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Transistor Switch

Posted: Mon Jul 19, 2010 1:59 pm
by mrdobolina
I can't remember where i saw it, but it was a pic of a 2pdt switch used to change between to resistors. I believe it had C and E on the poles and the bases soldered together? Does this work?

I was planning on using a 3pdt, tran on each side...wires on the middle poles.

Just wondering...thanks in advance.


Dobo

Re: Transistor Switch

Posted: Mon Jul 19, 2010 11:44 pm
by floating opera
coolest username handle EVER !!!

:omg: :joy: :omg:

Re: Transistor Switch

Posted: Tue Jul 20, 2010 4:01 am
by McSpunckle
You've got it right. The 3PDT switch is a cleaner way, though.

I have to ask, are you flipping a transistor, or actually switching between entirely different transistors? If you're just flipping one, there's a better way.

Re: Transistor Switch

Posted: Tue Jul 20, 2010 8:27 am
by mrdobolina
interesting....this is a DeviEver SM. I was just going to flip it for the SM/VFM.

What is the other method? perhaps I can do both and have a SM/VFM/GZ?

Thanks for the help.


Dobo

Re: Transistor Switch

Posted: Tue Jul 20, 2010 9:34 am
by McSpunckle
Basically, the commons of the switch are connected to the collector and emitter of the transistor. Make an X accross the other terminals. I usually slide a component lead or piece of solid wire through one set of terminals, and set a piece of wire/lead on top of the other set (so one's on top and one's on bottom). Run a wire directly off the base of the transistor's base, and the two other wires from two side-by-side terminals of the switch.

...this is actually sort of difficult in text.

I posted a picture of a Godzilla that had the mod done in the guts thread in gear... but I think maybe I should make you a diagram. Hah.

Re: Transistor Switch

Posted: Tue Jul 20, 2010 9:53 am
by McSpunckle
Ok, here ya go.

Remember on the X to make sure the two wires don't touch.


The easiest way to mount the transistor (that I've found) is to hang it off the side of the switch. There's just barely enough lead to get to the common lugs of the switch. Once they're soldered, use a probe or screwdriver to pull the leads away from the other lugs.

Then, wrap some wire around the lead for the base and solder it on there. This is a -great- time for some heat shrink, but if you're careful, you can get away without it.

Re: Transistor Switch

Posted: Tue Jul 20, 2010 10:54 am
by mrdobolina
Wow, Eureka!

Makes perfect sense. thanks!


Dobo