Electronic Circuits and Projects Forum

So i was going to use a voltage cuttoff like this to power a relay


how ever i was not thrilled about the current draw across the relay, so i found that you could use a IRF4905 to make a solid state high side switch no draw .... so i drew this up
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now i was drawing up my board so i could etch it and it hit me, can the PCB handle the draw im putting through it? the mosfet is rated to 5-10A (total as drawn 10-20A). the battery is 2.3A @ 12V(i know its over rated its an idea right now) now if i were to apply that load to it would the etched board take it with out acting like a fuse and burning up?

PCB Trace Calculator v2.0
Try this.

Ahhh, so no it wouldn't! I'm glad I asked. I'll revise my idea and use the relay with a remote to my pcb to turn it on

Use 2 ounce copper helps. Also you can remove the solder mask over the high current traces, then add a heavy layer of solder on the traces.

Got any solder wick, solder to the current traces, the IRF4905s I'm using are good for 74 amps and I know for sure I've pushed 50 through them, heat sinked of course.
Kinarfi

Originally Posted by kinarfi

Got any solder wick, solder to the current traces, the IRF4905s I'm using are good for 74 amps and I know for sure I've pushed 50 through them, heat sinked of course.
Kinarfi

good idea.that would add quite a bit of surface area

ahhh another good idea Boncuk, copper trace. now it seems like the next thing undersized would be the leads coming off the Mosfets. i know they are rated for it, but it just seems to me that there has to be a better solution to my problem. i mean so far i need omething that has the ability of a high amp relay, but does not require a substantial draw

Just back up the traces to and from the FETs and don't sweat the size of the leads, I did for a while and finally got over it, on the spec sheet for the IRF2805, I read an interesting spec, it basically said the silicone could handle 175 amps but the case could only handle 75 amps. I agree that the leads look to small for very much current, but I'm sure the manufacturers have already covered this. Don't sweat the little stuff, the IRF4905 will handle your 50 amps draw if heat sinked.
Kinarfi

Have you ever seen this style of Mosfet; http://www.st.com/stonline/products/.../ste53nc50.pdf