Modification on latching power circuit

Question

I have built the following circuit to power my esp8266. And it works fine.

https://community.home-assistant.io/t/multiple-button-wifi-remote-no-deep-sleep-required-battery-lasts-forever/306233

When you press the button esp8266 turns on, and by setting D1 high it still has power even if the button is released. When I do things with my code I set D1 low and esp8266 shuts down.

But in my application when the button is pressed it will stay pressed for some time. I want esp8266 to shut down all circuits whether the button is released or not. If the user releases the button and presses it again esp8266 should power on again.

But in this circuit, if the button is still pressed after esp8266 does its job and sets D1 low, the circuit remains powered.

What can I do to make esp8266 power down even button is still pressed?

I don't want anything with software, sleep mode, etc, I need to solve this with electronics.

Answer 1

Pulling pin Low you hold Mcu powered. Pulling High you disconnect supply. It’s good to add 10u + 100n bypass caps to Mcu Vcc so it live few ms after pulling pin High. A diode is signal schottky.

Answer 2

So you want the circuit to react to the edge, not the continuous state. This can be done by adding a capacitor between the switch and the node of 100k/gate/d1 (Let's call this Vg) right above it.

When you first press the switch, the capacitor is empty. This immediately pulls the node Vg low, enabling the FET just like before.

The capacitor starts charging up through 100k, and at some point it will reach the threshold voltage of the FET which will turn off again.

To make sure it doesn't, the RC time should be long enough for the ESP to boot and pull D1 low permanently.

The ESP can now disable the power regardless of the switch state.

The only thing to fix is resetting the capacitor. When the switch opens, the capacitor has one pin floating, so it doesn't discharge. To fix this, connect a resistor that is at least 10x the size of your 100k (so 1Meg) in parallel to the capacitor. The ratio of 1:10 ensures that it doesn't influence the rest of the circuit too much.

Try 1uF at first, the ESP will have several tens of milliseconds to boot. If it doesn't work, try 10uF.

Answer 3

If you are a little tolerant of the 'reset' time, then just capacitively coupling the switch will work.

Ensure that the C you choose * 100k will keep the FET on for long enough for the ESPP to wake up and keep D1 low.

When the switch is (eventually) released, the new 'R' will reset the capacitor through the 100 kΩ. Successive retriggerings will be blocked for this time.