Sparkfun Arduino Pro Power Problem

Forum 2005-2010 (read only) Hardware Troubleshooting
1

I developed a tachymeter based on a hall effect sensor and the arduino Duemilanove board. It worked fine.

I ported it to an arduino pro board. (5V 16MHz) When powered from a USB port and a basic FTDI breakout board it works fine.

When I attempt to run the circuit directly from a battery or a 6V wall wart, (to the power or battery inputs on the pro board) ie no break out board; the circuit does not work. Voltages measured at the VCC pin are low, around (1.3V) and the power LED glows only dimly.

I have downloaded other sketches to the board and these will not work when powered from the battery or wall wart. They work when powered through the breakout board.

I tried this on a second Arduino Sparkfun Pro board and got the same result.

Any suggestions.

Iain Grant

2

how much current is the wal wart rated for?

3

6VDC in might not be enough to go through the voltage regulator and make a nice steady 5VDC for the logic.

The product page says,

Input Voltage 5 - 12 V (5V model)

However, I think it's more likely accurate to say

Input Voltage 5 V pre-regulated **or 7-**12 V raw unregulated (5V model)

4

I glanced at the web page and schematic and didn't see the regulator specs. Worst case, allow for 7.6V (2V overhead for 7805 + 0.6V diode drop).

-j

5

Thank you. Wal wart: Nominal output 6V 500mA, Measured output 8V.

Iain Grant

6

Nominal output 6V 500mA, Measured output 8V

Sometimes the no-load voltage is pretty meaningless. Try measuring it under load (e.g. at the 9V pin of the arduino).

-j

7

When I attempt to run the circuit directly from a battery ...

Was it a 12v car battery? Fresh 9v battery?

8

I totally missed that you said you were using a 5V board before.

As halley said, the board won't work unless you use at least 7V unregulated (or 5V regulated, through the USB port.)

9

I had a similar problem, and it went away when I powered the board with voltage closer to 5V (from 4 rechargeables) rather than 6V (from 4 fresh AAs).