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Heating elements for own built terranium

Alec_t

Jul 7, 2015
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The triac arrived but it was f* faulty. The output voltage remained 240V at any setting of the rotary variable resistor.
A phase-controlled triac does not reduce the mains peak-to-peak voltage; it chops the mains voltage and so reduces the RMS voltage. Depending on your measuring equipment you may not have detected that.
 

GPG

Sep 18, 2015
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Sep 18, 2015
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Check ,after removing the supply!! if the triac is shorted.mt1 to mt2
Is the only load the bulb or do you have the heater in parallel
Doyou have the circuit/layout?
 
Last edited:

Tinker Unique

Dec 1, 2014
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Dec 1, 2014
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Possible solution = 110v "heat-tape" used to keep water pipes from freezing during the winter. Sold in most Hardware stores. Can be "woven" around on the bottom ( like an electric blanket) of the terranium below the soil/sand. OR go to a commercial greenhouse ( supplier) to find out what they use.
 

Stephen Mifsud

Sep 29, 2015
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Sep 29, 2015
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A phase-controlled triac does not reduce the mains peak-to-peak voltage; it chops the mains voltage and so reduces the RMS voltage. Depending on your measuring equipment you may not have detected that.

Alec_t you are right. While my voltmeter and bulb did not alter the volatage or luminosity, when I connwcted it to the filament heaters, it did the job smoothly. There was no problem with the triac

Check ,after removing the supply!! if the triac is shorted.mt1 to mt2
Is the only load the bulb or do you have the heater in parallel
Doyou have the circuit/layout?
Thanks GPG, read above, took your suggestion and helped.


Possible solution = 110v "heat-tape" used to keep water pipes from freezing during the winter. Sold in most Hardware stores. Can be "woven" around on the bottom ( like an electric blanket) of the terranium below the soil/sand. OR go to a commercial greenhouse ( supplier) to find out what they use.
We dont have freezing temp in my country !
 

Stephen Mifsud

Sep 29, 2015
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Sep 29, 2015
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Ok so far I am happy with the thermostat and heating. Now comes problem 2. I want to incorporate a DC circuit to light spotlights, DC bulbs and PC fans. I ripped off the PSU of a microwave (mostly to use its transformer) and made a simple bridge rectifier. The voltage after the rectifier a schotkey type (STPS30), was 24V and I was afraid that it is too much for the input of a voltage regulator: L78512 (or L78S12). So I placed an 18V zenner diode before the input. At rest, I had a nice 18.3V input and 11.8V output. However when I connected a bulb or a fan, I had very low power :-( :-( The fan needed a finger flick to rotate a bit, and the bulb was dim.

I used R of 500Ohm. When I used 200Ohms, the resistor was a bit hot (maybe because 0.25W).
IMG_0492.JPG

1: What is the ideal value for R? One of the fans is 0.44A, another is 0.13A (the one I Tested), while the bulb was 4W (12V) I would probably need to connect two bulbs and two fans.

What is limiting my power in this circuit????

The transformer is WDB4109 from DongGuan WanXing
IMG_0489.JPG
 

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GPG

Sep 18, 2015
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What is limiting my power in this circuit????
The resistor.The 78s12 is good for 35Vmax.. Your diagram shows the secondary connected to ground? This is half-wave. Does the secondary have a centre-tap?
 

Stephen Mifsud

Sep 29, 2015
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You are right, the STPS30 is here operating as half-wave. I've modified the circuit and used a full wave rectifier Ic and fed its output directly to the 78s12 (hence eliminating the zenner and resistor) and a 1000uF smoothing capacitor. I managed to have my bulb lighting at full amperage (0.5W) without the flickering resulted by half wave rectificiation/
 

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