Newcomer's technical question about servos

Peter Martinez

Hi Gary:
I have posted this question elsewhere on your forum, but no replies.

I want to use an RC servo for a non-model project (automatic adjustment of a grandfather clock). I understand these servos work by giving the signal line a 1 msec pulse to go full left, 2 msec to go full right, and pulses between 1 and 2 msec to set it anywhere in between. What I want to know is what happens if the pulses stop completely? Does the servo stop where it was last set? That's what I would like it to do. I even wondered if I just give it a single pulse of (say) 1.33 msec, will it jump to 1/3 travel and stop there. Maybe only the digital servos would do this. I don't mind if the motor powers-down and stops "holding" the output shaft once it has stopped, but I definitely don't want it to go back to centre or to one end if there are no pulses.

Do you know either (a) the answer or (b) a man who does? If (a), can you tell me which HK servos I should be looking to buy.

Regards
Peter Martinez

WTWUK

Yes servos will do that. If the signal stops they stop where that signal put them.

Peter Martinez

WTWUK:

Thanks for your answer. I now have here an HK15178B which arrived today. There's no documentation with it. What I would like to know now is the wire connections. The wires are coloured yellow, red, brown, and I need to know which is -ve, which is +ve, and which is signal. I can't find this anywhere on the HK website and I don't want to guess and hope!

regards
Peter Martinez

WTWUK

Red +V, Brown -V, Yellow Signal.

The colours used are JR standard.

You will also find servos with Red +V, Black -V and White Signal which is the Futaba standard.

There are other configurations, but they are rare.