SSR controlled heater setup query

900turbo

@jay_s_uk Its a mains heater , so I was in belief of using EXT_5V_IN via the SSR to control it as this was how it was setup on the original board.
What do you mean by "you can just use a heater (as long as the input voltage is less that 32v) or fan output (set to 12v if the input voltage is greater than 32v) to control that then"

Thank You.

jay_s_uk

@900turbo the thermistor is probably a 100K NTC 3950
and use a heater or fan output to control the SSR as thats the usual way.
see here https://docs.duet3d.com/en/User_manual/Connecting_hardware/Heaters_bed#bed-heater-driven-using-a-solid-state-relay

droftarts

@900turbo said in SSR controlled heater setup query:
I can't really tell from the picture what the sensor is, though heater pads do often use a thermistor. Take the resistance readings and report back.

Am I wrong wiring the SSR Control to the EXT_5V_IN connector then ?

No, it is supported. Though if you want to turn off the PSU, it's best to use pson for that. As @jay_s_uk says, you can use a heater or fan output, or even an IO pin, so long as the signal voltage is within the limits of the input on the SSR (3 to 32V on yours).

Ian

900turbo

@droftarts Okay I’ll show you the current SSR To MB setup

900turbo

This post is deleted!

900turbo

@900turbo

droftarts

@900turbo That looks fine. Like I said, you can use pretty much any I/O out pin (though it is slightly more complicated on the 6XD because of the opto isolated outputs), and the PSON pin is basically just another switchable pin.

Ian

900turbo

@droftarts Just thought I would check.
Thanks for the help Ian.

900turbo

@droftarts
I took the readings at 200ohms

Room temperature 30.2

25 degrees = 30.1

50 degrees = 30.0

70 degrees = 30.1

so only a very slight drop in resistance followed by a rise not sure what this means ?

droftarts

@900turbo said in SSR controlled heater setup query:

I took the readings at 200ohms

I don't know what you mean by that? Do you mean you get 200 x 30 = 6000 ohms? I'm used to modern digital multimeters!

Check you are measuring the resistance of the temperature sensor, by measuring ohms across the two wires that come from the bed. Looking at your picture of the bed, these are the red wires. The second pair of wires, the thicker white ones, are for the heater. Usually, these will be low resistance. Check you're measuring the correct wires, they will be the thinner ones.

For a 100k thermistor, you should get something like:
25 degrees = ~100k ohms
50 degrees = ~33K ohms
70 degrees = ~15k ohms

Ian

900turbo

@droftarts I mean this as in 200 set on the multi meter , there are 5 pins on the heater bed loom of which only 2 produce a reading so I assumed it’s temp sensors wires

Thank you

droftarts

@900turbo can you show a picture of the 5 pins? Try setting the meter to 20k or 200k.

Ian

900turbo

@droftarts at 20 and 200k I don’t get a reading just 0.00

900turbo

@900turbo

deckingman

@900turbo 30 Ohms sounds more like the heater resistance than a temperature sensor. Is it 110V mains or 240V? If it's 240V then using ohms law, 30 Ohms would mean it draws 8 Amps which is about 2,000 watts. If its 110V then 30 Ohms would mean about 3.7 Amps giving about 400 Watts. Do either of those wattage figures sound like the spec for your heater? If so, that confirms that you are measuring the heater resistance, not the temperature sensor. If that's the case, try again with your meter set to read 200K.

900turbo

@deckingman
The heater draws power straight from the PSU at 100-240V so I'm not sure what it draws. However I tried what you said using 200K and got the following results
25 degrees = 128.9
50 degrees = 38.0
70 degrees = 19.0

Thanks for the help!

droftarts

@900turbo With those results, I'd say it was a 100k NTC thermistor, which uses a beta value of 3950. So use:

M308 S0 P"temp0" Y"thermistor" T100000 B3950

For more information on thermistor parameters, see https://docs.duet3d.com/User_manual/Connecting_hardware/Temperature_connecting_thermistors_PT1000#typical-parameter-values

Ian

deckingman

@900turbo said in SSR controlled heater setup query:

@deckingman
The heater draws power straight from the PSU at 100-240V so I'm not sure what it draws. ........................

What I meant was, do you happen to know the wattage of the heater? From Ohms law, if we know the voltage and the resistance, we can calculate the current draw and then voltage x current = wattage. But anyway, it sounds like you've now found the correct pair of wires for the temperature sensor........

900turbo

@droftarts When I use the calculator i get a beta value of 3018 should I use this or 3950 ?

jay_s_uk

@900turbo use 3950