Temperature sensor input to Kanalog?

[mmurray70]

Hi guys im trying to get Kflop to control the spindle chiller on my Fadal mill. My machine has an ambient temp sensor and a coolant sensor and when there is a 2 degree difference it turns on the chiller.

Should be fairly easy to feed signal to an analog input but I cant find any info about how to power the sensors, and I dont even know enough to make a good guess. The sensors have no markings and they have three wires, a ground, power and signal. Best info i can find is they are fed a "REF" voltage thats comes from 12v through a resistor which could be anything. I dont want to fry the sensors. I tried powering the sensor with an AA battery and I got about 0.7 volts out and this increased when heating sensor slightly which is a good sign.

Anybody here have any knowledge of temperature sensors? Think im safe to power it with 5v or do i need to reduce it down somehow?

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[TomKerekes]

I have no great ideas but here is what I would do:

Measure the device with an ohm meter/diode mode (all 6 ways) to try to determine if it is something like a thermistor + resistor or something more complicated/integrated with an amplifier.

Power with 12V through a resistor (1K) to limit damage if too high voltage and check how much current is being drawn.

A thermistor is commonly used in a voltage divider circuit with another fixed resistor with a Reference voltage being applied to the voltage divider. That's what we do with our KNozz board for measuring the Nozzle temperature for a 3D Printer using it's thermistor. Those Thermistors are about 100Kohms at room temperature and go down to about 10K at 100 degrees C. See the Thermistor section here:
KNozz Connector Descriptions

Good luck
Regards

[mmurray70]

I guessing it might be something more complicated. I dont get a resistance reading in any of the 6 combinations. If I set meter to diode mode i get no reading in 5 combinations and i get 1.75v with positive lead on positive input and negative lead on signal out. Current is not measurable on my fluke 12E (goes down to microamps) when powering through 12v battery and 750 ohm resistor. Does this give any more clues?

I think im going to try powering it with 5v from my machine through say a 500 ohm resistor and see if i get a usable output. If not ill keep dropping resistance and if it blows up ill just have to find another type of sensor. This sound like a reasonable plan?

[john-100]

what do the sensors look like ??

some thing like theTMP36GT9Z ?



PDF data



John

PS

may be you can adapt this from the data sheet








PPS
second thoughts a LM335Z adjustable temperature sensor could be closer

PDF data

[TomKerekes]

I think im going to try powering it with 5v from my machine through say a 500 ohm resistor and see if i get a usable output. If not ill keep dropping resistance and if it blows up ill just have to find another type of sensor. This sound like a reasonable plan?

Sounds reasonable to me. I'd also monitor the voltage across the device and 500ohm resistor to determine the current and voltage.

It should be easy to determine if it is a device like John posted. The output should somewhat clamp at some zener voltage in that case.

Regards

[mmurray70]

I dont have much to go on, the actual sensor is buried inside a coupling nut and covered in some kind of glue. So no idea what it looks like. Probably is something like the ones you mention John. I will let you guys know how it works out. Could be a few days or more before i get a chance to try it.

[mmurray70]

Hi Guys,

I got the chiller working with Kflop control! I powered the sensors with 5v through a 390 ohm resistor and fed signal into kanalog and got around 3.800 volts. Voltage would change in 0.004 increments based on temperature. Im guessing each increment might be a degree? But not really sure. At least it gives me a voltage thats changing that i can use to control it.

Did a little program to compare temperature and delay starting chiller since it needs 3 minutes for pressure to equalize before restarting. Also added a delay to stop, to force chiller to run for a period of time. And it all seems to be working great. Thanks to those that helped. Heres the code im using incase it might help somebody sometime:

// From Spindle chiller on off timer
int timechiller = 0;  // for spindle chiller timer
int timehot = 0;  // for spindle chiller timer
int Hot = 0; // for spindle chiller, 1 if coolant hot, 0 if normal
double ambienttemp = 0;
double coolanttemp = 0;
double tempdiff = 0;
// End spindle chiller timer


for(;;)
	{	
		// Spindle chiller on and off	
		
		coolanttemp = KANALOG_CONVERT_ADC_TO_VOLTS(ADC(4));
		ambienttemp = KANALOG_CONVERT_ADC_TO_VOLTS(ADC(5));
		tempdiff = coolanttemp - ambienttemp;
		if (tempdiff > 0.01)
		{
			Hot = 1;
		}
		else
		{
			Hot = 0;
		}
		
		int TT=Time_sec(); // get current Time_sec		
		if (timechiller != TT && Hot == 1) // if coolant too hot and one second passes, add 1 to timehot
		{
			timehot = timehot + 1;
			timechiller = TT;
			//printf("Hot. temp difference is %f\n",tempdiff); 
		}		
		if (timechiller != TT && Hot == 0) // if coolant normal and one second passes, subtract 1 to timehot
		{
			timehot = timehot - 1;
			timechiller = TT;
			//printf("Normal. temp difference is %f\n",tempdiff); 
		}		
		if (timehot > 180 && !ReadBit(55)) SetBit(55); // if timehot greater then 180 sec and chiller off, turn chiller on 
		if (timehot < -300 && ReadBit(55)) ClearBit(55); // if timehot less than time off and chiller on, turn off
		if (Hot == 1 && ReadBit(55)) timehot = 1; // if Hot and chiller on, reset counter to 1
		if (timehot < 1 && !ReadBit(55)) timehot = 1; // if timehot less 1 and chiller off, reset counter to 1
		// End Spindle chiller on and off
	}