Pi Pico Power

Update on 17th November 2021: having now played with an ESP32-S2 based board, I should say that it draws a lot less power than the combo described here.

Power Measurements

I was thinking about using a Raspberry Pi with an ESP32 based Wireless Pack for a battery-powered monitor, so I was interested to see how much current it draws.

All the tests below use Adafruit’s Circuit Python. Normal operation is what the name suggests, and includes time sleeping with the time.sleep() call.

Light sleep uses the alarm.light_sleep_until_alarms() call; deep sleep uses the alarm.exit_and_deep_sleep_until_alarms() call.

Pico only

The first tests use only the Pico board, powered at 5V through the USB port.

State	Current draw / mA	Power consumption / mW
Normal operation	18	90
Light sleep	12	60
Deep sleep	5	25

Accuracy for the current measurement is about ±0.5mA. There’s a bit of high-frequency noise, presumably from the DC-DC converter, but the very little variation otherwise.

Pico and Wireless Pack

The second set of tests use the Pico board with a Pimoroni Wireless Pack¹, all powered at 5V through the USB port.

State	Current draw / mA	Power consumption / mW
WiFi not in use	36	180
WiFi in use	91	455
Light sleep	29	145
Deep sleep	22	110

As can be seen just plugging in the Wireless pack increases the current consumption by about 17mA. Thus if the Pico is running normal code the current consumption is roughly doubled if it’s sleeping it more than quadruples. It is rather a shame that the sleep current is so high.

If you actually use the WiFi consumption rises sharply: nearly three times higher. I have no idea if the current will change in different settings: in my test the ESP32 was about a metre away from the WiFi Access Point, so presumably very little RF power was needed. The single number above hides significant variation when the WiFi is active.

Pico, Wireless Pack, 12V supply

I used a Pololu D24V10F5² buck converter to drop 12V to 5V, and then supplied that to the Pico. Internally it uses the Intersil ISL85410 DC-DC converter.

State	Current draw / mA	Power consumption / mW	Efficiency
WiFi not in use	16.5	198	91%
WiFi in use	40.5	486	94%
Light sleep	13.5	162	90%
Deep sleep	10	120	92%

Conclusions

I learned a couple of things:

• The Pico Wireless Pack draws a lot of current, even when it’s not doing anything.

• The Pololu buck converter really does deliver 90% efficiency in a real application.

So one disappointment and one nice surprise!

Update: If you care about low-power, it is probably more sensible to use a pure ESP32 design.

Written by Martin Oldfield on 16 Nov 2021.
Contact: Martin Oldfield, ex-atelier@mjoldfield.com
This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.