Technical

Hello all,

It was mentioned during the recent AGM that loco PCBs (circuit boards) are in short supply, so we discussed the option of having one commissioned.

I have upgraded a circuit board to use a solid-state relay rather than the Hornby electro-mechanical one. I also switched to using LEDs rather than filament bulbs. The main reason was to reduce the size of the PCB and lights. This was done as part of my Royal Scot project where I moved the PCB to the back of the tender, as the loco is so much shorter than an A3/A4.

I tried various relays before settling on the LCB710. The relay has to be normally closed, allow current in both directions and cope with the in-rush current to the regulator motor. The in-rush rather is higher than I had expected; several smaller relays failed due to that. The data sheet shows this one is capable of 1Amp.

One other problem - the relay reacts too fast. I had to add another small smoothing capacitor after the rectifier for it to work reliably. The original electrolytic capacitor was not fast enough. Having done that it seems fairly happy with either LiveDrive or original Hornby controls. Obviously this is only a one-off sample, but it shows that it is fairly simple (even for me) to bring the PCB up to more modern technologies.

What do we all think ?

David