# Electronics building a heat out put test dummy

Discussion in 'Modding' started by 1-Man-Army, 25 Aug 2004.

1. ### 1-Man-ArmyWhat's a Dremel?

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as the name says...i was wondering if there are any guides out there on building a device which creates XXX watts which simulates the cpus heat out put....so any one got links to a guide? thx or can whip up a neat circuit sum how for me

2. ### cpemmaEcky thump

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Code:
` +V----100W RESISTOR----0V`

3. ### 1-Man-ArmyWhat's a Dremel?

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is there also a way to make it adjustable(so like 1watt too like 180 or 200watts) with sum kinda rehostat. sorry im kinda nubby at this and also im going to be mounting sum kinda cooling on it.. so it needs to be a flat surface.

4. ### ConKbot of DoomMinimodder

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You could use a variac to vary the output. You don't need a 100w resistor, you can use a 10 or a 25W and just push beyond what you normaly would because you have it heatsinked, (presuming you want to test heatsinks). The wattage is how much it can dissapate on its own.

5. ### 1-Man-ArmyWhat's a Dremel?

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ok...so if i get a 10-25w resistor, how am i gonna control the current or voltage to get xxxwatts.... thats gonna be the hard part. btw wouldnt that resistor die from over voltage and current? lol as long as it wont get really hot it should be fine right?

6. ### whypick1The über-Pick

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Looks like someone needs a lesson in Ohm's Law. This is one of the basic, underlying prinicipals of electronics, and it's only 4 characters long:

V=IR

Voltage equals Current times Resistance.

With this setup, only one resistor and a voltage source, the value of the resistor determines the current drawn. So a 1 ohm resistor, with an input voltage of 1V will draw 1A of current (1 Volt = 1 Amp * 1 Ohm). If the input voltage were increased to 5v, then the current drawn would be 5A.

As for the wattage of the resistor, that's simply another part of Ohm's Law (I don't know if it's official or not, but what the hey?)

P=IV

Power equals Current times Voltage.

So, in our 1/1/1 example, the watts dissipated by the resistor is simply 1W. In the 5/1/1 example, the watts dissipated is 5W.

For your setup, I think it'd be infinitely easier to control the input voltage, as constant current sources might be over your head, and rheostats that are higher than 10W are EXPENSIVE with a capital EXPENSIVE. Some of the other guys around here probably know control setups for such high-power operations better than I do, so I'll let them chime in.

7. ### 1-Man-ArmyWhat's a Dremel?

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ok cool that kinda clears sum things up.....should i use resistors that look like this its in the last pic http://www.tomshardware.com/howto/20021021/powersupplies-03.html
since there flat surfaced...

8. ### ConKbot of DoomMinimodder

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OK I have a little more time to explain better what you need.

A variac is a variable AC transformer you can usualy go from (in the us)30Vac-180Vac. It will be expensive bu you can use it to control the speed/birghtness of pretty much any AC item. Get a true RMS digital multi-meter to measure the voltage and V^2/Z =W (voltage squared divided by impedance = wattage)

I wouldn't use resistors like those because they have the heatsinking on the side. I would use some of the TO220 resistors*link* I would lap the tab to make it flat, mount it to your dummy die with thermal epoxy, and put a ton of insulation on every part except the part of the die that the heatsink is supposed to touch.

The resistor won't burn out if you keep it from getting to hot. You could use a temperature sensing circuit to shut if down if it exceed say 100C (I don't think any dies will run that hot any time soon) Or you might find a thermal circuit breaker that will work also.

I would get the variac first, and let the voltage range on that determine which resistor you use.

Hopefully this helps out.

EDIT: You might be able to use a lighting dimmer, or a PWM setup. I would check out the dimmer as they are cheaper than a good variac. Just watch the capacity of them though, make sure it can handle what you want to go up to.

Last edited: 25 Aug 2004
9. ### 1-Man-ArmyWhat's a Dremel?

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thx for the info this gives me a better idea off what i need, to build this circuit

10. ### cpemmaEcky thump

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CBOD's right, using a meaty triac on an AC supply would probably be the best low-cost solution, a 400W lighting dimmer for example. However, this is messing with mains voltages, not good for noobs. A PWM circuit running off a 12V car battery would be a safe option, only burns to worry about.

11. ### 1-Man-ArmyWhat's a Dremel?

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lol thx for the thought off saftey first im gonna see what parts i can get before i start building this thing.

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