ATMega 328, nRF24L01 and power issues

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Hi, I am using a RF radio nRF24L01 with a ATmega328 and the RF24 library. I have an issue where when the ATMega328 runs off of battery power 6.0v or via a buck converter (5.7v) the radio does not work (does not send or receive). When I connect power via a USB RS232RL, the radio works. The power to the radio supplied by the USB is 4.7v. So I am leaning towards a power issue. So I connected the battery source with a potentiometer connected to the Radio and reduced the voltage to 4.8v and the radio does not work.

 

All the other functions work when powered by the buck converter, battery and USB RS232TL. For example, I have 2 GP2Y0A21YK0F Sharp IR Analog Distance Sensors connected and they work.

 

Any ideas as to what could cause this issue? I understand I have not posted any schematic at this point, but I was looking for some help to point me in the right direction.

 

Thanks.

This topic has a solution.

"When all else fails, read the directions"

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Um, How many volts are you powering the NRF24L01+ with? It's IO pins can tolerate 5v, but it needs 3v power.

274,207,281-1 The largest known Mersenne Prime

Measure twice, cry, go back to the hardware store

Last Edited: Sat. Nov 15, 2014 - 02:34 AM
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When under USB power (RS232) 4.9v. This works.

 

When under other power source, around 5.1v. When I mix some old batteries in with new ones, I can get about 4.8v and it works. Since I am horrible at electronics (trying to learn). How is the best way to achieve the target voltage 4.8v from a source of 6v?

"When all else fails, read the directions"

Last Edited: Sat. Nov 15, 2014 - 01:04 PM
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You are operating the nRF24L01 outside its manufacturer's specification. It is a miracle that it hasn't died and burned your money.

 

Ross McKenzie ValuSoft Melbourne Australia

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I see :( - So how can supply the 328p with 5v (needed to the sensors) and run the RF at 3v?

"When all else fails, read the directions"

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By using a 3V3 LDO regulator between the 328's 5 volt supply and the nRF24L01 supply rail.

 

Ross McKenzie ValuSoft Melbourne Australia

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PhillyNJ wrote:

I see :( - So how can supply the 328p with 5v (needed to the sensors) and run the RF at 3v?

 

Or if you don't have a LDO handy, a couple of diodes in series (cheap 1n4148's will do) or a red LED to drop the voltage.

I find these red LEDs work great for dropping 5V to 3.3, and double as a power/activity LED at the same time:

http://www.dipmicro.com/store/BR...

 

I have no special talents.  I am only passionately curious. - Albert Einstein

 

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Ok, I picked up a LM327T Adjustable Voltage Regulator at my local electronics shop.

 

According to the datasheet:

 

Vout = 1.25*(1+R2/R1)

 

R1 = 220 ohms (schematic shows 240)

R2 = 330 ohms

C1 = .1uF

C2 = 1uf

 

3.125v = 1.25*(1+330/220)

 

Connected the LM317 Vout to the RF and all works great. Thanks for the help!

 

LM317

"When all else fails, read the directions"

Last Edited: Sun. Nov 16, 2014 - 02:12 PM
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Glad it worked for you. I had fears that you may have damaged your transceiver by using 5 volts first time.

 

Ross McKenzie ValuSoft Melbourne Australia