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Ask an Expert Forum Press ON - Hold OFF Latching Circuit
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Press ON - Hold OFF Latching Circuit

milosrasic98
milosrasic98 over 1 year ago

Hi!

For a project I'm working on, I want to turn it on and off using only a single button, but in such a way that when you press it turns ON, but for you to turn OFF the device, you need to hold it for a longer period, let's say 5 seconds for example. I was just wondering if you have any circuit ideas that you would like to propose. I've been looking online already of course, and have found one circuit that I will be trying, it's on this link:

http://www.mosaic-industries.com/embedded-systems/microcontroller-projects/electronic-circuits/push-button-switch-turn-on/latching-toggle-power-switch

Fig6

So my list of requirements for it would be:

  • Press ON
  • Hold OFF
  • (Almost) No power draw when OFF since my idea is for it to be battery-powered
  • I would love to read the state of the button with a microcontroller, but the microcontroller can't be used for the latching part, I'm already stretching the MCU thin, and I would need to add an IO expander which I would rather not do at the moment.

Thanks for any tips that you have!

Milos

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Top Replies

  • dougw
    dougw over 1 year ago +4
    This circuit only consumes leakage current when off... You might need a diode in the gate path of Q3 and a pull down resistor on Q2.
  • misaz
    misaz over 1 year ago +4
    Look at MAX16150. It includes almost all you need in tiny SOT23-6 (or WLP) package.
  • genebren
    genebren over 1 year ago +3
    I have used a power latching circuit in a lot of my designs. But instead of adding extra circuitry, I used existing circuits with a few added components. This works given that there is a need for a microprocessor…
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  • colporteur
    0 colporteur over 1 year ago

    I'm not sure of what the signal is feeding but have you considered software control.

    I have varied the length of a button-press when feeding a Raspberry Pi's GPIO. Your discussion didn't speak to what the button is feeding. If the button is not feeding an input that is programmable then my suggestion can be thrown out with the bath water.

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  • colporteur
    0 colporteur over 1 year ago

    I'm not sure of what the signal is feeding but have you considered software control.

    I have varied the length of a button-press when feeding a Raspberry Pi's GPIO. Your discussion didn't speak to what the button is feeding. If the button is not feeding an input that is programmable then my suggestion can be thrown out with the bath water.

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