I bought a couple of Seeduino boards last year. So far I have made a couple of projects with them - always using USB power for them.
I’ve build a power monitor, using a Photo Transistor to count the number of flashes on the electricity meter to monitor power usage. I’m also using a DFRobot ethernet shield to enable the project to support SNMP connectivity.
However…I would like to use the setup with an external power supply rather than the USB power - I’ve tried both a 12v and a 7.5v power supply but with either of them connected the voltage regulator on the board is getting very hot after only a couple of minutes.
Is it normal for the regulator to run hot or do I need an alternative PSU - can anyone recommend a good supply? I have tried a mini-usb type phone charger but this does not appear to run the board correctly - application is not very stable…
The voltage regulator normally runs warm but not overly hot. You should be able to touch it for a few seconds without getting your fingers burned. You may be drawing way too much current. But, if you had been using the USB with it before switching over to a power supply, I can’t imagine what could be drawing so much current – unless you inadvertently shorted something. On the other hand, you could just have a bad VR.
I don’t have a seeeduino, but I do have a few arduino Duemilanove. The VR chip should be similar and should give you 5V out in normal operation. The part numbers on these things are really cryptic, but I was able to find something of a datasheet that should match. See here: http://www.datasheetcatalog.org/datasheet/motorola/MC33269D-5.0.pdf What you described sounds a lot like you’ve reach the device’s thermal limit. See this text in the spec:
As for what power supply to use, I would use the lowest possible supply that meets the minimum power source for the VR. If you’re drawing 5V @ 800 ma (max rating of VR) then you should use a power supply that provides you at least 750ma @ 7.5V.
