Blog Image


About RelayRepRap

This project is about exploring whether it is possible to make a RepRap control system that can be made by a RepRap.

Toggle circuit using 3D printed relays

Relay circuits Posted on Sat, March 12, 2016 22:47:32

This video shows a toggle circuit made from 3D printed relays:

Here is the circuit diagram:

Here the downward pointing arrows represent 0V, the upward pointing arrows represent a voltage twice that required to activate a relay.

The toggle circuit failed fairly quickly (<100 operations) because
relay C is switching the coil of relay A and this causes arcing at the
normally open terminal of relay C which welds the contacts closed.

I found that this particular design of relay fails after a few 10,000s of operations even when switching non-inductive loads. Generally it fails by remaining closed after power is removed from the coil. I haven’t yet worked out what the failure mode is, but some possibilities are:

– PLA creep, reducing the force that pushes the moving pole back to the normally closed contact.

– Magnetization of the coil nail, causing the pole to stick on the normally open contact.

– The pole nail become loose.

A counter and clock divider circuit

Relay circuits Posted on Sun, February 28, 2016 23:55:50

This video shows a counter circuit that I hope will form the basis of a simple punched tape driven system for controlling the speed and direction of a pair of stepper motors.

The punched tape will have a simple mask for each motor for selecting the speed (1/1, 1/2, 1/3 or 1/4 of the clock rate) and direction. A third mask will be used for specifying the count of the modulo 12 counter on which the punched tape should advance to the next position.