Converting emontx 2.2 from 3.3v to 5V

What's involved in changing the standard emonTX from running at 3.3V to 5V. Do I just change the Microchip MCP1702 to ?? or to other components need to change too, so that the current and voltage sensing works correctly.


Robert Wall's picture

Re: Converting emontx 2.2 from 3.3v to 5V

First of all, why? As you're struggling for input sensitivity, you're actually going in the wrong direction - or are you thinking that your S/N ratio will improve? I don't think anyone has done a carefully controlled comparison to check the effect of the supply voltage on performance.

The only difference it makes to current and voltage sensing is you need more volts at the input pins to use the full range of the ADC, that's easy enough with the voltage but the current means a higher value burden resistor which will worsen the errors in the CT.

If you have the radios installed, their maximum recommended operating voltage is 3.6 V for the 69CW and 3.8 V for the 12B, so the radio will still need a 3.3 V supply, and you'll need to step down the inputs to it, as is done in the emonTx Shield.

glyn.hudson's picture

Re: Converting emontx 2.2 from 3.3v to 5V

emonTx shield runs at 5V with level shifting for RFM12B / 69CW, maybe this would work best for you used in conjunction with an Arduino Uno / Lenoardo. 

bruce_miranda's picture

Re: Converting emontx 2.2 from 3.3v to 5V

I am not using the RF module on the emonTX but I thought running the board at 5V would be better but it sound like it may not be such a great idea after all. 

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