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Registered Member #4266
Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874
Hi I was playing around with the wiring of the circuit I built, and I smelled the magic smoke. I've replaced the 555 and the hex inverter, and the power supply tests ok. I was wondering if the below picture, there is anything wrong with the wiring, It shows 12volt from the multimeter with the setting ac ,it is connected to the two alligator clips, so I think the 555 is working, but no current is going through.
I connected a 12 volt positive source to the emitter when I smelled the smoke.
Registered Member #580
Joined: Mon Mar 12 2007, 03:17PM
Location: Melbourne, Australia
Posts: 410
We can not work out anything from your poor angle low res pic, please take several high resolution photos from various angles, in a well lit environment, and LINK to them here (use the attachments thread, or other hosting service), as to not exceed the maximum picture width rule. Also please let us know the inverter and mosfet part numbers.
If you have a schematic of what you are actually attempting to do, this would also help.
Registered Member #4266
Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874
I followed the article and simulated it, across the FET its showing a square wave. Building it thought the nichrome wire doesn't heat up, were the first xmm2 is. Its showing 5volt on were xmm2 is.
Registered Member #4266
Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874
yep the simulator is showing 89amps and 144mVolt, the below picture is the setup. I tried connect positive 12volt to the middle of a hbridge setup when I smelled smoke, if theirs nothing wrong with the circuit I'll get a replace FET.
Registered Member #19
Joined: Thu Feb 02 2006, 03:19PM
Location: Jacksonville, FL
Posts: 168
What is the impedance of XMM2? Or rather what is it? Take a look at the Datasheet. This FET is rated for 130W, actually IR recommends 50W in the TO220 package which is what you have.
You need a good heat sink! especially if you want to pass any real power through it! Without doing any math I would say you can only send maybe 2A through that package without over heating it. Transistor packages are not really designed to cool the chip but rather transfer as much heat as possible to a heat sink.
Registered Member #4266
Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874
It was a 3amp source, so probable fried them :( , I've ordered some more and will try the circuit out, the circuit looks like it would work, but then its not my area. I've order some heat sinks as well, which should handle the power.
Registered Member #4266
Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874
The mosfet were fried, but I think I allso missed up the 555, found a link that has help some, I had a cap instead of a wire, and maybe the reset pin wasn't connected.
During simulator the fet doesn't work, and the same in reallife, so I think something else is wrong...
Tried this circuit , and are getting 1volt across xmm1, now I'm really lost...Reading 0.4volt give or take, at 12volt source and 4mohm fet its probable ok, with some of the fets, the old ones, 7-5volt, the only think I can think off is I had a pull up resistor(what does that mean, will google).
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Maybe dead mosfet
