i'm a student from Slovenia and I am working on a project in automotive industry. I get a task that I have to build a system, that will test a bundle like this:
So the situation is like this: On the one side I have signal generator, that produces 12V output signal. The signal goes trought the first wire of the bundle and if the wire is not interrupted the signal generator counts 1 and the signal goes to the next wire 2. If the second wire is not interrupted, signal generator counts to 2 and signal goes to next wire 3 and so on trought all wires (26). The sheme is below:
My idea is to use arduino with transistors as a switches, or using relays for switches. Wich Idea is better?
So the sheme should be like this:
With arduino I would like to do the next tests:
test if the wires are properly connected and they are not confused
test if the wires are not discontinued
Do any of you have some experiance with applications like this? Is there possible to use 12V relays on the digital outputs of the arduino? Should I use some demultiplexors to get enought digital outputs for al wires?
Since an Arduino is able only to control 20 mA per pin, and its threshold is 2.5 V, then that corresponds to 125 Ohms.
What this means, is that the Arduino could not by direct connection, detect a resistance less than about 100 Ohms.
If you seriously want to test an automotive harness, you really want to switch connections using some sort of relay (in the "old days", it was a uniselector) and use a 20W automotive bulb as the load to a 12 V, 4 A power supply.
Make a couple banks of shift registers - TPIC6C595 on one side, 74HC165 on the other with pullup resistor on the inputs.
TPIC6C595 pulls a pin low, capture all the lines with 74HC165 and confirm that only the correct line is low. Repeat.
If no line is low, you have an open.
If a different line is low, you have crossed wires.
If more than 1 line is low, you have a short between wires.
If a line is low when nothing is driven, you have a short to ground.
Don't need 12V for that.
If you do want 12V, then add voltage dividers (pairs of resistors) to bring 12V down to 5V for the HC165s inputs.
TPIC6B595 can pull low from a 12V source.
Since an Arduino is able only to control 20 mA per pin, and its threshold is 2.5 V, then that corresponds to 125 Ohms.
What this means, is that the Arduino could not by direct connection, detect a resistance less than about 100 Ohms.
If you seriously want to test an automotive harness, you really want to switch connections using some sort of relay (in the "old days", it was a uniselector) and use a 20W automotive bulb as the load to a 12 V, 4 A power supply.
Well, that's how I see it anyway.
Tnx very much, I am working on application with relays now and I also did another post bellow ''How to setup all arduino outputs to low when power on''. I will be very happy for all your advices Paul_B !!
