Does the amount of farads matter for nRF24L01+ pa

I have seen some people solder 55uF and 35uF on their radios. But most people suggest a range, I think it was 4.7-100uF?

Anyway, I am willing to try, but out of curiosity, does it matter? I think no because it is like a battery -- the load will take what it needs, but I don't know

Also, which is + on a decoupling cap? Is it the one with the white dashes?

There probably is an ideal value (or one that is at a sweet spot of solving the problem at minimum cost/bulk), but I don't know what it is.

The issue is that while the NRF24 modules available online have the small decoupling caps (~0.1uF) on the board, they are designed for being connected to a really solid power rail - not one on the other end of longish wires with mediocre connections, so the same effect as decoupling caps are normally needed for happens on a slightly larger/longer scale when the current use suddenly spikes when it transmits. The symptom of this is that (particularly at max tx power) the NRF24 module sometimes freezes when you try to transmit with it.

The 4.7~100uF range is a good default range to pick a cap from for this sort of application - and my impression from reading discussions of this issue is that just about anything in that range is effective under typical conditions I would pick a ceramic cap, not an electrolytic, given the choice.

Regardless of what purpose the cap is used for (decoupling capacitor is a role, not a type of capacitor), the + side of the capacitor goes to the side that will have the more positive voltage on it. I don't know what sort of cap you have in mind, so I can't confidently tell you which side is positive or negative (on electrolytics, there's normally a white line on the negative side, with a - sign on it).

Hi,
More info about power for nRF24L01 HERE: http://arduino-info.wikispaces.com/Nrf24L01-2.4GHz-HowTo

I have tried lots of variations on this theme over the past 5 years or so. I used to use 22 uF tantalum capacitors which were physically small and seemed to work pretty well.

But there are TWO usual problems when nRF24L01 based devices don't work:

  • Bypassing close to the device (as mentioned above)
  • 3.3V supply current capability. The Arduino UNO and MEGA do not have enough 3.3V power to run the high-power modules. So you either need a separate 3.3V supply, or a good 5V to 3.3V regulator.

There is one good solution for all of these issues for about $1.50 each: the nRF24L01-specific 'breakout board" or "Base Module" like these:

This has the 5.0 to 3.3 V regulator, good bypassing capacitors and easy to connect labelled pins.

I never use anything else now.

DISCLAIMER: Mentioned stuff from my own shop... where, of course, I also sell this stuff!
HERE

I have some LM1117 3v3 regulators sitting in my Robotics lab at school and since I asked if the amount of F matters, can i just run around the class, pick two caps and put it in a circuit with the regs?

The datasheet for those says that two caps must be used -- it says one 0.1uF and the other 10uF. But are tjose values saying I need at least those values? Like in order for the regs to work, I need caps that exceed those vals?

Choosing capacitors is different from something like choosing resistors, in which case crossing on with higher ohms will weaken your volts, I assume.

JeromeAriola:
I have some LM1117 3v3 regulators sitting in my Robotics lab at school and since I asked if the amount of F matters, can i just run around the class, pick two caps and put it in a circuit with the regs?

The datasheet for those says that two caps must be used -- it says one 0.1uF and the other 10uF. But are tjose values saying I need at least those values? Like in order for the regs to work, I need caps that exceed those vals?

Choosing capacitors is different from something like choosing resistors, in which case crossing on with higher ohms will weaken your volts, I assume.

Regulators are picky about the specifics of the cap used - I'd never just seat-of-the-pants' it like one typically does for picking caps for extra power supply filtering; the 1117 regs, which are made by everyone with a semiconductor foundry, while pin-compatible, do NOT have the same requirements for external caps (surprisingly)

The datasheet I am looking at for the Texas Instruments LM1117 specs a 10uF tant on the input and output; while their app notes show 10uF tant on input, and often a 100uF electrolytic on the output, and they have a minimum ESR spec on the output cap (so you can't use cheap abundant non explosive (tants have a - somewhat undeserved - reputation for exploding) ceramic caps).

On the other hand, the ZLDO1117 (From Diodes Inc - also the best of the 1117 regs) wants 4.7uF ceramic or tant on the output and input.

Some only spec a 0.1 on input (though you should put a larger one in parallel with that if wires from the power supply to the regulator are long)

Different regulators have different requirements, and they are often rather picky - those values are necessary to meet the specs in the datasheet - depending on the regulator and how inappropriate the caps are, incorrect caps can either result in worse transient response, more noise, or the output voltage oscillating. The capacitance requirement is a minimum (within reason), but the capacitor type (or ESR) requirement is no joke.

Is there a safe range for the amount of farads that you would suggest because.I am not sure where I got mine. Straight outta eBay

JeromeAriola:
Is there a safe range for the amount of farads that you would suggest because.I am not sure where I got mine. Straight outta eBay

For a regulator? I'd try to determine what model it is from the markings (and ebay listing), pull the datasheet, and use what it recommends. IIRC 10uF tantalum cap is okay for all the 1117s. But if possible, I'd try to skip the tant by determining what regulator it was.