Hi!
I have bought a TC35 GSM module with a 2.65V UART.
What is the best way to convert the 2.65V TX signal from the module to a 4-5V signal?
I have thought about using 2 transistors. RX 2.65V -> resistor -> NPN -> resistor -> PNP -> Arduino TX
Another idé I have is to use a PS2501 optocoupler.
Will it work? Any better solution?
A small MOSFET and a 2K7 to 5K pull-up resistor on the drain to 5V should do it. The 2.65V TX signal to the source, gate directly to the 5V supply. Even a ubiquitous 2N7000 might be just fine, but something like an SI2300DS would be real nice if you are handy with soldering SOT-23 devices.
olof_n:
I have bought a TC35 GSM module with a 2.65V UART.
What for? An Arduino will recognize a 2.65V signal, no problem.
fungus:
What for? An Arduino will recognize a 2.65V signal, no problem.
Well, I am not saying it won't, but if your running your Arduino at 5V the ATmega328 spec sheet says that the minimum guaranteed VIH is .6Vcc. That's about 3V. It may work directly, but then again it might not.
Just sayin'
Thanks for the replies!
I don't have any small mosfets (only a couple of IRL540).
Any opinions about using transistors (basic parts like 2n2222 and BC327) or optocoupler? Will it work?
/Olof
Yes, you should be able to do it with a bi-polar transistor too.
See the attached schematics. I show both Bi-polar, using a 2N2222 and MOSFET, using 2N7000.
The nice thing about the MOSFET is that it can be used bi-directionally whereas that is not going to work with a bipolar transistor. I know you don't need bi-directional capability for this problem, but it might come n handy at some point. Might be an idea to keep a few small MOSFETS around. Here is a short article about it: http://www.aztecmcu.com/id88.html
Thanks for the schematics!! I will try that.
The mosfet solution can be useful in the future.
