Simple Analog Servo Loop

 I am working on a simple proportional servo loop using a 741 Op Amp and a complimentary pair of transistors TIP41 & TIP42.  This circuit and hardware was inspired by n3ox and his web post.

I am using the AdaFruit TT motor --> HERE tied into a ~ 1:3 LEGO gear reduction box that drives the motor position potentiomter.

So far, this is just proportional control but I intent to expand it to full PID.

I have been experimenting with the proportional gain between 5 and 10, higher than that it gets unstable. I am having an issue with very slow changes were it stops moving even if I increase the position pot R1 to a much greater value. Bumping the drive system gets it to correct, so I don't know if this is a stall issue or a "dead spot" condition with the DC motor. I am just using single turn pots that do have a bit of drag and low resolution, I will be switching them out soon with 10-turn units next.

73

ARISS "Amateur radio on Shuttle, Mir and ISS" SSTV event - June 21-26

Receiving ISS SSTV Images from the ISS

ARISS "Amateur radio on Shuttle, Mir and ISS" SSTV event - June 21-26

Myself and several of the folks on our High Altitude Balloon Group copied almost all 12 images that were sent this week. Just a ground plane antenna or even a HT with a rubber duckie could copy the transmissions in most cases.