PM20 wiring

[andy757]

Yes but either way, the LED goes out when I try to activate switch 3 and none of the others then work. Disconnect 3, and the others work so maybe another faulty switch maybe ?

I've checked the solder joints and all clean and nothing touching any other terminal.

[Brian]

Suspect possibly the contacts in the switch are not opening when the switch is self returned to the middle Off position? Or you have a locking type switch in the mix?

BTW. Do allow time (a couple of seconds) between any switch operation, this allows time for the CDU to fully recharge.

[andy757]

All switches are the same. Would upgrading the common wire make a difference?
Clutching at straws here.

Or I have some duff switches.

I always allow time for the cdu to recharge.

[Brian]

Possible duff switch? Which ever switch appears to cause problems keep it aside and only use others.

The wire from CDU positive output to each switches centre tab should be 16/0.2mm minimum.

Common return wire from layout motors to CDU output Negative terminal needs to be 16/0,2mm and larger if two motors move from the same switch.

[andy757]

The problem appears to move along. I fixed switch 2 by changing it. Then switch 3 doesn't work.

It seems that any more than 3 switches causes a problem.

I'm going to change the centre tab wire. Maybe overkill but I have some power lead with an overall diameter of 3.3mm rated at 21A.

[Brian]

16/02mm should be more than ample for all feeds to middle tabs of each switch.

[RAF96]

Sometimes you can’t see the wood for the trees.
Are you sure you have your switches wired in parallel and something hasn’t slipped into series in there.
Rob

[andy757]

I've wired each switch so far as per Brian's diagram. Switch 1, 2 and 5 work fine. I haven't got round to 4 yet. For switch 3, wired exactly the same as 1, 2 and 5, and as soon as I connect the green wire for that switch, the others stop working and the green LED on the CDU goes off. If I remove switch 3 green lead, 1, 2 and 5 start working again.

So, 1, 2 and 5 work fine.

Connect switch 3 as per 1, 2 and 5, and they all stop working.

I've checked the underside of switch 3 and can see nothing out of the ordinary i.e. no stray wire touching another terminal.

[Brian]

I've wired each switch so far as per Brian's diagram. Switch 1, 2 and 5 work fine. I haven't got round to 4 yet. For switch 3, wired exactly the same as 1, 2 and 5, and as soon as I connect the green wire for that switch, the others stop working and the green LED on the CDU goes off. If I remove switch 3 green lead, 1, 2 and 5 start working again.

So, 1, 2 and 5 work fine.

Connect switch 3 as per 1, 2 and 5, and they all stop working.

I've checked the underside of switch 3 and can see nothing out of the ordinary i.e. no stray wire touching another terminal.

The GREEN WIRE must not be on the switch. It is the return wire for PM20 motors. Only the RED and BLACK wires connect to the outer tabs of the point switch of a PM20 motor. GREEN connects to all the other Green motor wires on the layout then one wire runs back to the CDU Negative terminal.

[andy757]

I've done away with the wire linking each switch centre tab. Instead, I have connected a green wire from the centre tab to a block which then connects to the CDU negative.

Points 1, 2, 3 and 10 now working. Connect 5 in the exact same way and everything stops again.