitry. I am no expert, but those who told me that know a lot more than I.

Ahh, and it has that third wire going somewhere inside that'll need moving.
Bugger, I got all excited thinking/hoping it could be done simply.

I guess not at least I learnt something today

Although, like a motor, a variable resistor isn't usually polarity dependant. It may be more to do with the placement of the third wire.

I think the pot operated left and right, with the centre being neutral so to speak. That would explain why you have to swap the 2 outer wires. Not sure about that. That is me trying to apply the electrics I learned 50 odd years ago

Third wire? If you mean the signal wire that doesn't move, indeed its always in the same place (see the chart above). I've opened and repaired many hobby class servos. In racing you pay a fair bit to buy fast, hi-torque servos and when you hit something at 60mph plus the steering servo suffers. Replacing broken gear sets is far cheaper than replacing the servo. The circuits relate to the signal lead and the positioning of the servo arm. All servo motors are bidirectional or you wouldn't be able to steer both ways!

I have few old servos so will do some experimenting connecting to batteries to see what happens. If connecting the + and - wire to power will make the servo move then it wouldn't be a huge leap to use this for a recoil system

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It won't, trust me. It requires a signal input generated by the transmitter. A servo motor doesn't just spin.

General Jumbo01 wrote:Third wire? If you mean the signal wire that doesn't move, indeed its always in the same place (see the chart above). I've opened and repaired many hobby class servos.

Yes, we know it's the signal wire that shouldn't move, but where does it go inside the servo? What's it connected to?
When you were taking servos apart to service them, did you notice what it was connected to inside the servo?
It's probably that wire more than anything that would stop polarity change.
Also, when you've had them apart, what else did you see in them apart from the motor and gears?

Ah, I've just looked online.
And answered my earlier question whether they have a little circuit board inside.
It looks like they do have a little circuit board inside, with a mosfet or two that receives the signal. To control the motor, and I would doubt that would like a polarity change.

Edit: servos are quite a neat little device when you look into them.
I'm glad I delved into this now, it's been quite a learning curve, getting me ready for when I want to use them

Found this on youtube you only need to watch the first 1 min and keep your eyes on the servo only has 2 wires also read the reply to Sharons Soldier comment kind of explains the wiring.

https://www.youtube.com/watch?v=Nx_HkLjeMvw