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nRF24L01 Module will only work when connected to computer via USB

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(@jettedlikeshek)
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Joined: 1 month ago
Posts: 16
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@zander Yes, I believe it's just the transmitter. When I use the computer USB connected to the transmitter everything works great. But with my luck I'm guessing when I try it again the receiver won't work this time, but we will have to see. 

I think I am going to try my luck with power banks using AA or 9V. I'm not sure if the 18650's are in my budget especially with the charger. I'm already a little bit over the set budget for this project. I only need the batteries to last maybe 15 minutes as I can swap them out for new ones after each round of our competition.

I appreciate your help, electronics and circuits are by far my least knowledgeable topic and I am definitely going to be working on this over the summer and in my future courses. 


   
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(@jettedlikeshek)
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@zander This makes sense, I have also seen a ton of people agreeing with you about the number of knockoffs there are out there.


   
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Ron
 Ron
(@zander)
Father of a miniature Wookie
Joined: 4 years ago
Posts: 7140
 

@jettedlikeshek Ok, sounds like you have the situation under control. The car/receiver is good, the transmitter needs it's own 5VDC power not connected to the NANO, and the NANO can probably work just fine with a single 9V battery on VIN.

NOTE: You could also try first connecting the adapter 5VDC to the NANO +5VDC (pin 27 is output as well) and then use either 2 9V batteries or some other battery arrangement with more life in it.

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
My personal scorecard is now 1 PC hardware fix (circa 1982), 1 open source fix (at age 82), and 2 zero day bugs in a major OS.


   
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Ron
 Ron
(@zander)
Father of a miniature Wookie
Joined: 4 years ago
Posts: 7140
 

@jettedlikeshek YEP, learned the hard way and recently scrapped a bunch of fakes. I found a reliable source now but shipping is looooong, like in June.

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
My personal scorecard is now 1 PC hardware fix (circa 1982), 1 open source fix (at age 82), and 2 zero day bugs in a major OS.


   
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(@jettedlikeshek)
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Joined: 1 month ago
Posts: 16
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@zander Yes this sounds like a plan. Thank you again for your help!


   
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(@davee)
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Joined: 3 years ago
Posts: 1725
 

Hi @jettedlikeshek,

RE: I am confused as to why this wouldn't be sufficient for the nRf24L01 adapter module. If the LDO regulator takes the 9V down to 5V and provides a steady 5V continuously, why wouldn't it provide a constant 5V to the adapter module as well?

With electricity, you need to consider both voltage (measured in volts) and current (measured in Amps).

For a simple analogy, consider a water flow through pipes and nozzles. The voltage is similar to the pressure of the water, the current is similar to amount of water flowing.

And to complete this picture, electrical power, which is measured in Watts, is product of the voltage and the current for direct current. (Alternating current power is a bit more tricky to calculate, although the principle is the same.)

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From your comment "Based on the Arduino nano datasheet...", I assume you have a 5V Nano.

This effectively has two voltage regulators, but the amount of current that they can supply is limited. The first one, regulates a voltage fed to the Vin pin, in the range 7V-12V down to 5V, and the second is built into FT232RL chip, regulates 5V down to 3.3V.

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In a previous comment, you said that the NRF24L01 worked when power was supplied by USB, but not when power was supplied from the 9V battery. If this is still the case, then I suggest this is because the 7V-12V to 5V regulator cannot supply enough current for both the Nano processor and the NRF24L01 at the same time, and it is protecting itself, by limiting the current flow. This behaviour is mentioned by Bill in his blog. 

I suspect the 9V battery can manage, but its lifetime may be rather short. Check its voltage with a meter. A new alkaline battery will be around 9.5V with no load. If it is below 9V, then it may already be getting exhausted.

5 x AA alkaline cells in series, producing 7.5-8V will last a lot longer than the tiny 9V alkaline batteries, and maybe easier than rechargeables, etc, if you just need to demonstrate a system working for a short time.

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So you need a separate regulator for the NRFL01. (Use Nano 5V for the joysticks). This could be a linear regulator, of which many are available as 3-pin devices, albeit read the data sheet to find out what capacitors are advised. Alternately, you could try of the small buck regulators that are cheaply available on small PCBs, such as the one based on LM2596, as Ron suggested, or you may find a smaller board based on a different chip. Ensure it can provide at least 1A at 5V, and also add a capacitor of about 100 microFarad to the output.

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Best wishes and good luck, Dave


   
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