![]() ![]() I was able to solve this issue with a SparkFun 5v Step-Up Breakout*, which boosts the voltage to 5v without any other major issues. One of those times I was accessing sensors that ran on 5v TTL logic, but I didn't have room to place a >5v battery, only room for a LiPo (which generally powers 3.3v). I have used both variants for many purposes, but primarily when working with embedded and small solutions. They provide the Arduino Pro Mini in 3.3v and 5v variants for only $10. I primarily source my components from SparkFun due to their reliability, cheap price and awesome support. If you supply the Arduino Pro Mini 5b with 3.3v the chip will only be underclocked to 8-12MHz, and the voltage for Vcc (the board's operating voltage and what it will power its pins with) will be 3.3v but there is another way. Any other voltage levels should go in the RAW pin. Only regulated 5v power should be supplied through the 5v pin. The 5v version can be powered with 3.3v, but it is not recommended to supply power through the 5v pin, bypassing the regulator. So from that, I conclude that yes, you can run them at 3.3v, but your TTL levels will be just 3.3v.įirst I am going to say it is very much possible. So on a whim (and since I have a ton of these little boards), I changed my FTDI to 5V, and was able to run and program the board just fine. So for a while I just thought they were 3.3v Pro Minis.īut then thinking about it, I realized that having to tell it to run at 16MHz to get the clock right meant it really was a 16MHz chip - which I didn't think was available with the 3.3v model. I even saw that pin 13 was cycling from 0v up to 3.3v - exactly what I was feeding it. So I tried again this time telling the IDE it was a 5v/16MHz chip, and everything ran fine, despite the fact that I was feeding it 3.3v. That told me that it was running faster than 8MHz. I was able to upload programs just fine, but the clock was clearly wrong, as the "Blink" program ran about 2x as fast. I had some generic Pro Mini boards that didn't mark their voltage at all, so I tried programming (and running) them using my FTDI at 3.3v using the 3.3v/8mHz option in the Arduino IDE. ![]() Additionally, at least in my experience, the processor will run at 16MHz and not 12MHz with 3.3v. Also, all your TTL levels (outputs) will be 3.3v, not 5v. Yes, you can run one feeding it 3.3v, but you need to program it as a 5v/16MHz board to get the clock speeds right. I just discovered that I knew the answer to this, because I was accidentally running some 5v/16MHz Pro Mini boards at 3.3v without issue. ![]()
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