Simple Servo Mechanism Using A PIC16F684

This is a simple servo mechanism built for Ethan G. to control a lever. It uses a PIC16F684 to control the back and forth motion, and it is activated when pin 13 (RA0) receives a high logic level (+5VDC).

It took all of about half an hour to assemble the circuit, write the code, and build the mechanism! ;)

Good luck, Ethan!

Category:

Science & Technology

Tags:

• PIC16F684
• PIC
• servo
• mechanism
• lever
• motor

[SamuelAaronWard]

It is also very easy to hack a servo for continuous rotation - at which point it's nothing more than a geared DC motor (no feedback for positioning). All you have to do is cut a tab off of one of the gears, do the same to the inside of the potentiometer, and rewire the pot's wires to a new external pot or resistor. ...If you give it anything less than 1.5 ms duty cycle, it will turn continuously in one direction; anything more than 1.5 ms duty cycle, it reverses direction.

[SamuelAaronWard]

@RStephenLegge - Thanks, Steve! Yes, servos generally require pulse-width-modulated signals with duty cycles (on time) between 1 and 2 milliseconds - and off times of 10 to 20 milliseconds. The duty cycle is what determines the servo's position. ...I have had servos that vary somewhere between 180 and 210 degrees of rotation; and yes, sometimes I've had to tweak the duty cycle beyond the 1 to 2 millisecond range to get the full range of motion - just trial and error 'til I get it right.

[RStephenLegge]

Nice video. I imagine you are sending pulsewidths between 1000uS and 2000uS to get almost 180 degree servo rotation. I was having an issue with a T-Pro SG90 servo that turned out to be wanting 800 to 2300uS pulses. Still can't get a full 180 rotation though. Still waiting for the hand.