ESP32 Forum

I'm looking for a lowest battery consumption, and the battery size not very heavy.
With ESP32-CAM in deep sleep mode I have 4mA current draw. The battery capacity is 1500mA. This configuration will run maximum 15 days.
Now I tested a PIR sensor SR-602. It takes only 1uA or 0.001mA! The lowest battery consumption I have ever seen. Only this sensor will work about 62500 days from 1500mA battery.

Now the wanted scenario: In the idle time, only PIR sensor is powered on. It waits for the event. When the PIR sensor triggers, it powers on the ESP32-CAM. ESP32-CAM takes a picture, save it on the memory card and cut off the power so only the PIR sensor remains active. I need a external circuit to do this.

The SR-602 sensor output signal is 3.3v for only about 2.4 seconds (not modifiable). If I use a transistor like a switch, the ESP32-CAM will be powered on for only 2.4 seconds. How to increase this time? Even when the PIR signal will fall from high to low, I need to maintain the ESP board powered on to finish the task, then cut off the power.

Any ideas will be apreciated

You probably want some kind of latching circuit (like an S-R flipflop) where the PIR turns the ESP-CAM on and a GPIO on the ESP-CAM can turn it off.

I could test it if I have a schematic of this latching circuit. Thanks

This is the one I use:
https://www.youtube.com/watch?v=Er8fSoeaZD0

Wow! This is the circuit I'm looking for. I will try it.
Thank you very much

I found using 2n7000 n-channel mosfets instead of the npn BJTs works better. You can get 100 2n7000 for less than $8 on Amazon.

I tested. The latch circuit is working fine.
Thanks