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draculic acid69
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[*] posted on 1-8-2019 at 06:13
Mantle transformer question


If my 1litre mantle is rated at 400w and it's 240v would it be a reasonable assumption that the transformer which is a 220v to 12v would be rated a about 1.5amps. the math says 1.25amps but I'm allowing a little bit more coz it has led's and the stirrer which with the weight of the magnet probably takes 500 milliamps at 12v I'm guessing or would the transformer be like 3amps or higher.the reason I ask is because the transformer is all in Chinese. The only English says 220v-12v apart from the model number.google search on model number yeilds nothing.how many amps do other people's 1litre mantles transformers put out.sometimes it's on top of the transformer.
If anyone can open up there mantle and have a look it would really help.
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Sulaiman
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[*] posted on 1-8-2019 at 07:04


you can make a fairly accurate determination of the transformer wattage rating by weight !

Weigh your transformer then look online for a similar design and weight.




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[*] posted on 1-8-2019 at 07:15


Quote: Originally posted by draculic acid69  
If my 1litre mantle is rated at 400w and it's 240v would it be a reasonable assumption that the transformer which is a 220v to 12v would be rated a about 1.5amps. the math says 1.25amps but I'm allowing a little bit more coz it has led's and the stirrer which with the weight of the magnet probably takes 500 milliamps at 12v I'm guessing or would the transformer be like 3amps or higher.the reason I ask is because the transformer is all in Chinese. The only English says 220v-12v apart from the model number.google search on model number yeilds nothing.how many amps do other people's 1litre mantles transformers put out.sometimes it's on top of the transformer.
If anyone can open up there mantle and have a look it would really help.


You probably can get an estimate of the transformers VA rating by comparing it size to other transformers of know VA rating.The VA rating is the output voltage (rms) x the maximum output current (rms). You could also consider the motor rating to determine the rating of the transformer.

If your going to replace the transformer with something else you should consider a safety margin again on its power rating.




i am wg48 but not on my usual pc hence the temp handle.
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draculic acid69
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[*] posted on 1-8-2019 at 07:28


The motor is a 12v DC w/ no writing on it.cant take it out of its plate mount.
Is the stirrer motor what you were talking about.or is a motor rating something else.
Also what kind of safety margin were you thinking?


[Edited on 1-8-2019 by draculic acid69]

[Edited on 1-8-2019 by draculic acid69]
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draculic acid69
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[*] posted on 1-8-2019 at 07:51


Quote: Originally posted by Sulaiman  
you can make a fairly accurate determination of the transformer wattage rating by weight !

Weigh your transformer then look online for a similar design and weight.





This is the same design same size shape and colour only difference is there's English instead of Chinese writing.it seems to be the same size as anything from a 500milliamp to 3Amps. I was guessing that it was around the 1-3amp mark but guessing don't help me much.ill weigh it tomorrow.

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draculic acid69
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[*] posted on 3-8-2019 at 01:08


It weighs 224.8g with the wires cut off so add a few grams. It's 44mm wide 33mm high and 22mm deep on the steel casing.
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Sulaiman
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[*] posted on 3-8-2019 at 03:56


About 6 VA.

See if you can find a slightly higher wattage transformer, e.g. up to 12VA, that can fit in the available space.




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[*] posted on 3-8-2019 at 04:50


Ok according to some VA to Amps calculator 12VA at 12v equal 1amp.so the whole mantle runs off an amp or two.6VA equals 0.5amps which just seems way too weak.two amps should be a good amount to start with.

[Edited on 3-8-2019 by draculic acid69]
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[*] posted on 3-8-2019 at 06:28


The transformer is mainly to power the motor,
the heating element will be a much higher power independant of the motor.

12 Vac 6 VA = 0.5 Aac
after rectification about 0.3 Adc maximum will be available,
the dc voltage will be about 14 Vdc maximum
(sqrt(2) x 12) - voltage losses in diodes and circuitry.
So the maximum motor power will be about 4 Watts,
which is typical for small dc motors.




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[*] posted on 3-8-2019 at 08:19


So what kind of voltages and amps go through the nichrome? Is the nichrome element running on d.c. or AC? I've tried tracing where the power goes through the circuit board but I get lost with the voltage regulators and diodes.
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Sulaiman
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[*] posted on 3-8-2019 at 10:09


The heater is powered by ac line voltage, not via a transformer.



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[*] posted on 3-8-2019 at 17:51


So it's running at 240v and however many amps it takes to get to how hot its dialed in to be? This I could not figure out for the life of me, I tried tracing the current around the board and made it to the voltage regulator where it seems to go in two directions.the way this thing works confuses the shit out of me.so the motor is the only thing that needs a transformer? So the potentiometer dials have AC running through there tiny wires? The little led's have to be DC right? Either way I think I just made a decision: no repairs on the board and screw the transformer.im gutting it and going with cheap control boards for the motor and thyristor or dimmers for the element.

[Edited on 4-8-2019 by draculic acid69]

[Edited on 4-8-2019 by draculic acid69]
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[*] posted on 3-8-2019 at 20:48


To control the heating element you only need one of the dimmer modules.

To control the motor you will need a pwm controller AND a 12 Vdc supply.
The 12 Vdc supply should be capable of supplying at least 300mA, I suggest more (e.g. 500mA or 1A or more)
You can use batteries, plug-pack (wall-wart) supply, an old laptop power supply (even if the supply is up to 19 Vdc), or a dc power supply.

The wiring can look messy with three external modules
(dimmer, pwm, dc supply)

P.S. if you do buy a new 12V power supply consider getting one that can also power a small water pump simultaneously, if you think that you may use recirculating water (maybe with ice) for cooling your condenser(s).

a 12V or more battery with charger is a good lab power supply as it allows your water pump to operate in case of a.c. power failure.

[Edited on 4-8-2019 by Sulaiman]




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[*] posted on 3-8-2019 at 22:14


I already have a little 12v motor control board I can hook up.it will fit inside easily.ill just run wires out to power pack externally.i care not for looks but that doesn't mean I won't try and do a nice neat job.the thyristor circuit and motor control board should both fit inside.will get a dimmer if the thyristor isn't as fine at handling the lower temperatures that I need.i have plenty of 12v power packs lying around.i also have a old ATX power supply from a computer that's running my extraction fan. It will power other things easily in the future like stirrers and vac filtration pumps.
As for water pumps I had a little 12v one but it was so weak it barely made it up the hose to the condenser.replaced with a 240v one.all is now good with pumps.
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[*] posted on 4-8-2019 at 04:30


The transformer will power the brains and the motor and that is it.

The brains then acts as a pwm switch for the element, the elements resistance determines its power draw/dissipation, this is determined by the gauge and length of NiChrom and its specific alloy.
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