I've been chasing some strange ghosts with an Arduino project I've been working on.
After experiencing some random and erratic behavior that's been hard to pin down. I happen to put a volt meter on the board that the Arduino Uno is plugged into (designed by an engineer that is no longer with the company, and I myself am a software guy not a hardware guy), and I measured the voltage at 7.4V.
I've read that the Arduino can behave strangely below 7V, but even though my reading shows 7.4 V I bought a 9V regulated power supply and powered the Arduino directly and it seems to have a positive effect in that these random erratic problems we've been having seem to disappear when I do that (I say that because I still have to test further since this is a random thing).
Strangely though, whether or not I use my 9V power supply for the 7.4 V source that is on the board the Aduino Uno is plugged into, the pins on the Arduino itself consistently read 5V. So that would indicated that 7.4 vs 9 doesn't matter? Yet these issues we are having seem to be gone when I power it with 9V.
My next thought was to get a scope and look at the waveform of the 7.4V.
Anyway, I was wondering if anyone has any experience with voltage issues and the Arduino?
I've read that the Arduino can behave strangely below 7V, but even though my reading shows 7.4 V I bought a 9V regulated power supply and powered the Arduino directly
Welcome to Hardware World.. if you have patience, you'll find it fascinating.
The scope idea is good. You have something "like 7.4V" but something "like 9v" seems to,w ork better. This sounds like you're converging on the problem.
Sounds like "once in a while 7.2 V is not 7.2V :. What else is "7.2" powering? What kind of devices are in this system??
The system I'm trying to hook into already has it's own existing wired control pad which is driving a 220V high powered motor.
Currently the Arduino and WiFly RV-XV/Wireless SD Shield combo is piggybacking on top of this main controller board.
There is a transformer block on this board which appears to be bringing the 220V down to 24V and then somehow the Arduino is getting 7.2 Volts fed into it.
The guy that implemented the hardware is no longer with the company, and I was able to ask him about this and he said the 7.2V issue I mentioned was not an issue. But my experimental data seems to indicated otherwise.
I was puzzled why if we have 24V coming off of the transformer, and that the arduino can run between 7 and 12V, that we didn't stay in the middle of that range around 9 or 10. He indicated a heat issue concern as they reason he went with 7.2V.