Comments on: EXTREME POWER SAVING (0µA) with Microcontroller External Wake Up: Latching Power Circuit https://randomnerdtutorials.com/power-saving-latching-circuit/ Learn ESP8266, ESP32, Arduino, and Raspberry Pi Tue, 18 Feb 2025 21:03:49 +0000 hourly 1 https://wordpress.org/?v=6.8.2 By: Riaz Ahmed https://randomnerdtutorials.com/power-saving-latching-circuit/#comment-1008993 Tue, 18 Feb 2025 21:03:49 +0000 https://randomnerdtutorials.com/?p=90119#comment-1008993 In reply to Sara Santos.

Hi. I have an xiao Esp32 C3 where the 5Vin pin is used to power an air quality sensor while 3v is used to power a pressure sensor. Due to 5v i have to supply battery power (stepped up from a 3.7v lipo) to use/5vin pin. Using the latch you so nicely described, will it be possible to modify the power source in your latch to 5V? What else need be changed?

]]> By: Grr https://randomnerdtutorials.com/power-saving-latching-circuit/#comment-961254 Wed, 25 Sep 2024 00:38:38 +0000 https://randomnerdtutorials.com/?p=90119#comment-961254 In reply to Rui Santos.

This would be fantastic!

]]> By: Patrick https://randomnerdtutorials.com/power-saving-latching-circuit/#comment-940026 Sun, 21 Jul 2024 06:48:06 +0000 https://randomnerdtutorials.com/?p=90119#comment-940026 I have a question about the reed switch application. Beginning from an open position, if the reed closes and stays closed then this circuit doesnt work because it’ll constantly be turning the power on. Therefore, in order to use a reed switch with this circuit you have to make sure that the reed switch only turns on momentarily. Is this correct?

]]> By: Lorenzo https://randomnerdtutorials.com/power-saving-latching-circuit/#comment-909070 Tue, 23 Apr 2024 20:00:48 +0000 https://randomnerdtutorials.com/?p=90119#comment-909070 suppose the trigger signal stays high; will the MCU be able to switch itself off in this case?

]]> By: Private https://randomnerdtutorials.com/power-saving-latching-circuit/#comment-869977 Sun, 05 Nov 2023 02:04:42 +0000 https://randomnerdtutorials.com/?p=90119#comment-869977 Hi, can u explain what to do if the push button should be able to switch everything off too (so not just through delay) ??? thank you

]]> By: Jake https://randomnerdtutorials.com/power-saving-latching-circuit/#comment-860270 Wed, 13 Sep 2023 11:56:14 +0000 https://randomnerdtutorials.com/?p=90119#comment-860270 In reply to DAVID HITCHINS.

Hi, I also have the same problem while trying to create a low power consumption door state detector using reed switches.
Have you tried this solution electronics.stackexchange.com/questions/519758/improving-edge-detector-with-latching-circuit-for-esp8266

]]> By: Stefan https://randomnerdtutorials.com/power-saving-latching-circuit/#comment-840175 Sun, 11 Jun 2023 13:35:53 +0000 https://randomnerdtutorials.com/?p=90119#comment-840175 Thanks for the tutorial. I’m trying to create a BOM for the PCB but have an issue with the list of resistors. According to the picture, in R6 you mounted a SMD resistor of value 2000 which should be 200 Ohm, but from the parts list the only remaining resistor that I cannot directly map using the SMD digit code ist a 220 Ohm resistor. Is it correct to assume, that one should use a 200 Ohm resistor at R6?

Once finished I’d be happy to send you my BOM to use with jlcpcb as I’m trying to get fully assembled circuits. But I’d also be happy if you’d upload a BOM in this article if you have one at hand.

Thanks.

]]> By: Stian https://randomnerdtutorials.com/power-saving-latching-circuit/#comment-773504 Fri, 05 Aug 2022 22:45:08 +0000 https://randomnerdtutorials.com/?p=90119#comment-773504 Hi and thank you,
I’ve gotten the latch circuit and example sketch to work be wiring up a push-button to power on the latch circuit pcb as described in the tutorial.
But now I’m trying to get a DS3231 from Adafruit to power on/trigger the latching circuit on an timed interval/alarm (every third day), and I’m completely lost.. It looks to me like the DS3231 triggers a low output when the alarm fires, so I don’t understand how to get the DS3231 to turn on the power..
Is this possible to solve or do somehow?

This is the ds3231 I’m trying to use:
https://learn.adafruit.com/adafruit-ds3231-precision-rtc-breakout

Would be forever grateful for any assistance!

]]> By: Justin Eltoft https://randomnerdtutorials.com/power-saving-latching-circuit/#comment-765745 Wed, 29 Jun 2022 18:44:44 +0000 https://randomnerdtutorials.com/?p=90119#comment-765745 Just put together a nodemcu (wifi disabled to save 60% of the power it uses) pcb with this on it, along with a pizeo buzzer, CR123A lithium, and reed switch for door open close detection. I expect it will get 1.25 years of battery life. Thanks so much for sharing! I used JLPCB!

]]> By: DAVID HITCHINS https://randomnerdtutorials.com/power-saving-latching-circuit/#comment-765151 Sun, 26 Jun 2022 23:35:59 +0000 https://randomnerdtutorials.com/?p=90119#comment-765151 In reply to Garry Keogh.

There must be something I don’t understand. When the magnet approaches the NO reed switch the circuit closes sending the triggering signal. But when the code has finished running and the latching circuit tries to switch off the power, there would still be a triggering signal (assuming it’s a door that is closed and stays that way for a certain long period of time) so the latching circuit would be triggered again … ad infinitum.
I read this other post https://randomnerdtutorials.com/latching-power-switch-circuit-auto-power-off-circuit-esp32-esp8266-arduino/ and I can’t see why the 2N3904 transistor would ever stop pulling the gate of the NDP6020P mosfet to ground and therefore why the latching circuit would ever stop supply power to the microcontroller. Can someone please explain my error here? Or maybe I am not wrong?

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