Quirky nRF24L01 voltage issues

Hi all,

I have this issue with an nRF24L01 module where I fail to understand the issue. After various attempts I hope someone here can maybe shed some light on the problem.

The Arduino I am using is the Pro Mini 5v. So, somehow I need to get 3.3v as the VCC of the nRF24L01 module needs that.

I have tried various options, none work - but one. In that case printDetails() of the RF24 library will actually say something meaningful). And that one is rather strange...

Electronics are not really per se my thing, I just like to tinker with it and learn on the go. So maybe I am missing a detail.

NOT working:

  1. Making a voltage divider using a 2700 and 5600 resistor. According to Voltage Dividers - learn.sparkfun.com this will return into 3.36 volt. My voltmeter agrees.

  2. The same setup, but adding a capacitor between the VCC/GND going to the module

  3. Using 4x 1.2AA NIMH batteries to power the entire Arduino (leaving the FTDI VCC/GND disconnected) on the RAW and GND pin. Making the voltage divider from these bateries.. Still 0x00

  4. Using 2x 1.2 AA NIMH batteries (giving about 2.9v, freshly charged) directly to power the module (with and without capacitors), and the Arduino from FTDI.

Working:

  1. Powering the Arduino from FTDI (or battery) and the nRF24L01 module from a Raspberry Pi 3.3v VCC/GND (As I had another module working on this, I want to communicate between RPI/Arduino)

I am rather clueless why powering from the RPI works and not from the batteries for example. The module should function at 2.9v. Also why the other configurations do not work are also strange to me.

Any suggestions? I have eBay'ed some voltage regulators, yet I am really curious why this does not work as it has been bothering me for many hours in the last evenings...

Thanks for any suggestions :slight_smile:

This is my fairly uneducated guess but:

Voltage dividers are good for voltage references but not so much for power supply.
I read that the output voltage varies with load and that you waste allot of power.

Measure the voltage your getting to your device when its connected and powered as apposed to the no load measurement you have probably been taking from the voltage divider.

Also be sure your taking your voltage to your device from the right points in the divider, if you see 3.3 volts on one side you will see 1.7 on the other.

I suspect its a voltage issue and that it is that your divider cannot maintain the voltage at the current you require or that you are using the wrong side of the divider and are undersupplying the voltage to the device. Either way test voltage with the device connected to be sure.

I think your better of with a 3.3v linear voltage regulator, they will supply you a clean and stable 3.3 v.

Hi!

Thanks for your reply. I also did notice that the voltage divider behaves a bit 'weird' (lower voltages, quite a bit) when there is load on it. Fortunately, today my voltage regulators came in. So I just gave it a try (with 4x AA): Nothing

Hooked up the RPI again as a test, and it worked.

So, then I decided it might be wise toconnect the grounds of the GND out of the regulator and the GND of the Arduino Pro Mini.. and it finally started to give a proper status signal! So That was very likely the reason. I am just not always so comfortable connecting different grounds together, because it seems rather "odd" to me. The path of an electron is sometimes a mystery for me :blush:

Oh no!! That ones got me before too, Yes almost always need grounds connected!!!
Oh man I bet you slapped your forehead when you realised!
Cool though sounds like that problems solved. Its usually pretty safe to connect grounds, its usually important.

If you have two arduinos connected to usb which will talk to each other and then put one of them on batteries they may stop talking. Because the grounds were being shared through your computer via USB

I have only come up agains a couple of times where I couldn't bring grounds together, and they were when needing to maintain isolation between two sides of a DC DC step down.

Actually its a good question.... Can anyone suggest reasons when you could not bring grounds together? Id like to know more about these situations, cause I kinda work on the idea that its almost always ok and if its not the case I should know!

Hello,

I will write my experience,

You can use a resistor divider but you will get only the voltage correct, but the current it will not enough ...

Another quick solution it is to use 2 diodes (1N4148) from 5V, it will works but not with the Max power of nrf24l01.

The win solution is to use L78L33ACZ 78L33 + 3.3V Voltage Regulator IC , it is not expensive and you can use the Max power :wink:

Good luck :slight_smile:

Hi all,

Things went quite well so far :). It is a national holiday, everything closed and the weather is rather sad. Perfect for tinkering with Arduino and RPI :slight_smile:

I managed to get nanopb (protobuffers) working on both Arduino and RPI, and they can happily exchange data. The Arduino will sent sensor info from a DHT11. The RPI will sent some random values as test. The Arduino does stuff with the interrupt pin of the nRF24L01. I plan on writing a bit about my experiences later on, to help others getting started.

Now, there is only one issue: power consumption. I have been testing a bit, and using the RocketScream library I can get to 27 ma with everything attached. Removing the radio makes it go down to 12 ma. And then there is this big gap between 12 and 0.06 all caused by the linear voltage regulator I use (http://www.ebay.co.uk/itm/1PC-New-DC-DC-4-5V-7V-to-3-3V-AMS1117-3-3V-Power-Supply-Module-Voltage-Regulator-/301123756227?ssPageName=ADME:L:OC:NL:3160). I checked the datasheet of the chip used (AMS1117) and it is about correct.

Now I was thinking.. What if I put the entire circuit of the regulator behind a transistor and occasionally turn it on when transmitting data? That should work right?

Or did anyone else have solutions to reduce the power consumption. I would like to power the device with some batteries, so 27ma is quite much :). I could not find so much information regarding the nRF24L01 and this.

Thanks again for any suggestion :slight_smile:

Edit: Oops, overlooked tasosstr's reply. I will look at that voltage regulator and see how much mA it consumes :slight_smile:

You can also obtain regulators with an Enable pin, and just turn it off directly.
Take any control pins to follow-on circuits low first so they are not phantom powered from high signals bleeding thru input protection diodes.
Example: LP3985

Selection depends on how much output current is needed.