Is it possible to power an nrf24l01 from Attiny85's analog output pin?

Using Arduino Project Guidance
1

I am wondering if it is possible to power an nrf24l01 from one of Attiny85's analog output pins. I am thinking of the following setup for power:

CR2032 (3v) ---------> Attiny85(VCC)------>Attiny85(analog output pin)---> nrf24l01(VCC)

Hence when attiny is in deep sleep mode, nrf24l01 is also switched off. This should considerably reduce the power consumption.
Theoretically speaking, Attiny's analog output pin can output around 40mA and nrf24l01's power consumption is 11.3mA transmitting, 13.5 receiving.
Thank you for your comments.

2

I'd tend to use a P channel mosfet to switch the NRF24L01 module because you have also got to consider the capacitors on the module power rails and any additional ones you may need to add during any troubleshooting.
Here is a schematic: NRF24L01 Test with Arduino - Wiki

3

Thank you very much. I will try the P channel mosfet and revert.

4

First mistake.

Bad misunderstanding. 40 mA is the figure you must not approach!

Remember that at 3 V supply, the output pin effectively has a 40 Ohm resistor in series with it, so if you draw 11.3 mA, the output voltage drops to less than 2.6 V.

5

I totally agree with you in terms of power "dimensioning" for this case. Let me share what I did so far:
Trial 1) : powered nRF24 as :

CR2032 (3v) ---------> Attiny85(VCC)------>Attiny85(analog output pin)---> nrf24l01(VCC)

Result: it works fine. nrf24 sends data to a separate receiver (nrf24+esp8266)
Problem: after Attiny85 wakes up from deep sleep, nrf24 not sending data. I think this is more a programing issue. I will investigate it and revert.

Trial 2): powered nRF24 using P channel mosfet as suggested by 6v6gt (see attached picture)

attiny-mosfet
attiny-mosfet768×1024 202 KB

-Result: It works as well.
-Problem: same as with trial 1.
I will dig further and feed this post.

6

CR2032 is a very poor choice for the radio, but it will work for a short while.

7

The problem with the nrf24 after wakeup was solved. I including the nrf24 initialization after each Attiny85's wakeup.

8

Just for curiosity, I will check the lifetime of the CR2032 in the actual setup. I will even add a DHT11 sensor. Let's see...
oops. CR2032 cannot power a DHT11. It needs at least 3.5V :frowning:

9

That doesn't look right. Gate should go to the tiny pin and source to battery.

That was lucky!

11

Thanks for the remark. I corrected the picture.

attiny-mosfet
attiny-mosfet768×1024 202 KB

12

Still wrong!

13

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