On-site Integration

[TerryJC]

we noticed this on Monday and added the 4th coach to slow the train down
Geoff had added reflective tape in front of the bogies as he thought it was too close to the track
I get the impression it is an intermittent fault possibly caused by speed
am I right in thinking if the train isnt up to speed when it crosses the sensor then the computer does not read the signal?
could that be changed?
perhaps we need an on site discussion
hope Geoff sees this and responds

Peter,

Speed shouldn't be an issue, because the sensor only has to detect a smidgeon of reflected energy to trigger. The board then holds the signal up for about half a second to give the control system (in this case the Pi) time to react.

If the bogies have reflective material and the sensor pathways are clear, then I'm not sure what the problem is. I can bring a scope in sometime and check that the sensors are actually generating a pulse, but I can't do it yet, because I'm on an urgent job; (the Loos player is on its last legs).

[peter]

Thanks Terry
will check for anything blocking the holes and also get Geoff to check as well

Peter

[peter]

Hi Terry
Appear to have a problem with L298 power supply board
Lighting and signals work OK but no response from Loco ( which is not at fault)
Geoff checked with meter and no power at rails
changed the Board for the spare - worked once there and back then no more
do we need to source another board?
are we missing something ?
could you check please as we are out of our depth!
currently the Raspberry Pi is switched off and only the lighting is on
Regards
Peter Hardacre

[TerryJC]

Appear to have a problem with L298 power supply board

I'm slightly confused here. Do you mean the L298N Motor Drive Board, which is mounted on the Pi Interfacing board, or the PSU Module which provides power to the Pi and the Controller assembly?

Lighting and signals work OK but no response from Loco ( which is not at fault)

Lighting and signals are on a different PSU to the Pi and Controller assembly.

Geoff checked with meter and no power at rails
changed the Board for the spare - worked once there and back then no more

Which board? Does it look like this:

L298D_Motor_Drive_Board.png (769.69 KiB) Viewed 1379 times

do we need to source another board?
are we missing something ?
could you check please as we are out of our depth!
currently the Raspberry Pi is switched off and only the lighting is on

I'll get down there later to take a look, but I need to know what I need to take.

[TerryJC]

Another question. When the Pi was powered on could you see a light on the DC-DC Converter and the Pi?

[peter]

Terry yes its the one in your picture
Geoff put the spare on but the problem seemed to reappear
the board we took off is in the store in the box marked underground spares
I cant get back in until Monday but I shall be on my own as Keith and Geoff are both away now
Peter

[TerryJC]

Did you see the lights?

[TerryJC]

OK. I tested the system on site and couldn't see what was wrong, so I brought the complete assembly home.

The good news is that there is definitely a fault on the assembly, but it's not the Motor Drive Board because I can see the drive voltage across the terminals on the board, but not at the terminals on the TB. I thought it was a dry joint on the Veroboard, but that didn't fix it, so I need to do a bit more testing. I'm sure I can fix it, it's just how long it takes to identify and repair the problem. That's a job for tomorrow now.

I've also confirmed the fault on the Green Traffic Signal which seems to stay on all the time. The most likely cause of that is a 'blown' Buffer IC; highly likely in view of the amount of re-configuring of the wiring that we had to do while we were setting it to work. At least it probably hasn't taken the Pi GPIO pin out, since the IC is there to protect the Pi. Another job for tomorrow.

[TerryJC]

I went back yesterday (twice) but eventually ran out of time.

There were two faults on the assembly. The lack of movement was caused by a bad crimp on one of the wires between the Motor Drive Board and the Veroboard. I did the crimp (and hesitating to blame my tools) we have had problems with these crimps before. The tool is a Chinese copy of the proper DuPont Crimping Tool and unfortunately tends to make a doubtful joint which has to be finished off with snipe nosed pliers afterwards. I posted about it here viewtopic.php?f=15&t=114&p=1729&hilit=crimp#p1729.

The second problem was that a small area of copper on the veroboard had become delaminated. This allowed to copper to touch the adjacent track and turned the green TL on permanently.

Yesterday. I found that I'd made a mistake when I removed the system to take it home. It is pretty cramped under the layout and my knees were giving me stick so I didn't notice that not all of the wires to and from the layout were labelled Peter came in to help and we managed to get the train moving again (initially in the wrong direction) but there are now no Traffic Signals. I ran out of time and had to leave it at that.

I'll be looking into this after later today and am hopeful that I can get it all going tomorrow morning. While I'm there I will label the remaining wires and also create a record for future systems.

[TerryJC]

This activity, to repair the system which stopped working last weekend, has been transferred to the new Maintenance Summer 2019 Topic here: viewtopic.php?f=23&t=158.