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Extremely basic circuit help required!

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Newbie level 1
Jul 1, 2015
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Hi all,

I have absolutely no idea what I'm doing when it comes to electronics - but I am fairly handy and like to try different projects.

I am attempting to build a small meat drying box.

I want to be able to plug it into a mains socket, and need to power a single light bulb (up to 100w) and a computer fan (on 12v power).

My basic plan is:
Plug from mains into C14 socket -
**broken link removed** (Will I need a fused one like this?)

Cable from power socket to split 2 ways -
- 1 cable goes to 240V AC to 12v DC transformer - then onto a 12v computer fan
Transformer -
12v Fan - **broken link removed**

- 1 cable goes to 2nd switch then onto bulb holder for bulb up to 100w.
Switch - **broken link removed** (I was told I would need a fuse in order to lower the amps before this switch...?)
Holder - **broken link removed**
Bulb - **broken link removed**

My main confusion is coming from what to do with the earth from the mains power cable - the bulb holder and transformer only have 2 terminals...

Would it be better to put the transformer straight after the power socket and find a 12v light bulb - So the whole thing is on 12v? (is there a better way to convert 240v AC to 12v DC?)

I basically need someone to let me know the best way to go about what I'm trying to achieve.

It's early days and I'm nowhere near wiring anything, I just need to define the circuit properly.

I know this is child's play to most on here, but it's my first electronic project and any help would be really appreciated!!



  • Box Circuit.PNG
    Box Circuit.PNG
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A tungsten bulb is underpowered unless you have good insulation, but then life of bulb reduces with temperature rise of glass when enclosed, significantly, like 3000 to 300h. Or drop 50% per 10 'C rise above free air glass temp unless forced with fresh air which adds to heat loss.

This is why Nichrome filament wire is used in toasters and mini ovens. R30 Insulation will significantly reduce power wasted and increase temp rise. Minimal air flow is needed and just dumps wasted power. A metal forced air fan works better used in convection ovens.

So scrap the light bulb and get a minioven or old toaster or use a bunch of 300W tungsten or quartz IR heater tubes or a hair dryer which uses nichrome wire diode and DC motor with current limited by heater wire.

With proper electrical insulation, grounding is not needed. Toasters use Mica insulator wafer to wind the filament wire at one time. Look for this and use insulation that is rated for high temp to prevent outgassing.

Why not buy a meat dryer ?

For drying, a low power is probably desirable. Two bulbs
in series will bias the output to the infrared along with
reducing the power. The old Betty Crocker Easy-Bake
Oven toy used a light bulb (the only things you could
"bake", were specially made mixes, but still). Porcelain
fixtures ought to be fine. Strip out a range you find by
the side of the road, and you've got 500F capable
hardware for the cost of your time.

Anyway, my other suggestion is to skip the 12V computer
fan and buy a 115VAC one, same form factors and all but
now you're free of the need for power supply and so on.
Or maybe you find a cast-off convection oven which has
a suitably high-temp fan. Your alternative is to put a fan
blade on a shaft that comes outside the hot box, and run
it with a divorced motor that doesn't get cooked.

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