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I would like to have a way to reset my PIC by removing power from the chip. My hacker self thinks that the simplest way would be to add a resistor between the output of my LDO and Vcc on the PIC, and then add a button between GND and after the resistor. To avoid any potential issues with switch bounce, I figure I could add a cap in parallel with the button and a resistor in between, like this: (ignore component values, those are the defaults from the editor)

schematic

simulate this circuit – Schematic created using CircuitLab

Is there anything seriously wrong with doing it like this? I'm trying to keep it simple and not require a bunch of components.

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    \$\begingroup\$ Resetting a μC with a pushbutton is usually done by pulling down the reset pin (/MCLR on a PIC). Is there a reason why this cannot be done? \$\endgroup\$
    – jms
    Jan 31 '16 at 19:53
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You'll suffer variable voltage drop depending on load current. It doesn't look too elegant.

schematic

simulate this circuit – Schematic created using CircuitLab

Figure 1. Power cut button.

How about using a normally closed pushbutton? Switch bounce isn't a problem. The circuit will just reset again.

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  • \$\begingroup\$ So basically, even my original idea (before what I had posted), which was what you had outlined, but without the capacitor, would have been a better solution? :) Thank you for your input / insight! \$\endgroup\$
    – Dave
    Jan 31 '16 at 21:28
  • \$\begingroup\$ Now the trick is finding a NC surface mount button... \$\endgroup\$
    – Dave
    Jan 31 '16 at 21:34
  • \$\begingroup\$ thanks for the link, wow that thing is monstrous! I wonder why no one makes those tiny SMD buttons NC? \$\endgroup\$
    – Dave
    Feb 17 '16 at 7:20
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Don't you have an /MCLR pin?

You didn't write which PIC you are using so I'm just cutting and pasting this from a PIC16(L)F1717/8/9 datasheet:

5.5 MCLR

The MCLR is an optional external input that can reset the device. The MCLR function is controlled by the MCLRE bit of Configuration Words and the LVP bit of Configuration Words (Table 5-2).

5.5.1 MCLR ENABLED

When MCLR is enabled and the pin is held low, the device is held in Reset. The MCLR pin is connected to VDD through an internal weak pull-up. The device has a noise filter in the MCLR Reset path. The filter will detect and ignore small pulses

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  • \$\begingroup\$ Sorry, no MCLR, this is actually a PICAXE. \$\endgroup\$
    – Dave
    Jan 31 '16 at 21:26
  • \$\begingroup\$ Aha, bummer... It is a good idea to mention the exact IC in your question. PICAXE-40X2 for instance has a reset pin. \$\endgroup\$
    – Dejvid_no1
    Jan 31 '16 at 21:47

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