# How to connect digital temperature probe (NTC 10K) with two wires, to RPi 3?

I recently was given a Raspberry Pi 3 kit, and also a package of temperature probes that are two wire with a plastic male connector. I haven't come across any wiring diagrams or images of how I might be able to connect one to a breakout board specific to RPi 3, and test its output.

I'm looking for some guidance as to how this might be done. I've had no problems coding DS18B20 in python or C, and the other sensors I've tried were 3 wire. I've also worked through modprobe w1 tutorials for DS18B20 without problems either.

I don't quite understand how you get the signal, 5v power, and ground set with just the two wires. I considered perhaps power/signal shared a wire, but I'd have no clue about such things, and don't want to damage my RPi3 device. I'm a total noob when it comes to sensors! Coding I can deal with.

These are 5v devices as I understand the documentation.

I do have a project that would make fairly good use of this type of probe, but I'd like to learn how to connect these to a Pi board for prototyping.

Thanks!

The NTC 10K is a part number for a thermistor, i.e. its resistance varies with temperature.

You can't connect it directly to the Pi.

You will have to design a circuit to vary a voltage according to the resistance and measure the voltage with an ADC (Analogue to Digital Converter) which you connect to the Pi.

• Thanks- Indeed! Build a circuit. Any ideas what that might look like? Or perhaps steps? Mar 22, 2017 at 21:26
• @gary7 Not my field. I'd check out Arduino and such like for examples.
– joan
Mar 22, 2017 at 21:30
• So this would be 10k ohm, and Pi doesn't measure resistance - therefore the ADC. OK, so the resistance is the measure we want, and means the resistance should be converted to voltage, yes? So, to do that, I would add a "stationary" resistor in series, and measure the voltage between them. Question now is what resistor to use? Another 10K? I have the conversion code and equations to do the work, but I'm not sure how to select the "stationary" resistor value. Any ideas about breadboard layout would be helpful too! Mar 22, 2017 at 21:40

there are boards which you can use to connect your NTC and these boards gives 4-20mA current loop output. Once you have a current loop output you can use a 4-20mA current loop receiver and you should be able to read the NTC output. It will work something like this. raspberry pi 4-20mA receiver