arduino hack

I have brought the arduino pro mini. It's IO pins gives 5V. I wanted 3.7V. There's an onboard voltage regulator mic5025 and has 5 pins. I wanted to know if I can cut the traces and add a 3.7V regulator and if so what precautions must be taken. Also I can't use the 3.3V arduino pro mini cause I required 3.7 V only and no lesser.

0 royston02 over 11 years ago

link-
Arduino Pro Mini V1.2 mega168 5V/16MHz 8 Analog Interface
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0 Workshopshed over 11 years ago

The key difference between the 3.3v and 5v versions is the timing crystal. The higher voltage allows it to run at a higher clock speed, this also means the bootloader software in the chip is coded to work with that speed so functions like millis are correctly calibrated. I suspect that trying to run a 3.7v with the higher speed will lead to instability.

Starting from where you are I'd use a voltage booster module or chip to get your supply upto 5v to run the pro mini and then use a level shifter circuit (perhaps a simple resistor voltage divider might work) to ensure that the outputs toggle between 0 and 3.7v. If you are communicating at a higher speed then you might need a more sophisticated circuit.

Alternatively use a 3.3v device and use transistors to boost the output voltage of the I/O

Also check the data sheets of the device you are connecting to. For example a some of the Ethernet chips have a 3.3v supply but can work correctly even if the data lines are at 5v. So you might find you can use your circuits without change.

Level Shifting Digital Signals - Application Note - Maxim
Incredible DIY: Simple 3.3V–5V level shifter
Code and Life – Level Shifting 101
Voltage booster Product LinkProduct Link

Here's a page that looks at power saving. It does suggest running at lower voltages is a possibility. For 16Mz (the clock speed of the 5v) version it recommends 3.78v so you might just find you can get away with it.

Electronics : Microprocessors : Power saving techniques for microprocessors

You just connect the supply voltage to VSS (rather than RAW), no need to cut any tracks.

Note for programming etc you probably want to use 5v.
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