Cyrix Hotplate Howto

fimbulvetr writes "Looking to put those old processors to work? Tired of catching flack for having hardware, but no use for it? Worry no more! Doc from rabidhardware.com shows us how to employ 7 Cyrix processors to build a spectacular cooking device. Cooking instructions not included. Void where prohibited."

Comments

Re:or

[FidelCatsro]

sorry about that formated the link badly http://www.rabidhardware.net.nyud.net:8090/index.p hp?id=44

Mirror

[SmokeHalo]

Here is a mirror, as I have found the site to be /.'d already.

Google Mirror Site Available

[ramsesit]

Google Mirror also available

http://www.google.com/search?q=cache:N6NjjllZah8J: www.rabidhardware.net/index.php%3Fid%3D44+&hl=en

Re:I call shenanigans!

[Technician]

My guess is that he didn't REALLY get 120 watts through, but enough current to warm up the chips nicely.

From a quick Google search on one of these...

USM 7805 is a 3-terminal positive voltage regulator designed with built in internal current limiting, thermal shutdown and safe-area compensation for maximum flexibility and safety . With adequate heat sinking provided, USM 7805 can deliver up to 1.5A output current.

I'm with you on your conclusion. The chip at current limiting gives you about 7.5 Watts, not 120 Watts or anything close. I have a night light for the kids that put out the same heat he could have gotten.

Re:I call shenanigans!

[YankeeInExile]

Well, let me backpedal a bit on my flat denial.

I can imagine designing a system that used a 20W heater to heat a very large mass of metal to a suitable temperature to fry an egg, with sufficient heat capacity to keep that temperature throughout the cooking of the egg

Now, assume a mass of copper (Specific Heat of 0.385 Joule/g/C)

I just fried an egg, using my little hotplate. I used a deep-fry thermometer to measure the temperature of the oil at 135C near the middle of the cooking process (just before I turned the egg). From raw egg to breakfast was 3 minutes 30 seconds (plus or minus 15 ... It's difficult to juggle an egg a hotplate a fry pan and a stopwatch without setting the kitchen on fire!)

So, I soaked 850 (power output of hot plate) watts into my breakfast for 210 seconds, or a total energy input of 178.5 kJ. So, how much copper do I need to heat to a 135, such that after sucking out 175,000 joules it will be about 120. Fifteen degree drop , 175000 joules, comes to about 30 kg of copper.

To heat 30 kg of copper to that 135 in the first place (from an ambient of, let's say 25) will take 110 * 30000 * 38.5 equals 1.27 MJ.

At twenty watts, a mere 17.6 hours, assuming your heater and the block of copper are in a perfectly insulated space. Putting it in the real world will make it take longer (in fact, probably an infinite amount of time because of radiation loss).

Learn the difference between heat and temperature