Just to make sure,
When using USB or P+/P-, I need the jumper set to usb/bat, and the voltage can be up to 17V, and the imp board lowers it to 3.3v, regulated.
when using the VIN/GND, I can send up to 17V, the imp board lowers it to 3.3v, regulated, and I dont need the jumper, it works any way.
so far, correct?
If I attach 9v to usb/p+p-, what is the voltage i get on vin-gnd? 9v or 3.3?
Just to make sure,
Which or impee board is your question about ?
If you attach 9v to P+/P-, VIN-GND will be 9v.
3.3v is on the 3.3v pin (that’s the output of the regulator). VIN is the input of the regulator.
can i get the imp (april board) to report the Vin? I want to put two thermistors on one imp and use 3v3 and vin pins but hardware.voltage() gives the device voltage
You can have as many as six thermistors on an April board. Just connect one leg of each thermistor to 3.3 and the other to the input port. Also connect a resistor between each input port and GND and you’re set. That’s 6 thermistor and 6 resistors (or any smaller similar combination). You can read hardware.voltage() to correct for any small changes in the 3.3v supplied to the thermistors. You end up reading the voltage drop across the 10K resistor. If you use 10K NTC thermistors and precision 10K resistors, you end up reading the voltage drop across the resistor which reflects the temperature being sensed by the thermistor (instead of a reverse relationship). There are several other approaches and it’s kinda what you prefer.
Fab! Thank you. It’s working! now off to hack my boiler
If you want to measure Vin you have to set up a voltage divider yourself to drop it into the 3.3v range of the imp inputs. This divider takes some current of course, which only matters if you are aiming for battery power which I don’t think you are. One great feature of MakeDeck’s latest C3V0 board is the provision of this divider on board, controlled by an output pin and a FET to switch the power.