Servo plus alternative pot.

[Tofer]

Hi!
I’ve changed the kst bls 915 pot for a 10k multiturn pot in order to make a multiturn servo. But it works not the full range of the pot. It starts from 2,5 turns and ends 2.5 turns before the end point. Is there a way to make it work full range or I have use a 5k pot?

[Wawa]

Try a 2k2 resistor in series with each end terminal of the pot (not the wiper).
Leo..

[Tofer]

Well, I’ve solved the problem. I’ve measured resistance in end positions and calculated the additional resistors for contacts 1 and contact 2. So, now it works full range.

[vinceherman]

Tofer:
Well, I’ve solved the problem. I’ve measured resistance in end positions and calculated the additional resistors for contacts 1 and contact 2. So, now it works full range.

Way cool! Got any pics?

[Tofer]

First I want to try to find this parasitic resistor inside the motor. I think they’ve just add a parallel resistor inside to narrow the angle. Ive measured the resistance on the 1st and 3rd contacts without a pot. It is 5kohms. I think I can just remove it and it will work without any additional resistors.

[Tofer]

What I did, I put 2 smd Bourns 11 turns 10k pots on each end pin to make the ends adjustable. But it is real hard to catch the ends. It is very unstable. One time it stops, next time it moves a little. Any ideas why it behaves this way? And a picture is in an attachment.