This Teledyne unit was removed from Haywards Heath Railway Station sometime in the 90’s. The control unit was lost when the control room was demolished. I couldn’t find any info about it on the net, so it’s an interesting reverse engineering project. It apparently had three dials that the platform staff could set which would then flip the cards until the correct destination was shown.
Each sign has 4 units, 2 on each side. There are 2 sets of about 50 twisted pairs in and out to control multiple units on each platform. Each unit has two 24V relays, one is set high for the bank and the other low for the groups.
There are 4 banks and 10 groups to display a total of 40 destinations / messages.
There is an A/B (top and bottom units) select and a latch that ensures that the relays on the on-board controller can rotate the display using a 24V DC Motor.
Arduino MEGA 2560 controlled.
There is a 24V relay for each of the 10 groups, 4 banks, the A/B controller, and the latch.
There was an interesting gotcha. I wrote the code on my desktop but needed a laptop to program it in the workshop.
My laptop was on the fritz so I borrowed the kids laptop to program the sign controller. It’s running Puppy Linux, the latest Arduino software installed, but wouldn’t run, so I went with the available option in the software manager. That happened to be version 1.0.0
When the relays didn’t fire (they needed 5V) I checked the voltage on the pins and it was 0.5 volts. After digging into the documentation on pinMode I found out that the internal pull-up resistors get set (but only on version 1.0.0).