USB Power Bank’s Auto-Off Becomes Useful Feature In Garage Door Remote

For devices that are destined for momentary and infrequent use as well as battery power, some kind of power saving is pretty much a required feature. For example, when [PJ Allen] turned two ESP8266-based NodeMCU development boards into a replacement wireless remote garage door opener, a handy USB power bank ended up serving as a bit of a cheat when migrating the remote away from the workbench. Instead of moving the board from USB to battery power and implementing some kind of sleep mode or auto-off, [PJ Allen] simply plugged in a USB power bank and let it do all the work.

This is how the feature works: some USB power banks turn themselves off unless they detect a meaningful current draw. That means that if the power bank is charging a phone, it stays on, but if it’s only lighting up a few LEDs, it’ll turn itself off. This feature can be a frustrating one, but [PJ Allen] realized that it could actually be useful for a device like his garage door remote. Turning on the power bank delivers 5 V to the NodeMCU board and allows it to work, but after about fifteen seconds, the power bank turns itself off. Sure, strapping a power bank to the remote makes the whole thing bigger than it needs to be, but it’s a pretty clever use of the minimum load as an effortless auto-off feature.

The NodeMCU boards in [PJ Allen]’s DIY remote use ESP-NOW for their wireless communications, a nifty connectionless protocol from Espressif that we’ve seen used in other projects as well, such as this ESP32-based walkie-talkie.

10 thoughts on “USB Power Bank’s Auto-Off Becomes Useful Feature In Garage Door Remote

  1. I have a 1100 lumin work light I use as a bike headlight. It has a USB port for charging, great. But it shuts off after running a LED taillight for a minute. Urgh! How much power load do I have to waste to keep the light on?

      1. Thanks jp314! This is useful info. Do you have any idea what the minimum current draw required for the pulses should be?

        I see a problem where a 555 really *IS* the best solution….

    1. i just went oldskool and popped a small (5AH) Sealed Lead Acid on my bike lights; when compared to a pre-made or roll-your-own Lithium pack, the balance was a no-brainer

      The premade lithium packs use a custom (12.6v) charger
      SLA uses any car charger

      BMS safeties at 5A draw (my horn made it shut down)
      SLA gives no fucks

      I did not want to go through the whole song-and-dance of spinning up a battery pack from cells (this was before I had a 3D printer)
      SLA 5AH, ‘home alarm system’ style from Big Box Hardware, $16 no-fuss

      yes, the lead acid weighs more, but that’s peanuts compared to the bike engine’s own weight

  2. I was accidentally reminded of this feature of power banks a couple of weeks ago. I have a remote ESP32 that monitors temperature. I have it running on a 6V lantern battery. The device sleeps most of the time, waking up every 20 minutes to report sensor readings. When that battery died and I was thinking about replacing it, I had the bright idea of using a USB power bank. I have a bunch of them here.

    I plugged in the ESP32, saw that it was sending readings and then going to sleep, and then I put it in the remote location. Updates stopped. Repeat that 2 or 3 times with different USB power packs and other ideas. About then I remembered about this automatic shutdown feature. Doh! All of my USB power packs seem to have that feature.

    The ESP32 is back to running on a 6V lantern battery (actually, 2 that I wired in parallel for longer life).

    Very cool that someone was clever enough to exploit this feature for this interesting use.

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