8051 reset problem


I have a circuit for an 8051 type microprocessor which executes a 1 minute program and then shuts down completely. I would like to then have a touch switch which resets the power supply to begin execution again. I find that cutting the power supply and then re-connecting the power supply works, but I need to cut the power supply for about 30 seconds before it will reset.

Since I want the battery to last a long time (e.g. a year or more), I would like to take this shutdown approach rather than an interrupt approach. But, I would also like to use a touch switch to reset rather than a hard off/on toggle switch.

Any suggestions?

Many thanks

-- Sean

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30 seconds? That's a long recovery time.

You shouldn't need to interrupt the power supply.

Doesn't your processor have a reset pin? Can't you wire a push button into the power-on reset circuit?

The reset signal is often taken from the junction of a resistor and capacitor, connected in series across the power supply. The manual reset button is then connected across the capacitor.

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Andrew Holme





try using a SR-flipflop of the 4xxx C-mos series (eg 4013) these use only uW of power if static use the output to control a transistor that switches on the power line have the reset controlled by the 8051 have the set floating or weak-preset towards the touch switch (don't forget clamping of the "floating input" to avoid damage! )

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Thank you for the answers, guys! I have enough to proceed.

-- Sean

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