Servo Reverse - Murrells Models

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Servo Reverse


Servo Reverser Version 2

My objective was to create a small servo reverse circuit on Veroboard, keeping the design as simple as possible. I had some PIC 16F628A's spare, a 10cm servo extension lead, a length of pin header (3 pins), two capacitors 0.1uF and a Tant bead 10uF 16v

The PIC runs at 4Mhz on it's internal oscillator, it measures the incoming pulse length from the receiver and then generates an outgoing pulse which reverses the direction the servo should rotate. Program written in Proton BASIC compiler, took about an hour to write, a few hours to test, fault find and then solder up a couple for use.

This circuit has no voltage regulation, the PIC max. voltage = 5.5v so check the output voltage from your receiver, if it's higher than that you will blow the PIC.
Disable ‘Brown Out Detection’ when programming the PIC, this will cause the PIC to reset and give unreliable operation.
The only place that you need to cut the Veroboard tracks is at the two red lines on the diagram, (this diagram is viewed from the top IC side of the board and needs to be reversed when viewing from the track side)

I realise that this is quite wasteful of the PIC and a chip that only had 6 or 8 pins would be a better solution but it was what I had to hand. If you wish to purchase pre-programmed PIC's then get in touch, see email address on 'For Sale' pages.

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