[SOLVED] How do I reduce power generated by a heating coil from 1000W to about 100W?

Hi people, I hope I am in the correct section to ask this question.

I'm a student from Malaysia. My situation is as follows: I am trying to utilize a AC heating coil (obtained from a hair dryer) and it operates on two different wattages; 1000W (for full speed hair dryer) and 500W (for half speed hair dryer). How it managed to scale down its voltage to 500W is through a IN5406 diode connected in between the coil and the AC source.

My task would be scaling the power down again to at least 100W or so.
Can anyone recommend me a method to do so? Any help is appreciated, thank you.

Using Transformer or Dimmer.

@ andre_teprom, is there a smaller option?

I was thinking this way: configuring two diodes in series in between the coil and AC source. will this work in order to reduce the power? assuming i got the correct diodes in place to do the job.

I was thinking this way: configuring two diodes in series in between the coil and AC source. will this work in order to reduce the power?

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No chance. Dimmer or better full wave PWM is the only compact option. It's often used for temperature conntrolled hot air guns.

If you rectify the supplied AC voltage, will reduce to half of wattage, achieving 500W to full speed and 250W to half speed.

andre_teprom said:

If you rectify the supplied AC voltage, will reduce to half of wattage, achieving 500W to full speed and 250W to half speed.

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I'm afraid not; the new diode will reduce the power, but the existing diode operated thru' the switch will now not make any difference. The diode is used to chop off alternate half-cycles, which it does; the 2nd diode in series will now serve no useful purpose.

As mentioned, the best, cheapest, easiest way to do this would be to use a triac based dimmer. Building such a circuit would also be easy.

Regards,

Anand Dhuru

HI ard,

I reffered to half-rectifier.

+++

I reffered to half-rectifier.

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Yes. The original poster clarified, that 500 W is achieved with already a half-wave rectifier connected.

Thanks all for the replies. I'll look up on the triac based dimmer and see how it can be done.

Also how about this: what if i replace the diode capable of rectifying more voltage? i looked up the datasheet and it seems 1N5407 can do the trick? the existing one is 1N5406. I'm not really sure which one I'm suppose to look at for rectified voltage: Vrrm, Vrms, or Vdc?
IN5406 Datasheet pdf - 3.0 AMPS. SILICON RECTIFIERS - Jinan Gude Electronic Device

---------- Post added at 18:11 ---------- Previous post was at 17:50 ----------

Can anyone recommend me a diode/rectifier capable of rectifying 1/9 of 1000W? I'm thinking that replacing the existing rectifier is a good solution, unless someone can tell me why I should not carry out this idea. Any feedback is appreciated!

desmond1310 said:

what if i replace the diode capable of rectifying more voltage?

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It makes no difference.
If you rectify an AC supply then you have a half-wave AC voltage, so the result is half the current reaches your (fixed) load. That's what a diode does - it passes current in one direction and not in the opposite direction, which with an AC supply, will pass only one half of it.

desmond1310 said:

. . . . , unless someone can tell me why I should not carry out this idea.

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What difference do you think a different diode would make?

Think of it as a valve in a pipe which only allows the fluid to flow in one direction. If you put a second valve further along the pipe, facing the same way, then they're both just doing the same job. It makes no difference. If you put the second valve the other way round, then one valve prevents current flowing one way, and the other valve prevents current flowing the other way. So no current al all!

As you've been advised, a variable device such as a dimmer for consumer lighting will do the job, provided that its current rating is adequate for the maximum possible load.