hi all i'd like to dimm a powerfull halogen lamp of about 100Watt and 12v DC supply.
what kind of mosfet do you suggest? i tried with an irf520 but with a 20watt 12v dc lamp it did not go to zero (the lamp was a little lighted up) and when i tried to ad another 20 watt lamp they never lighted up at highest level (the current seemed to be divided between the 2 lamps).
thank you
giorgio
ps sorry for my english!!
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hmm... I wonder if this is more a problem with your PWM control instead of your FET. you might need a low pass filter after the FET. But first do you have a wiring schematic of how you are hooking up the dimmer?
The IRF520 is going to have many problems. First, it is not a "logic-level" MOSFET so it needs about 10V at the gate to turn on -- your board is only putting out 5V max. And even if you did turn it on, its on-resistance is (worst-case) 0.27 ohms meaning at 100W/12V (i.e., lamp current is 8.3A) it will dissipate 18W!!! You may need a fire extinguisher.
This site has an example circuit -- scroll down until you see the NDP6060L. With a slightly better MOSFET (lower Rds(on)) or just a little bit of heatsinking it should do the trick at 8.3A.