Light dimmer

The topology is right but I think your MOSFETs are under rated. You want something more like a RFP50N06 with an RDS(on) of 0.022.

The steady state current is somewhere above 4A each. The power lost in the resistance is I^2R. For the 0.122 Ohm MOSFET this is a couple of watts. This means you do need some real heat sinking in that case. With the lower value, the case should be enough surface area.

#291606 **

On Jan 24, 11:56=A0am, Yvan wrote:

#291606 **

This should do the trick.Taken from the link you provided , just changed slightly to suit your needs(hopefully :0) ) View in LTSpice. If you don't have a copy , get one from Linear's website.Fantastic for newbies and professionals. Made with parts supplied with the program , so you should'nt have to find subccts on the net. FET(p channel) does not have to be the one specified , as long as it can handle the current and any voltage that it may see. The lower the on resistance the better , but this watch the gate charge. At this frequency though , it's probably not to much of an issue. R2 and R3 would obviously be a pot in real life , I'm just not sure if LTSpice comes with a pot subcct. D1 is just a protection diode for any inductive spikes that may crop up. Use a 1n4007 or such like.

Cheers Rob

copy and paste into notepad , and rename to file.asc

Version 4 SHEET 1 1412 680 WIRE -96 -80 -256 -80 WIRE 224 -80 -96 -80 WIRE 928 -80 224 -80 WIRE 1136 -80 928 -80 WIRE 1216 -80 1136 -80 WIRE 928 -48 928 -80 WIRE 1216 -48 1216 -80 WIRE 272 -32 -144 -32 WIRE 1136 16 1136 0 WIRE 1136 16 1104 16 WIRE 1136 32 1136 16 WIRE 1216 32 1216 16 WIRE 1216 32 1136 32 WIRE -256 48 -256 -80 WIRE -32 64 -64 64 WIRE 224 64 224 -80 WIRE 224 64 192 64 WIRE 640 96 560 96 WIRE 928 96 928 32 WIRE 1056 96 928 96 WIRE 640 112 640 96 WIRE -144 128 -144 -32 WIRE -32 128 -144 128 WIRE 496 144 448 144 WIRE 560 144 560 96 WIRE 928 144 928 96 WIRE -32 192 -128 192 WIRE 272 192 272 -32 WIRE 272 192 192 192 WIRE 288 192 272 192 WIRE 320 192 288 192 WIRE 448 192 448 144 WIRE 448 192 400 192 WIRE 768 192 640 192 WIRE 784 192 768 192 WIRE 640 208 640 192 WIRE 448 240 448 192 WIRE 496 240 448 240 WIRE 576 240 560 240 WIRE 1104 240 1104 112 WIRE 1104 240 928 240 WIRE -96 256 -96 -80 WIRE -32 256 -96 256 WIRE 288 272 288 192 WIRE 928 272 928 240 WIRE 576 304 576 240 WIRE 640 304 640 288 WIRE 640 304 576 304 WIRE -256 336 -256 128 WIRE 64 336 -256 336 WIRE 288 336 64 336 WIRE 64 352 64 336 WIRE -128 464 -128 192 WIRE 768 464 768 192 WIRE 768 464 -128 464 FLAG 64 352 0 FLAG -64 64 0 FLAG 928 272 0 SYMBOL res 416 176 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R1 SYMATTR Value 500 SYMBOL Misc\\NE555 80 160 R0 SYMATTR InstName U2 SYMBOL voltage -256 32 R0 SYMATTR InstName V1 SYMATTR Value 12 SYMBOL diode 496 256 R270 WINDOW 0 32 32 VTop 0 WINDOW 3 0 32 VBottom 0 SYMATTR InstName D2 SYMATTR Value 1N4148 SYMBOL cap 272 272 R0 SYMATTR InstName C1 SYMATTR Value 100n SYMBOL diode 560 128 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName D3 SYMATTR Value 1N4148 SYMBOL res 624 96 R0 SYMATTR InstName R2 SYMATTR Value 22k SYMBOL res 624 192 R0 SYMATTR InstName R3 SYMATTR Value 22k SYMBOL res 912 -64 R0 SYMATTR InstName R4 SYMATTR Value 1k SYMBOL pnp 864 240 M180 SYMATTR InstName Q1 SYMATTR Value 2N2907 SYMBOL res 880 176 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R5 SYMATTR Value 220 SYMBOL nmos 1056 16 R0 SYMATTR InstName M1 SYMATTR Value IRF6618 SYMBOL res 1120 -96 R0 SYMATTR InstName R6 SYMATTR Value 1 SYMBOL schottky 1232 16 R180 WINDOW 0 -41 23 Left 0 WINDOW 3 -176 58 Left 0 SYMATTR InstName D1 SYMATTR Value PMEG4010BEA SYMATTR Description Diode SYMATTR Type diode TEXT -290 470 Left 0 !.tran 100m

sa #291606 **

Here is a NMOS version ;0)

Version 4 SHEET 1 1412 680 WIRE -96 -80 -256 -80 WIRE 224 -80 -96 -80 WIRE 944 -80 224 -80 WIRE 1024 -80 944 -80 WIRE 272 -32 -144 -32 WIRE 944 -32 944 -80 WIRE 1024 16 1024 -80 WIRE -256 48 -256 -80 WIRE -32 64 -64 64 WIRE 224 64 224 -80 WIRE 224 64 192 64 WIRE 640 96 560 96 WIRE 944 96 944 48 WIRE 976 96 976 32 WIRE 976 96 944 96 WIRE 640 112 640 96 WIRE -144 128 -144 -32 WIRE -32 128 -144 128 WIRE 1024 128 1024 112 WIRE 1120 128 1024 128 WIRE 496 144 448 144 WIRE 560 144 560 96 WIRE 1024 144 1024 128 WIRE 1120 144 1120 128 WIRE -32 192 -128 192 WIRE 272 192 272 -32 WIRE 272 192 192 192 WIRE 288 192 272 192 WIRE 320 192 288 192 WIRE 448 192 448 144 WIRE 448 192 400 192 WIRE 768 192 640 192 WIRE 784 192 768 192 WIRE 944 192 944 96 WIRE 944 192 864 192 WIRE 640 208 640 192 WIRE 1024 224 928 224 WIRE 1120 224 1120 208 WIRE 1120 224 1024 224 WIRE 448 240 448 192 WIRE 496 240 448 240 WIRE 576 240 560 240 WIRE -96 256 -96 -80 WIRE -32 256 -96 256 WIRE 288 272 288 192 WIRE 928 272 928 224 WIRE 576 304 576 240 WIRE 640 304 640 288 WIRE 640 304 576 304 WIRE -256 336 -256 128 WIRE 64 336 -256 336 WIRE 288 336 64 336 WIRE 64 352 64 336 WIRE -128 464 -128 192 WIRE 768 464 768 192 WIRE 768 464 -128 464 FLAG 64 352 0 FLAG -64 64 0 FLAG 928 272 0 SYMBOL res 416 176 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R1 SYMATTR Value 500 SYMBOL Misc\\NE555 80 160 R0 SYMATTR InstName U2 SYMBOL voltage -256 32 R0 SYMATTR InstName V1 SYMATTR Value 12 SYMBOL diode 496 256 R270 WINDOW 0 32 32 VTop 0 WINDOW 3 0 32 VBottom 0 SYMATTR InstName D2 SYMATTR Value 1N4148 SYMBOL cap 272 272 R0 SYMATTR InstName C1 SYMATTR Value 100n SYMBOL diode 560 128 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName D3 SYMATTR Value 1N4148 SYMBOL res 624 96 R0 SYMATTR InstName R2 SYMATTR Value 22k SYMBOL res 624 192 R0 SYMATTR InstName R3 SYMATTR Value 22k SYMBOL res 880 176 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R5 SYMATTR Value 220 SYMBOL res 1008 128 R0 SYMATTR InstName R6 SYMATTR Value 1 SYMBOL schottky 1136 208 R180 WINDOW 0 -41 23 Left 0 WINDOW 3 -176 58 Left 0 SYMATTR InstName D1 SYMATTR Value PMEG4010BEA SYMATTR Description Diode SYMATTR Type diode SYMBOL pmos 976 112 M180 SYMATTR InstName M1 SYMATTR Value Si4425BDY SYMBOL res 928 -48 R0 WINDOW 0 53 17 Left 0 WINDOW 3 68 39 Left 0 SYMATTR InstName R4 SYMATTR Value 10k TEXT -290 470 Left 0 !.tran 100m

Thank's.

-- ___ ____ /__/ / \ ** Registrovani korisnik Linuksa #291606 ** / / \/ /\ \ ** Registered Linux user #291606 ** /__/\____/--\__\ **