I ran into a snag with my decTOP, which I was planning to use as a radiation monitor: it does not power itself back on after a power failure. This should be changeable in the bios, but it’s inaccessible and emails to Date Evolution have gone unanswered. The power pin is normally 3.3v, and powers up on a rising edge (i.e. you have to release the button before it will start). I described this to Mike Fincham, and he suggested I connect a resistor and capacitor in series, from ground to the power-up pin. The capacitor acts as a switch. When power is first applied to the decTOP, it will begin charging, connecting the power-up pin to ground. When charged, the capacitor stops conducting, allowing the power-up pins voltage to return to 3.3v, and the computer to power up.
It works! The capacitor is obviously a bit large (10 microfarad), but it’s all I had on hand.
6 Comments
Hello,
Thanks for sharing. I have access to the BIOS of the decTOP and there is no option to change the power on feature.
So, your solution is the only one I have found. Please, let us know the value of the two resistors (see in the picture) and the correct value for the capacitor (to place inside the decTOP case, if possible).
Thank you and best regards,
Nibble
The capacitor is 10uF. With the resistors, I think I was shooting for 1K, total.
Dear OWAD,
Thank you for your reply.
10uF x 50V is ok?
And the two resistors, 1K each?
Best,
Nibble
I meant 1K total. I think I must not have had a 1K handy, so I approximated it with two resistors. With different values, all you’re doing is varying the amount of time that the power button is ‘pressed’. It doesn’t have to be exact.
10uF 50V sounds fine. 50V is the maximum voltage, so you’re well within that.
Thanks again!
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