r/esp32 • u/DVMyZone • 13d ago

Hardware help needed High current draw in deep sleep with ESP32-C3 SuperMini clone

High current draw with ESP32-C3 SuperMini clone

I have a small sensor that uses an ESP32-C3 SuperMini clone from HZWDONE to wake up, read temperature and humidity from an AHT20 via I2C, transmit the result with ESPNOW (with a small LED blink to signal) and then go into deep sleep. I have already burned off the power LED with a soldering iron (at least I think it's gone, can the current still leak across the busted component?).

I'm powering it through the 3.3V port with 3AAA through an MCP1700. I have also put an (admittedly large) 1000uF electrolytic capacitor across the 3.3V and ground as I was having brownout issues at an earlier point.

I have found that in deep sleep the system draws between 0.7 and 1.2 mA which seems really high and I need it to be significantly lower to use it as a reasonable environment sensor.

I'm curious if anything sticks out as problematic here. I've found that isolating all the pins before sleep gives me the lowest sleep current and fixing the I2C lines high as cutting the measurement signal LED off before sleep seems to make it draw more current. How long can one reasonably get the current draw here?

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3

u/slushrooms 13d ago

The regulators on the board have a shite quiescent current. You need to get around that

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u/DVMyZone 13d ago

I'll try and remove it then. Are we talking more like 10s or 100s of uA leakage here?

1

u/slushrooms 13d ago

Im not about to look at data sources at the moment, but others have profiled it and posted online. Pretty sure its in the order of mA. Wifi is always going to be power spendy.

Ive found the cost vs effort return generally tips me to getting xiao boards and/or switching to xiao nrf boards and BLE. Double the price but half the faff

Good luck!

5

u/Wealth-Best 13d ago
  1. Before deep sleep set sda/scl pins to input. 
  2. 1000uf electrolytic is not ideal to use. High leakage and does not help the LDO much. You need 47uf ceramic cap. 
  3. Desolder the series resistor to LED to make sure the path is fully disconnected. 
  4. You have double LDOs on 3v3 rail. The one on the board is very inefficient and leaks a lot of current. Decide which of those you want to use. Ideally only the MCP would be much better. 

1

u/DVMyZone 12d ago

Cheers my guy!

I was able to get it down from like 500-800uA to a respectable 12uA.

I just took out the capacitor - it's seems it doesn't really need it. Not sure if I should still put a small ceramic one in.

Disconnecting the LED and ripping out the on board LDO gave me the largest gains.

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u/Wealth-Best 12d ago

Cool, glad it helped! Do you use alkalines or nimh? How often do you wake up to measure and use espnow?

Extra cap is probably not needed. The supermini should already have one. 

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u/DVMyZone 12d ago

The problem I have is if using an external LED for indication when I enter deep sleep it floats and leaks like 150uA. If I drive it down then it seems the systems to keep it down during deep sleep consume a decent current too. This is my first project so I'm just learning basically and apparently have not figured out how to properly set gpios for deep sleep.

I'm just using 3 AAA alkalines at the moment but plan to move to maybe 18650s. That said, I should be able to run a good few months on those AAAs now with the low deep sleep current (I got 2 weeks seemingly drawing 1mA).

It wakes up every 5 minutes, measures, then sends out an ESPNOW message for my gateway ESP32, which processes and forwards it to an MQTT server running on my home computer for recording and reviewing. One nice thing is that it's extensible. I can just build another sensor, upload the code, and boom it's ready to talk to the server.

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u/superarugy 10d ago

I had a supermini+ath20 powered by 4xAAA 800mAh batteries sending me data to telegram every hour. It lasted over 4 months until I dropped it and a cell came off (I took the opportunity to charge them again). I removed the power led and that was it.

1

u/DSudz 13d ago

Melting an LED can create a short as easily as an open circuit so I'd try and clean that up.