Please look over my schematic. Smoked a teensy 3.1 over here...

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ddmods

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This is my first go at drawing a schematic. I can read it. Hope it's good enough for you to read. I destroyed a teensy when it was wired like this. If you can see something I'm missing, it would be greatly appreciated. There's no other way for me to export the schematic and have it readable. I tried. Sorry for having to click... Thanks!

https://www.mediafire.com/?xur31ozm2rizqi8
 
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Good call! I need to add another voltage divider there. I will do that. When the teensy burned, there was no voltage there, though. I will post updated schematic later today.
 
I see you are using a precision voltage source. Check that its actually outputting 2.5v and not sonething else. Also note that aref also has a 470ohm resistor tied to 3v3
 
I double checked the 2.5v voltage reference(shunt type). It was working within spec. @ 2.505v with the onboard resistor/3.3v. I edited the OP with the updated schematic link.

I'm not sure how the voltage divider will work, actually. I'm only reading the difference between A10/A11 when the high voltage circuit is off. It's already in the low mV range. Using the constant current source for 4 wire measurement.

What do you think?
 
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No, now you have 11.1v on A11 when the FET is off.

You'd be better off using a comparitor to measure across the atomizer. You will probably get a better reading that way anyway.
 
But if you want to use dividers just add a resitor to the atomizer side on both a10 an a11 and then middle tap to the analog pins and then another resistor to gnd. Like you did for A10. They will need to be the same values and in the high precision value, like 0.5% to get accurate readings.
 
I see. Is there an example of that somewhere? I thought that's what using A10/A11 was doing. I'm very green to all of this. I tested the difference example in the ADC library with only the constant current source and A10/A11. It worked very well.

You're seriously saving me here. I appreciate it.

EDIT:Oh, I see.
 
Are you measuing the resistance of the atomizer, hence to work out the temperature or the current when its on?
 
What do you think about using another Pfet between the high volage circuit and A10? Before turning on the high voltage circuit, I can send high signal to the gate on the Pfet.

Since A11 is on the - side, would anything else be needed?

EDIT:Just checking the resistance of the atomizer. Needs to work down to like 0.03Ω.
 
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It's for an advanced personal vaporizer. Resistance wire is wound in a coil and cotton is used inside the coil for a wick. Wick/coil is saturated with liquid made of vegetable glycerin and candy flavoring + a tiny bit of nicotine. I feel much better after doing this VS smoking cigarettes.

Idea is to be able to read the resistance of the coil and pulse the mosfet to achieve a desired wattage and/or voltage.
 
Don't think the extra fet is needed if you have the divider.

As for A11. You need a voltage divider. When the Fet is off, the connection on A11 will be 11.1v because thus connection is no longer grounded so has the + potential. And the only path to ground will be through the teensy.
 
Very good, thanks! Too much going on to edit the schematic now, but I'll give it a go ASAP.

You seriously saved me. :)
 
I've been testing with a $3 atmega328p board. I noticed sooo many things wrong with the schematic now and ideas to achieve what I'm trying to do. It's all about learning to me. Thanks again for the help.
 
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