I can not really find an answer to this question. Perhaps here are people who know it.
I have following step down regulators:
And I want to power Arduino Pro Mini in 5v version from it. Connecting directly to vcc not really works. All other things work, but my rf24l01 is not working if I do so. If I connect to RAW all works correct. But I am afraid if i damage something if I do so for longer time, because I thought the voltage regulator needs higher volt.
From the tech specs I don't really get answer to this:
"Board Power Supply 3.35 -12 V (3.3V model) or 5 - 12 V (5V model)"
From this it seems to be ok to power with 5v. But perhaps they are talking about the vcc pin and not raw?
Maybe your step-down regulator is generating a lot of noise, try a filter, maybe a 4R7 resistor in conjunction with a 470uF capacitor, it would be better to use inductor.
The regulator of the mini pro card is very little powerful, I think it only serves to feed itself, nothing additional.
I think it's cool that you want to know what the reference of the information is,
You can follow these steps:
1- First find the electronic schematic of your board, and then
2- Find the controller model your board uses; this should be described in the diagram.
3- Then look for the controller datasheet.
4- In the datasheet should be described the operating condition, such as power dissipation, this is very important, even if the maximum allowed voltage is higher, if it is a linear regulator, the energy dissipated counts a lot.
RAW requires 7v minimum (well, maybe 6.5) to get 5v on the output, as that's the input to the regulator.
If supplying with external 5v, you need to connect it directly to Vcc.
The NRF24 is a 3.3v device. powering it with 5v may damage it. If you want to use it without level shifting, you should use a 3.3v pro mini (and a 3.3v serial adapter - the power line of the serial adapter is connected directly to the power rail, so a 5v serial adapter on a 3.3v pro mini will result in the pro mini running at 5v)
It may be that what's happening is that when you get a full 5v on the NRF24, it doesn't work, but when you power with 5v on RAW, you get ~3.5v on Vcc, so the NRF24 works (the atmega328p is out of spec at 16MHz and
I recommend the black CH340G USB serial adapters with the 3.3v/5v switch, or the green ones with the micro USB connector. Searching CH340G 6pin on ebay and looking carefully at the pictures is how I find them, about $2/each.
(sorry for delay - typed this two days ago but forgot to click post)
DrAzzy:
RAW requires 7v minimum (well, maybe 6.5) to get 5v on the output, as that's the input to the regulator.
If supplying with external 5v, you need to connect it directly to Vcc.
The NRF24 is a 3.3v device. powering it with 5v may damage it. If you want to use it without level shifting, you should use a 3.3v pro mini (and a 3.3v serial adapter - the power line of the serial adapter is connected directly to the power rail, so a 5v serial adapter on a 3.3v pro mini will result in the pro mini running at 5v)
It may be that what's happening is that when you get a full 5v on the NRF24, it doesn't work, but when you power with 5v on RAW, you get ~3.5v on Vcc, so the NRF24 works (the atmega328p is out of spec at 16MHz and
I measured the Voltage. I think you are completely right. When powering via RAW, I get about 4.65V which seems to be possible for RF24 to run. When I add it to 5V, I have 5.16V which seems to much. At all I damaged the RF24 module when running for a longer time with 4.65V.
I thank you very much for your opinion. I will use 3.3V Arduino pro mini as you suggested.