NRF24L01 Tx Failed many times then ok

Hi,

I am experimenting more with the NRF24L01, trying the swapping roles example.

This always gives tx failed 5-10 times before a successful tx and reply is generated, not sure what could be wrong...

I have one UNO and one MEGA approx 5m apart with 10cm coiled wire as antenna's.

This Simple nRF24L01+ Tutorial may help. I hope the examples are more straightforward.

I am curious about your antenna. Can you post a photo.

I only have the nRF24s with the PCB antenna. They work very reliably at a much longer range than 5m. I tested them at 110m outdoors.

...R

Hi,

Thanks, see attached images.

More pics…

Image from Replies #2 and #3 so we don’t have to download it. See this Image Guide

cad2d81f23449fcc3c156f087102eae007a74890.jpg

9ad1b426aa605fc35d364b0724c612c670868383.jpg

…R

Have a look at the length of the PCB antenna. I have a suspicion it is the correct length for a 2.4GHz wireless signal.

This is a photo of the nRF24s that I have been using. I’m not sure why the antennas are different, or whether there are any other differences. My devices have the nRF24L01+ version of the Nordic IC.

The other chip in the picture is an Attiny1634

DSCF4484small.png

…R

OK, I just tried triming the arial length to match the tracking length on your pic, I now get better results, only failing 2-3 times before going through. Is this normal?

I have a couple of thses on teh way, hopefully they work better.

http://www.ebay.com.au/itm/262640607586?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

dudester:
I have a couple of thses on teh way, hopefully they work better.

If you solder crazy 'antennas' to them they will probably fail like the old ones.

Do not mess with the PCB-antenna modules.

dudester:
OK, I just tried triming the arial length to match the tracking length on your pic

Just take your antenna off completely and put it in the trash.

...R

Someone spent quite a while with a 2 or 3d simulation package - eg Sonnet - designing that PCB antenna , and measured impedances on test with a vector network analyser - costing many thousands of pounds - to check it was OK.

You won’t improve on it with a random bit of wire

regards
Allan

Robin2:
Just take your antenna off completely and put it in the trash.

...R

When I first purchased these I ran them with no arial and could not gert any comms at all.
I just tried again removing the arial and do NOT get any successful transmissions now.

The reason I put the arial there is because I read that this particular pcb didnt have an onboard arial.

The strip of trace sort of shaped like a J is the antenna. That's how short it needs to be for the frequency used, 2.4 GHz.
Longer wire, such as 17cm for a 433MHz Tx and Rx module, are added. Not so for 2.4 GHz.
Found by googling:
"velocity = frequency * wavelength

In this case the velocity is C, at say 300,000,000 metres per second. The frequency is 2.4GHz, or 2,400,000,000 Hertz. Dividing the first big number by the second yields a wavelength of 0.125 metres, or 12.5cm. Since we're using quarter-wave antennae, that works out at just over 31mm."

If you carefully measure the J shape on the PCB, I bet you will find it is about 31mm.

Look at Figure 34, page 68 here.

dudester:
When I first purchased these I ran them with no arial and could not gert any comms at all.
I just tried again removing the arial and do NOT get any successful transmissions now.

Do you know if your module has an nRF24L01 or an nRF24L01+ chip on it. They are different and it may be that a library for the current nRF24L01+ will not work with the obsolete nRF24L01.

If you have the older version you should get the two Nordic datasheets and compare them and see if the library you are using is suitable.

As far as I can see the pinouts on your module are also different from mine.

Do you have a 10µF capacitor across Vcc and GND close to the module?

Maybe the simplest thing (since they are cheap) is to get a pair of modules like the ones I am using.

...R

Definitely has the + chip, marking is there.
Can't see a 10uf cap but they are all set so hard to tell...

Will order same modules you have and give that a try.

. Since we're using quarter-wave antennae, that works out at just over 31mm."

Only in free air... on FR4 it'll be about 2/3 that.

regards

Allan

dudester:
Can't see a 10uf cap but they are all set so hard to tell...

You must supply that.

...R

allanhurst:
Only in free air... on FR4 it'll be about 2/3 that.

Sounds like you may know the answer to something I have been wondering about recently.

I have other 2.4GHz transceivers that have a short piece of flexible wire for the antenna.

I wonder if I cut through the antenna track on the nRF24 PCB and soldered on a short piece of wire (31mm ?) would it work as an antenna?

The reason I ask is because it would be a means to get the antenna outside a metal enclosure (on a model train).

...R

Robin2:
You must supply that.

...R

Sorry, not sure what you mean by that?
They are all surface mount caps so cant tell their values.
I am I suposed to add a cap to the pcb?

dudester:
Sorry, not sure what you mean by that?
They are all surface mount caps so cant tell their values.
I am I suposed to add a cap to the pcb?

Of course not.

Put it across the Vcc and GND pins of the module, or very close to them. Just a regular 10µF electrolytic capacitor.

The red arrow in this image shows where it is on a project that I built.

ModelTrainDSCF4238partA.png

…R