Good day everyone! I'm at the verge of finishing a project but I'm a bit confused with something. In my project, this is the schematic I used for communication between two nrf24l01 modules:
After doing some research I found out that the range of my communication is a bit limited by the power supply of the arduino to the modules. So I found a better way to power the modules using a separate voltage regulator like this one:
My project uses a 7.4v 2cell lion battery. Is it better to connect the voltage regulator to the arduino nano 5v pin or to the lipo battery directly?
if you connect to the arduino 5V output pin, you are putting the Arduino's voltage regulator to work and then again go through your AMS1117 regulator.
You involve two not very efficient regulators (they dissipate excess energy as heat) and best would be to get a switching regulator directly connected to the battery (ensure you join the GNDs).
This may be part of the problem on the side with the NRF+PA, but it won't be the issue on the other side that has the 'bare' NRF module.
It won't make much of a difference. The power draw from the regulator will be momentary and last only a few milliseconds, and typically you're not sending data all the time. @J-M-L 's comment above make sense, of course, but the practical implications are limited. A (wasteful) linear regulator will work OK, and it will work to power just the NRF + PA module regardless of where you take its input from.
Again, this only applies to the side with the PA module. The NRF without the PA draws so little current that even the flimsy 3.3V output from a Nano will power it just fine.
PS: the whole range problem can be much more effectively solved by revising the antenna; you could use a small half-wave dipole antenna soldered directly to the NRF board while cutting the existing antenna traces. Alternatively, use an NRF module on both sides that has an external antenna instead of the little PCB-printed antenna. Improving the antenna will give a massive range boost while I doubt you'll see any real difference by changing the power supply situation from what it is now.
Your diagrams seem to show 7.4V Li-Po packs, and you used the term lipo in your post. These usually have over-discharge/over-current protection circuits built in.
But if you are using 2 Li-ion cells (for example 2x 18650 size cells), these usually don't have protection circuits, so you must provide them. If you don't, the cells can get damaged and when you recharge them, they can explode or catch fire.
In your circuits as shown, it doesn't make much difference. I would probably choose to connect it directly to the lipo, unless that was inconvenient for some reason.
As you have found, the 3V3 output from the Nano can only provide a few tens of milliamps, not enough for an RF transceiver.
With ams1117, as with all linear regulators, you will need to add capacitors to the input and output as shown in the datasheet.
If, once the power supply problem is sorted, you find the range is still not what you would like, there are other choices than nrf2401 modules with better range. For example HC-12 and LoRa. These types have lower bandwidth, but it seems to me you don't need a high bandwidth in your project.
EDIT: take care when choosing HC-12 modules. There are still modules around from batches that have a fault that severely reduces their range, and of course the sellers won't mention that. But the differences are easy to spot when you know how. If you can't tell for sure from the photos posted by the seller, buy elsewhere.
