TL;DR: How can I detect a voltage change from 5V to 10V? I am hoping to retrofit some door/window/motion sensors from an old security system. Using a multimeter I’ve deduced that when “active” the voltage between the wires of each sensor changes from 5 V to 10 V. In reading the docs, it appears tha…

I think I can mark this as solved. The answer is the best one for me, but it doesn’t answer the original question… read lots of the other awesome replies to get at that if needed. As always, the simplest way tends to be the best. Since the door sensor is just a pressure switch (open door = open cir…

A voltage divider should do the trick :slight_smile:

Thanks! Would this be 4 separate voltage dividers probably then, correct? Edit: https://learn.sparkfun.com/tutorials/voltage-dividers Cool!

@Moors7 hopefully you can help me thru my next question with as much ease! Here is (I think) the circuit diagram: [image] When the switch is Open V_AB = 10V. When the switch is Closed V_AB is 5V. (Where A = Node 1, B = Node B, see next pic.) So here’s the circuit I then made to try voltage divid…

@jschwalbe I prefer to use just the INA219 sensor to measure voltage up to 26v and current if you want. [image] INA219 High Side DC Current Sensor Breakout - 26V ±3.2A Max This breakout board will solve all your power-monitoring problems. Instead of struggling with two multimeters, you …

I think this is what you want. [image]

I ended up adding a second resistor after R1 and measuring the voltage between R1 and the new resistor. Turns out it’s either 0 or 3.33 V which is perfect for my application. I don’t think it screws up the alarm system (which I’m not using anyhow). But now to figure out how to use this programmatic…

How clean (free of noise and ripple) is your signal? The ADCs are fast and having a 50/60Hz hum on the signal would explain the volatile readings, while a slow/damping DMM wouldn’t respond to that.

I concur the results suggest that the voltage could be in a wave, notice how the first result is around 100 then its 1 above 3800 and then above 2000 than around 100 and than over 3800, over 2000 and back to around 100. Sure the data set is a small one, but if that pattern continues it would sugges…

Thanks all for your help and thought-provoking questions. It’s a lot for a newbie to digest. I certainly don’t have an oscilloscope (though wouldn’t mind one), so I can’t answer most of the questions. Here are a few thoughts I’d like to try, but anxious that I might break my Spark Core. Can I tak…

Yes, you absolutely need common GND to do proper voltage readings, but whether it’s safe or not to connect the two GND levels depends on the actual setup - so it’s up to your discretion not to cause harm (=disclaimer :sunglasses:). Generally speaking with a 10VDC supply for your sensors connecting …

Need help measuring voltage (10 V)

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RWB July 24, 2017, 11:41pm 17

You can also use this 3 input Voltage / Current sensor to read 3 input sources up to 26v.

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Need help measuring voltage (10 V)

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