Stamp Not Recognizing

tweek.3867

So I've recently begun working a lot with some basic stamps as part of a robotics project I'm working on. Right now, I'm looking to transmit data wirelessly using two Parallax Transceivers. All was going well and I was having no real issues with that.

However, in the middle of testing my code for some of the wireless nonsense, my stamp stopped recognizing. I've gone through and tested it out the best I can-- there was a short on one of the breadboards I was using due to some sketchy pins being used to connect the serial cable to the breadboard, but replacing it with a nicer pin fixed that. Just the same, though, it still isn't working. I know the serial cable and computer serial port both work, as I can plug the cable into my robot and program it no problem. The batteries are all putting out 9v and everything.

When I plug the battery into the boards, though, anywhere at all on the breadboard, the most I can receive is 6v, often hovering between 4 and 5, even though when the battery is checked directly, it is indeed putting out 9v of power. If I try to plug in a stable power supply to the board, even when I set it to 9v even, the second I turn on the DC out and have it start putting power into the board, it immediately gets dropped down to 6.3v and fluctuates [noparse][[/noparse]lower, never higher].

I'm kind of clueless as to where to go now-- I know it isn't the breadboard itself, as I've tried it on another breadboard to no avail, and I hope it isn't the chip itself, as I have two, neither of which work, and both were opened brand new from the wrapper yesterday (they are both BS2px24).

If anyone has any ideas, it would be amazingly helpful. Thanks!

-Phil

allanlane5

A 9-volt battery, measured "open-loop" (just putting a voltmeter across the battery) can give you false positives. What you really want is to measure the battery voltage when in-circuit. If when in-circuit the battery is NOT giving you 9 volts, then the battery is worn out.

Now, if a really good voltage source (like plugged in to the wall) is being "drawn down", then you're drawing too much current from that supply. This can happen if the supply is too small (it CAN put out 1 amp, right?) or if you have a short on your board, or if you're trying to drive something that's really current hungry (like a motor, or even a Transciever).

One fast way of resolving where the problem is, is to build a "minimal" breadboard with JUST the BS2 module on it. Make sure you can 'talk' to that setup -- now you KNOW the power supply is good, the module is good, and your cable is good. THEN you can add one piece at a time until the 'talk' fails -- the last piece added is the problem.

You MIGHT set your voltmeter to measure amps (or milli-amps) and put it in-line with your power supply to find out just how much current you ARE pulling from your supply.

tweek.3867

Ah, yea. I was actually making a simplistic board, like you described, as you posted this. The second I plug the serial cable onto the board, I can see the voltage drop on the dedicated power supply.

I know the supply works as we actually use it to power a quadrotor helicopter that one of the other guys is working on when it's locked onto the table for testing that uses far more power than my current project ever will.

I had noticed there was a short between two of the serial cable input spots on the board; is it possible that that is what is causing the power drop? I suppose it would be kind of strange for that, though, seeing as how this is happening on two separate breadboards.

BLARGH. How frustrating.

I'll try to mess around with the power supply a bit more-- make sure it is producing as well as it should be.

Thanks for the advice!

allanlane5

Yes, a short on the board (ANY short on the board) could be causing this, even a short on pins on the Serial cable.