My obsession with flip digits, flip dots just keeps growing and growing. I recently bought several of these large 5X7 flap displays. They were made by a USA company, Americal Electronic Sign Co. They were used in traffic management signs. I cannot find any technical info, manual or schematics, so I will have to have a go at reverse engineering these.
Each unit is 2 parts, the front flap display panel and the rear pcb with the drive coils and the control electronics. I opened two up - one appears good, the other has a burnt out IC and a burned out diode & possibly drive MOSFET
Yuk. I'll inspect a few more panels later, but first to try and figure out how this is wired up and how to drive it.
Each display is controlled by a coil that moves a magnet on the flap, each coil has 3 wires. a common and then 2 separate windings - I assume one to set and the other reset. Nice - much easier to control than the flip-dots that only have one winding and require you to reverse the polarity. Each segment also has 4 leds - these are on stands as you can see in the above pic.
There are 6 wires input. 4 are adjacent on the board and look like power and 2 are separate and look like the data lines.
Red looks like + voltage to power the coils. A label on the rear implies 24v, Black isground. The Green seems to be power for the leds (based on early look at the pcb). The blue I am unsure of - at first I thought it might be 5v logic power, but it looks like the 5v logic comes from the +24v as I have seen a 5v voltage regulator on the PCB. The blue seems to connect to a 6 pin opto isolator QTC4N35 ic. So maybe some sort of enable line? (not sure yet). Edit: I think this is the groud for the LEDs - makes more sense - I think the opto isolator thing is to enable the leds circuits.
I found another pic of a similar board:
This seems to confirm that the 4 together are power and the other 2 are the data?
On the rear of the PCB is an 8-way dip switch
I am pretty sure this is a unit identifier - these will have been strung together, so need a way to identify each one. I also noticed a 74HC688N IC nearby - this is an 8 way dual comparator. I guess it compares the 8 switches with 8 values it received and uses the output to act on the signals if we get all 8 digits matching up! Seems pretty simple.
I'm going to first identify all the Ic's on the board. All components have been covered in a clear shiny protective varnish - making it hard to identify the ic's - I might need to look at several boards to identify them.
Ive identified all the ICS and started an easyeda schematic.
NE555 U9 is a clue - looks like it generates own clock signal to move data from the single input through the various logic chips - invertors, flip flops, shift registers etc. I need to figure out the timing. There are 3 595 SR's - so 24 bits in total.
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