A relay board  for the Raspberry Pi and the Velleman P8055 interface

It was suggested to me that what this site really needs is a relay board, so here it is. The relay board

I didn't bother with a circuit diagram as the layout is rather straightforward. There are thee relays - in this case I picked the 6V type. Each relay has two change-over switches. These are connected to the three terminal strips closest to their relay.

There is an LED  in parallel with each  relay because when developing a program, it is often useful to see what the relays are doing without having to connect anything to them.

There are three diodes to take care of the back emfs of the relays. Strictly speaking, these aren't necessary as the Darlington drivers used with the Velleman board - as well as my interface board - have built-in back emf diodes. I included them just in case the unit gets connected to some other - non-protected - interface.

There is a fairly  wide bare PCB space between the low voltage and output voltage parts of the board. So as long as one uses suitable PCB material, mains operation should be no problem.

The PCB layout - as seen looking through the board - can be admired below.

The pcb layout

Below are three files which might be useful.

GIF file of the PCB layout

Simple BASIC 5 test program for the Raspberry Pi

Simple BBC BASIC for Windows test program and executable for the Velleman K8055 board

PCB layout drawfile for Raspberry Pi users

Back to the Pi interface section 

Back to the Velleman interface section 


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