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ESP32 deep sleep draws 8mA instead of 10uA?!?!

Posted by h4nk (8 posts) #1

Datasheet says about 10uA in deep sleep. I measure EIGHT MILLIAMPS. Battery lasted 9 days instead of the year I was bragging about!! esp_sleep_enable_timer_wakeup(600ULL * 1000000ULL); esp_deep_sleep_start(); It definitely sleeps, the wifi stops and current drops from 80mA. Board is one of those cheap devkits from the usual place. Am I missing some magic setting

12 replies

kris (16 posts) #2

You're measuring the board, not the chip. Those devkits have a USB-serial bridge, a linear regulator with a fat quiescent current, and a power LED. All of it stays on.

h4nk (8 posts) #3

The LED! ok I can desolder the LED

kris (16 posts) #4

That'll get you maybe 2mA back. CP2102 and the regulator are the rest. If you want the real number you need a bare module and a low Iq regulator.

dan_r (18 posts) #5

For what it's worth I gave up and used a bare WROOM-32 on a small carrier with an MCP1700. It's fine for a garage sensor.

h4nk (8 posts) #6

Parts came!! Bare module + MCP1700. Now reading 210uA. Better but not 10!!

kris (16 posts) #7

What else is on the rail? Sensor? Voltage divider for the battery?

h4nk (8 posts) #8

DHT22 and a divider, 10k + 10k for battery voltage. Oh no.

kris (16 posts) #9

There you go. A 20k divider on a 4V cell is 200uA all by itself. Go to 1M + 1M and put 100nF across the bottom resistor so the ADC has something to sample. And power the DHT from a GPIO, or a P-channel switch, so it's off during sleep.

zp_indirect (4 posts) #10

Also how are you measuring? A multimeter on the uA range has a big burden voltage. Can brown out at wake-up when it pulls 200mA through that range. If it reboots in a loop on the meter and not on the bench supply, that's why.

h4nk (8 posts) #11

GOT IT. 14uA with the 1M divider and DHT on a GPIO!!! kris you are a legend. Marking this solved. Burden voltage was also real, it kept resetting until I shorted the meter during wake.

kris (16 posts) #12

Nice. Post the numbers after a month on the battery, I'd like to see how close it gets to the sum.

sparrow (1 post) #13

Few weeks late, sorry. Anyone doing this on a newer part should look at the C3, deep sleep is about 5uA and the same board rules apply. Devkit numbers are meaningless, as above.

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