Thankfully i dont have any passengers to freak out. This is one of the circuits for my pinball machine (i dont think i mentioned that yet). I do plan to add a visual test where each bulb can be set to flash by itself and a picture on the screen will show where the bulb should be. I only plan to use that for testing new bulbs when i put them in (or for short circuits). There will be hundreds of bulbs so the automatic testing would really help. If a bulb blows then nobody is at harm so its safe enough to let the circuit decide where the problem is. The bulbs i have dont short out when they blow. They simply break the circuit
PICante, your idea sounds like one of those that i suggested. The basic idea is put an ammeter in the circuit to test if it draws more current when a bulb turns on. In theory it sounds good because the bulbs can be tested while they are in operation. The circuit knows how many bulbs are on and how much current to expect. They would still need turning on individually to identify the blown bulb though. I plan to put the check on startup and run it again every 24 hours and have an option in the operators menu.
Melanie, Im not sure i fully understand your method. I do have 1 pin for each bulb but only to turn it on and off (rather than multiplexing). Are you saying to use those same pins or do i need extra pins? It does sound like it needs a lot of extra components too. Each PCB is designed to control 22 bulbs.
Since i posted this thread i made up a quick design using the relay method because im more familiar with relays than the ammeter way and i didnt know about your way Melanie. Ive uploaded screenshots of the board. I dont mind making it bigger but there can be upto 7 of these plus all the other circuits too. 2 of them are zoomed in so its easier to see and 1 is the actual size of the board. Sorry but its only a PCB layout (not a schematic).
In that circuit the relay gets turned on which switches it into test mode. A resistor holds one of the PIC's pins high. When a transistor is turned on it grounds the pin if the bulb works. If it remains high then the bulb is blown. Ofcourse the bulb will act as a resistor so i will probably have to change the value of the biasing resistor. There are also a few mistakes on it that i know about. It was just a quick version to see how things would fit on a PCB.
When i get some small value resistors im going to test out the ammeter idea because i need that for another project anyway. I would like to test out your way too Melanie but im not quite sure how that would be wired.
It doesnt matter if the lights are on or off during testing. Even if it has the capability i probably wouldnt program it to test during normal operation anyway
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