 Can high M-ohm resistors damage arduino?

Hello all – I’m working on a project, (using arduino mini pro) creating a touch sensor that modulates tones that are played. My setup is super basic, I’m running power from VCC through a 1Mohm potentiometer. The output of that potentiometer connects to one side of a 1Mohm resistor, and the other side of that resistor connects to Analog pin 0. Also connected to the A0 side of resistor is a wire that leads to a plant, this is the touch sensor.
I attached some images to clarify if this /\ is confusing

I’ve found that when I daisy chain the 1M-ohm resistors, about 5 in a row, the touch sensor is more sensitive - so I went out and got a single 10M-ohm resistor. I don’t know much about electronics, I’m learning as I’m going, but have read that high resistance creates heat - and am wondering if 10M-ohms of resistance between VCC and Analog pin 0 on the Arduino Mini Pro could damage it or put too much strain on it?

Appreciate any words of advice you can offer, thanks!

but have read that high resistance creates heat - and am wondering if 10M-ohms of resistance between VCC and Analog pin 0 on the Arduino Mini Pro could damage it or put too much strain on it?

No it is current flow that generates heat and with a 10M resistor you have f**k all current flow. Your arduino is quite safe.

ryanvh22: I don't know much about electronics

I can tell by this question.

The LOWER the resistance the HIGHER the current, the GREATER the "strain" on the Arduino.

Not that any of that has the slightest bit of meaning anyway, as the Arduino's analogue input has a high impedance anyway, so a dead short to Vcc will still not put the slightest "strain" on the Arduino.

Resistance vs. heat is an interesting relationship. As current goes up, more voltage is dropped across the resistive element. This voltage is dropped as heat. So a 0.0001 ohm resistive element will create less heat than a 0.1 ohm resistive element -- provided current draw is fixed at some amount.

OTOH, if the source voltage is fixed, then as resistance goes up, current goes down. So, despite the increased voltage drop, there's less current flowing through a 1000 ohm resistor than a 1 ohm resistor, and as such, the 1k ohm will run far cooler.

This is why resistors are often rated in watts... a function of both current and voltage.

But, as Grumpy_Mike said, input pins have an extremely high resistance -- to which you're adding 10M ohms, which is another extremely high resistance. As such, there is very very very little current flowing through that signal chain. Since current is half the equation, the voltage would have to be extraordinarily high to make the heat load consequential in the slightest. Certainly way more than the 5v you'll be applying.

Or in maths:

V = I R

P = V^2 / R = I^2 R

Plug in 5 volts and 10Mohms and you get power = 2.5 microwatts, current = 500nA

Those are levels you'd be hard pressed to detect, let alone be damaged by. Fortunately CMOS inputs as in the Arduino are very sensitive to extremely small currents (since the input resistance is far larger than 10Mohms). However the protection diodes on the inputs will swallow upto a milliamp or so without risk, so 500nA isn't any sort of strain.

Thanks guys, these are all really helpful answers, still trying to wrap my head around the relationship between Watts, Amps, and Volts but now I at least know, my ignorance isn't hurting my hardware ;) in this case at least. Thanks!