my soldering iron uses 2 wire thermo coupler. How can i get the variables i need to make a function using map to display aprox temperature?
at about 73f the thermocoupler reads 4ohm and resistance increases with temperature.
You should know the type of the sensor, is it Pt100 (unlikely), a thermocouple (which?) or a PTC resistor?
For a resistor build a bridge (voltage divider) and measure the voltage with the Arduino. For 4 Ohm sensor resistance you'll need a bridge amplifier/ADC like HX-711.
A thermocouple needs special interface hardware for reading the very low thermo voltage.
could i get away with just a voltage divider?
I measured not sure of the exact temp but it seems like solder begins to melt at 70 ohm and about 100 ohm is the hottest i would need it. So it seems like the useful range is roughly 30-110 ohm.
Knowing this, would a 100ohm resistor for the voltage divider be a good choice?
Could i just simply use the voltage divider circuit to read the ohm of the thermocoupler. trying to make a simple as possible. Im sorry i feel like this question is becoming out of topic. I still need find a solution to convert ohm to aprox temp range .
i was reading https://www.circuitbasics.com/arduino-ohm-meter/ and was going to start here but i wanted to gather a bit more information
Yes. Consider that the current through the divider will start then with 50mA at 4 Ohm (cold) and 5V. A higher resistor is usable as well, and the built-in 1.1V ADC range may be fine as well.
Okay so when i read my resistance value with arduino i can then use min and max values to map between low and high temp range? i might as well just use 0-500% until i can read real temp. i can only really read room temp or possibly boiling temp.
It's all up to you, I don't know more about your sensor and capabilities.
Well i setup ohm reading circuit and i can successfully read various resistor values correctly but now im not able to read the value of the thermocouple like i could with my multi meter?
I don't understand what you mean. If you can read resistor values and the sensor is a resistor, where is your problem? Of course you have to map() resistance to temperature.
I took the iron apart i see nothin fancy just the symbols and wires for the thermistor and coil. but i sure cant read it with the arduino. it just stays at 1.5 - 1.9. when i short the arduino meter it reads 0.15 ohm
I used a 200ohm resistor if that matters. im using 5v as ref
Then it may be a thermocouple, not a resistor.
how come the handheld multi meter can read it but the arduino cant?
Which resistance do you get if you reverse the cables?
it appears to read the same both ways.
i dont understand why the multimeter would read it but not the arduino. i have op amps, not sure if they would work, but before i get involved in that i think i need to understand whats happening right now
Did you measure reverse with your DVM? Also try DC volt/ampere
i did reverse but i didn't try to measure voltage. It has all the signs of being a thermocouple it seems. I have never worked with a thermocouple like this so i don't really know what to expect. i am stumped as to why the arduino cannt read the resistance value. I wish i knew exactly what it was and why my multimeter reads a range of resistance but not the arduino.
Is it normal for a thermocouple to read like this? i guess so
A thermocouple produces a voltage. It behaves differently with different ohm meter circuits.
Do you know of a sure way i can tell if this is really a thermocouple "without smashing the ceramic off the iron", im worried it looks like there are different amps for type k and type s. I have some ph sensor amplifier/reading board and some op amps id have to dig out, does it matter really what op amp i use, i wonder if the ph module boards could be used lol, i also have some optical dc dc converters. This entire project is running off a 18v battery
I wish i would have just posted this in general electronics, i had a feeling it was going to turn into this
Hit the flag icon and ask the moderators to move it for you.