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Anonymous
Need help setting up digital thermostat. 2017-07-27 01:40:49 Post No. 1216980
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Need help setting up digital thermostat. 2017-07-27 01:40:49 Post No. 1216980
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So I bought this digital thermostat (Model W1209) to use as controller in conjunction with a 120w 12v immersion heater for a small water heater project.
I'm having a little trouble setting it up. My experience with electronics is limited.
Power is through a 230v to 12v transformer borrowed from a tablet.
Here's how I set it up (diagram next post):
Transformer 12+ to 12V+ on chip.
Transformer 12V- to GND on chip.
Jumper from 12V+ on chip to K01 on chip.
Heater negative to GND on chip.
Heater positive to K0 on chip.
Whenever I turn the power on with the heater not connected, everything works fine.
With the heater wires connected, I hear a relay click and the display shuts off.
The thermostat relay is rated for 20A and the heater can't be more than that because it's designed to run off a cigarette lighter.
What am I doing wrong?
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>>1216980
>Transformer 12+ to 12V+ on chip.
>Transformer 12V- to GND on chip.
>Jumper from 12V+ on chip to K01 on chip.
>Heater negative to GND on chip.
>Heater positive to K0 on chip.
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my guess is the power supply cant provide enough current to the device: when the relay clicks on, it drops the power supply voltage, which shuts down the device.
also, temporarily remove the jumper in case you screwed that up in some way.
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oh, wait a minute. you're using the same 12V supply to turn on a 120W heater? that's crazy. you need a really big big supply to do that.
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>>1216992
>>1216990
Thanks. That makes sense.
I don't know how I didn't think of it.
The transformer is only supposed to be temporary anyway. Just for testing.
The final build will be powered by the 12v system in my truck.
Heater is pic related.
The projects I'm building using these little faggots are; heated shower with pressurized PVC pipe "tank", a sous vide cooker, and a winter heater for the diesel tank/injectors.
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>>1216981
>Transformer 12V- to GND on chip.
That's gonna kill the thermostat
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>>1216980
A transformer is AC only, it has no plus or minus. I would use a small 12V DC power supply (wallwart type) that runs the thermostat circuitry and a separate mains to 12V AC transformer to power the heater without any connection between the two. A 120W halogen transformer comes to mind, either a typical toroid or, if weight matters, an electronic transformer. The relay contact then acts like a light switch. There is no reason to use DC for a heater.
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>There is no reason to use DC for a heater.
unless you're in a car, as OP has said.
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>>1217622
yeah that device hes trying to power is a DC heater, notice the cigarette lighter plug on the end.. and not all transformers are AC. all of your wall-wart types are AC to DC that power any low powered electronics. and those transformers DO have a + and - as with any DC output.
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>>1217838
>dc transformer
Technically, that's not a transformer, but a power supply.
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