Powering Stamp from PC Power Supply
dhenshaw
Posts: 7
I have a clock project that is powered by an old PC Power Supply. I power the Stamp off the regulated +5v line and the motors get powered from the +12v line. It works like a charm...
Except that sometimes, if the power gets cycled (like during a power outage) and when the power supply starts up again, the stamp sometimes doesn't initialize properly, and the motors go into a free-wheeling uncontrolled spin. It can take four or five manual power resets for the Stamp to "kick in" and run its program again.
I suspect it's because I'm powering my Stamp (on the BoE) from a 5v line, when clearly it's documented as needing 6 to 9v! But, since my two options are either 5 or 12v, I'm wondering if there might be a solution like:
Any ideas gratefully researched....
Here's what the finished clock looks like...
Except that sometimes, if the power gets cycled (like during a power outage) and when the power supply starts up again, the stamp sometimes doesn't initialize properly, and the motors go into a free-wheeling uncontrolled spin. It can take four or five manual power resets for the Stamp to "kick in" and run its program again.
I suspect it's because I'm powering my Stamp (on the BoE) from a 5v line, when clearly it's documented as needing 6 to 9v! But, since my two options are either 5 or 12v, I'm wondering if there might be a solution like:
- Power the stamp from +12v. It won't burn out...
- Add a little circuitry (maybe something involving a capacitor) to help give the stamp a little "kickstart" when the 5v starts to flow in
Any ideas gratefully researched....
Here's what the finished clock looks like...
Comments
1) A lot of PC power supplies have a minimum load on the +5V supply (and maybe on the +12V as well).· A Stamp doesn't draw a lot of power.· Make sure you have a large enough load on the +5V supply (check the manual for the PC supply).
2) You could run the Stamp off the 12V supply.· The main issue is that, with a +12V input, you have a lot of power to dissipate as heat if there's any significant amount of load on the +5V supply.· The regulator on the Stamp module has no real heatsink which is why it's specified for a 6V-9V supply.· You could easily add an LM7808 regulator to give you 8V from the 12V PC supply, then run the Stamp off that.· Do be careful if the +5V PC supply is unloaded or too lightly loaded in that case.
http://forums.parallax.com/showthread.php?p=723833