Power Button

Hi all, I am making a battery powered device that uses a Single board computer running Linux. The problem is that because I am using a CF Card mounted read/write I cannot just cut the power to the SBC. So I need to have some system by which the SBC can shutdown properly before it cuts the power. I am thinking of something like the power button on a computer. So does anyone know how I could go about this? A circuit would be great. Thanks

-Kit

Reply to
Kit
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Some idea of the SBC you are using would be helpful, but it must have some kind of i/o capability. Either a serial port, I2C or some kind of GPIO ports must be present regardless of the SBC type. You should be able to read from one of these in software and then initiate a "shutdown -h now" procedure.

Reply to
Anthony Fremont

Sure, I am using a Technologic Systems TS-7200.

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Yes, I can do that, but once the SBC is shutdown I need to turn off the power. Thanks

-Kit

Reply to
Kit

You could use an output pin on the SBC to trigger a one-shot. The falling edge of the one-shot output could then reset a flip-flop that drives the power relay. To start the system, apply power directly to the relay and to the 'set' input of that flip-flop.

Reply to
Stephen J. Rush

Ok, I think I get it now. ;-) Looks like you have a serial port on there. After you do a "shutdown -h now", see if the DTR (or any other status) pin changes state. If so, that could be used as the signal to an external device to turn it off.

Or you could possibly use one of the i/o pins to start a timer that would power off the computer after a predetermined delay. The i/o pin would be toggle from a script that executes during shutdown.

Reply to
Anthony Fremont

BTW, how do you like that board? Is the Linux distro stable (as in runs for months without issue)? I'm looking to use something like as a central controller for a bunch of home automation junk I've come up with. Mostly just to do a bunch of long term logging, yet be accessible over the network.

Reply to
Anthony Fremont

in linux the shutdown process is controlled by the symlinks in

/etc/rc6.d (got questions? read up on sysv-init and/or ask again in a linux newsgroup.)

after it turns off, how is it supposed to turn on ? does the board have a shutdown mode, if so what happens on DIO1 pin 16? and or the USB power terminals, serial port outputs etc...

Bye. Jasen

Reply to
jasen

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Have you checked out OpenWRT running on Linksys WRT54G_?

Runs linux, open sourced, c/w PS, built in GPIO, serial port, 5 ethernet and wireless for under $60!!!

Reply to
Epictitus

So far the board has been great. As for stability, I can't really say. Because I haven't had it for very long, and it hasn't been running for most of the time (I have been trying to get the rest of my project going :).

I figured out what I needed. I just needed a SCR. Thanks for the help anyway.

This isn't related, but I was wondering if anyone has used the Propeller from Parallax? If so what is it like, how well dose it work?

Thanks again

-Kit

Reply to
Kit

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