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Using Arduino => General Electronics => Topic started by: nicolopadovandev on Apr 24, 2019, 07:49 pm

Title: Convert 3.3v into ampere
Post by: nicolopadovandev on Apr 24, 2019, 07:49 pm
Hi everyone.
I recently bought an RF24L01 radio module to connect it with my arduino esplora.
Sadly the Esplora has the 5v power only, and the module requires no more than 3.3v.
How can I convert these 3.3v into ampere to apply the Ohm's theory?

I also have this chip
Code: [Select]
https://www.sparkfun.com/products/12009
Is this any useful? If so, how do I have to connect it to the Esplora and the Radio module?

Thanks.
Title: Re: Convert 3.3v into ampere
Post by: groundFungus on Apr 24, 2019, 08:35 pm
The level converter is for signals, not power.  I use LM1117 3.3V voltage regulators to convert 5V to 3.3V to power my RF24 radios.  Those regulators provide plenty of current for the radios.  Do not forget the required cap on the input side of the regulator.
Title: Re: Convert 3.3v into ampere
Post by: nicolopadovandev on Apr 24, 2019, 08:58 pm
Is it possible to do this with resistors? And what is the difference between Signals and Power?
Also that chip has 4 channels for signals and 1 for power (the center one) I think.
Title: Re: Convert 3.3v into ampere
Post by: Perehama on Apr 24, 2019, 09:17 pm
A common resistor is not Ohmic, and Ohm's Law is just a rule of thumb. There are lots of sources on the internet that will explain how to do "Logic-Level Translation" using resistors, but It can be a lot of frustration for a new electronics hobbyist if they can't get it to work, or damage their hardware etc.
Title: Re: Convert 3.3v into ampere
Post by: groundFungus on Apr 24, 2019, 09:50 pm
If you are thinking of using a voltage divider to drop 5V to 3.3V, forget it.  As soon as you connect a load to the divider, you change the dividing ratio and therefore the voltage.  Use a proper power converter, ie.linear voltage regulator or buck regulator. 

The power pins on the level converter must be supplied external to the converter, those pins do not supply power.
Title: Re: Convert 3.3v into ampere
Post by: nicolopadovandev on Apr 24, 2019, 11:02 pm
What if I use something like the one attached to this post?
There is 5v input -> 12k resistor -> 3.3v output -> 22k resistor -> Ground
Title: Re: Convert 3.3v into ampere
Post by: groundFungus on Apr 24, 2019, 11:53 pm
One more time, you cannot use a voltage divider to supply power.  See. here (https://learn.sparkfun.com/tutorials/voltage-dividers/all)
Title: Re: Convert 3.3v into ampere
Post by: Perehama on Apr 25, 2019, 02:24 am
One more time, you cannot use a voltage divider to supply power. See. here (https://learn.sparkfun.com/tutorials/voltage-dividers/all)
Also, here (https://learn.sparkfun.com/tutorials/bi-directional-logic-level-converter-hookup-guide), a tutorial and inexpensive translation module, open source, with schematic.
Title: Re: Convert 3.3v into ampere
Post by: groundFungus on Apr 25, 2019, 02:35 am
I give up.
Title: Re: Convert 3.3v into ampere
Post by: WattsThat on Apr 25, 2019, 03:20 am
There is no need for signal level conversion with the NRF24L01, it has 5 volt tolerant I/O but you must supply it with 3.3 volts. The board shown, available on eBay for $1 US is an easy solution for adding the NRF24 radio to a board like an Uno or Nano as it provides a proper 5V to 3.3V regulator, bypass caps and a socket for the module. Easy, simple, cheap.

(https://cdn3.volusion.com/btfzd.umflq/v/vspfiles/photos/AD279-2T.jpg?1479125923)
Title: Re: Convert 3.3v into ampere
Post by: hesam_m on Apr 25, 2019, 11:20 am
Do you want to use a resistor divider to convert the 5V to 3.3V to supply your NRF?

that's not practical because by a voltage divider you limit the current also, or if you use low-value resistors, you put your supply at pressure, because it will be an extra load!

if you want to convert a signal (I/O line), actually it depends on the signal direction. you can use a Mosfet or even yes a resistor divider or a Zener diode.
Title: Re: Convert 3.3v into ampere
Post by: nicolopadovandev on Apr 25, 2019, 09:31 pm
Thanks you! The adapter came with the Radio Module