is it safe to power a NRF24L01 module from teensy 3.1/LC 3.3V pin?

Z

zasf

Member
I'm working on a project where my Teensy 3.1 board is a radio receiver.

Connections:
NRF24L01Teensy
VCC3v3
GNDGND
CE7
CSN8
CSK14
MOSI11
MISO12
IRQNC

CSK is not on standard pin 13, but using SPI.setCSK(14) I'm using pin 14 and thus I can save the onboard led.

Teensy 3.1 should provide max 100mA on 3.3V pin and NRF24L01 should consume max 13.5mA so well below the range. I'm asking because I had my transmitter and receiver well set, working as expected, I left both boards sending & receiving for a couple of hours just to check that everything was allright.

Later I further developed my code and I was changing some features (reducing the payload size), when after several uploads, my Teensy 3.1 stopped working. It was not receiving anymore and the board became unrecognized by macos. I switched to my Teensy LC board, as they have the same pinout, exact same problem.

At first I thought I had burnt both of them, but how? NRF24L01 current absorption should be far less than what teensy 3.1 and LC can provide. Later on I discovered the teensy not recognized by teensy loader page and resolved by connecting the boards with reset button pressed.

So back to the question, is it safe to power NRF24L01 module from teensy 3.1 3.3V pin?
What about using a teensy LC board?
 
For "production" usage, I personally never power anything from the onboard regulator regardless of the power consumption by devices. However if I'm prototyping stuff on a solderless breadboard, I'll use the onboard regulator for devices.
 
Used a NRF24L01 module several times with a Teensy 3.2.
Powering the module from the 3V3 Teensy output pin never gave an issue.
However, I did use a 10uF + 100nF decoupling capacitor near the NRF24L01 module.
I don't expect a problem with using a Teensy LC.

Paul
 
I took some time and arranged a simple setup with Teensy31 receiving and TeensyLC sending, using the simplest rx/tx sketch taken from the walkthrough, it worked. Then I tested all my nRF24L01 modules and they all work. I'm very happy that my Teensy31 and Teensy LC are back to business.

By doing so I realized that the problem was not on the receiving side of my project but on the sending side. For sending I use a Attiny85 with the RF24 3 pins configuration. The attiny85 kept resetting when the incident in post #1 happened, I noticed that but I believed it was some sort of problems with "interferences" from the Teensy31 receiving. I believed that because Attiny85 sending unit was working fine untill I switched on the Teensy31 receiving. I had the tiny working on 3v3 voltage with 1A power supply but somehow sending the first message triggered the problem and caused the unit to reboot.

Now the tiny is on 5v voltage, same power supplier, nRF24L01 voltage is lowered to 3v3 with a red LED. Everything is working fine as before. I'm using Teensy31 as receiver but I tried on TeensyLC and it works fine as well.

What I don't understand is why the tiny failed to work on 3v3 after "some time", when it worked fine for a couple of hours. I would like it to work on 3v because I plan to power it with a battery.

Thank you
 
zasf said:
I would like it to work on 3v because I plan to power it with a battery.
Click to expand...

If you have the available space in your project, you might take a look at the <Adafruit PowerBoost> line of projects. All models convert from LIPO battery input levels to 5.2VDC output levels, and some models add the ability to manage/charge the batteries as well. I have used the <PowerBoost 1000C> successfully in several of my long-running projects.

Good luck & have fun !!

Mark J Culross
KD5RXT

P.S. I am not connected to Adafruit in any way, except the following: I send them money, & they send me stuff. I am simply a satisfied customer sharing my specific positive experiences with some of their products. MJC
 
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Or you could consider something like this.Battery based power bank with 5V and 3.3V output and battery charging/management.
aaa.png
 
Thank you for your feedbacks.

I spent some more time on the project and finally realized what was the problem. The "red LED" was providing less than 1 volt. This is why the tx slowly stopped working. It was not a sudden death of the LED, but slow decay which created a lot of confusion: Attiny85 failing to work under 3v3, sometimes sending sometimes not.

It was an old red LED, removed from the pcb of a another project and I was happy had found it a new life. Now I understand it's better to use a proper voltage regulator with capacitors.

I will buy some regulators in order to have some spare in case of future needs :)
 
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