Thread: Linking fuse box to pc

Sounds to me like you're on the right track.

Seems like the choices are measuring voltage or current, and voltage is much easier. Current might give some interesting information that may or may not be that useful but it would definitely cost more and be a lot more work. You'd also have the complication of fuse good, but whatever its feeding is "off", so no current - what do you do? Measuring current on both sides would work, but that REALLY gets messy.

You probably have already thought of this, but ....

In the simplest case where you assume voltage is present on the source side, just measure the voltage on the load side. If it's there, the fuse is good. The only complication is do you know there is voltage on the source side? If there are any switches, relays, or other fuses (like a large fuse or ckt breaker supplying a distribution block) upstream, you'd have to check voltage on both sides to avoid nuisance faults and correctly isolate the problem to the real failure. You'd probably want to measure the battery voltage too - useful information if nothing else. That just means more measurement points and a bit of complication to the software.

Fuses don't actually blow that often in my own experience so it may not be that "practical". But if thats what you want to do, go for it. I've done plenty of things that weren't really necessary just because I wanted to.

Yer thats what I was planning to do is check for voltage on the load side of the fuse. The loom on the car is a custom made one that we are doing so I can add the wires no problem and we a grouping all the fuses into a single box.

I think that I can just use a analog to digital converter to check for the voltage and give me an output to send to the computer, what I am strugging with is how do I do this for all the fuses as there's over 20 of them and I cant have 20 inputs on the pc.

I was going to use one of the com ports but how do I group the information together to feed it into the com ports line in and how do I check all the fuses do I have a analog to digital converter for each fuse or is there a way to use one for all the fuses and get a stream of outputs to the computer?

Also we where thinking of doing the same for all the bulbs on the car, I assume that measuring the current is better for this, just check to see if the switch is on and then check for current if the bulb has blown there shouldnt be any current?

Is this post in the right forum by the way I was unsure where to put it, if admin could move it if incorrect.

Thanks

Rich

Yer I just want a fuse warning thats all can you explain the diode circuit, what signal would this send to the pc?

If you went with A/D converter, what you would do is multiplex the inputs into one coverter. Not something you'd probably design and build yourself, but there are modules you can buy with serial interfaces, USB, etc. etc. I don't know if there are any with that many inputs that would be inexpensive though.

If you don't care about the actual voltage, then a couple of ideas are:

1) Use resistor divider networks to produce logic level inputs to some sort of discrete input board or device with enough inputs to go around.

2) Something like this might be what turbocad6 already suggested. What you want to do is create a 20+ input AND or NAND gate. The AND gate would give a true (high) output when all inputs are true and the NAND gate would give a false (low) input when all inputs are high.

You might be able to do something like the diode resistor AND gate here

http://hyperphysics.phy-astr.gsu.edu.../diodgate.html

The inputs A, B, etc. would connect to the load side of each fuse. In addition, you would probably need a resistor from each input (A, B...) to make sure that when the fuse is blown the input is low (ground) and not just an open circuit which might end up acting like a high or a low input and give changing or wrong results. Instead of 6v, you'd use 12vdc. It would take a bit of thought to come up with the right values so components could be selected, but it seems like it should work. The output could then be read by an A/D converter or supplied to a discrete input through a resistor divider network if needed. The trick, especially if you're feeding a discrete input, would be to select resistors to make the output "low" whenthere's no voltage on one of the inputs without ending up having so much current flowing through them when there is voltage that you need big resistors to handle the power.

Thanks for the help upto now guys and I sort of understand what you are talking about.

But electronics arnt my strong point and I dont know how to put the bits you describe together.

Is it possible you could draw me a diagram of how it would fit together ?

Also using the diode option I cant see how I would be able to detect which individual fuse had blow only that a fuse in the box had blown.

If any of you guys need any help with car stereos any time just let me know, just finished our first season of competiton for sound quality and came second, off to belgium in december for the european finals.

cheers