Hey all, I'm trying to trigger a pin on an Arduino Nano (v3) using 11-15V. I've come up with the diag below, but am not sure if this is: correct (i.e. R1 and R2 values?) the most efficient way to "tell" the Arduino light the LED. Basically, I want to be able to detect 11-15V on an Arduino pin, a…

dephwyggl: Hey all, I'm trying to trigger a pin on an Arduino Nano (v3) using 11-15V. I've come up with the diag below, but am not sure if this is: correct (i.e. R1 and R2 values?) the most efficient way to "tell" the Arduino light the LED. Basically, I want to be able to detect 11-15V on an A…

Remove R2 (collector directly to pin D2). Use INPUT_PULLUP in pinmode. Change R1 to 100k. Or, like Jack said, use a 1:2 divider. This is the safer way. No problems if you accidently set the pin as output. Leo..

As Leo said, it might be "safer" to use a wiring that does not present any opportunity for damage if you happen to power up you arduino with the pin configured as an OUTPUT instead of an INPUT.

Or, you can forget the arduino and get by with a resistor and a transistor. [schematic.jpg]

Or, you can forget the arduino and get by with a resistor and a transistor. except for one little detail.... I'm trying to trigger a pin on an Arduino Nano (v3)

Man, you guys all rock! :grinning: jack wp: Not sure how I missed the voltage divider approach - probably thought the output V would be too variable for the Arduino, but nope; it's workable. I'm going with that, and, as the 11-15V can be noisy, will be adding a (zener/resistor?) over-voltage protec…

dephwyggl: ...will be adding a (zener/resistor?) over-voltage protection bit to protect the Arduino pin. Zeners don't work as overvoltage protection. The Arduino might be off at some stage, and then a zener is useless. Pick the resistor values so high that the "hot" resistor can't send more th…

A bit of background: I have programming experience, but am new to Arduinos and designing electronic circuits generally. I have a basic understanding of electricity and am learning (quickly!) about digital circuits and interfacing with analog systems. I hugely appreciate everyone's suggestions and he…

A 5volt Nano needs at least 6volt on Vin, because it's pre onboard 5volt regulator. 7-12volt is recommended. You're giving it 5volt - 0.7volt (diode drop) - ~1volt (regulator dropout) = ~3.3volt. It might work on that low (out of spec) voltage, it might not. R3 is not needed if you enable the int…

11-15V to drive 2N3904 base

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jackwp November 23, 2015, 11:51pm 2

Drop the transistor, and just use a pair of resistors as a voltage divider.

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11-15V to drive 2N3904 base

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