Switches for high currents

Flashlight Modding and DIY Parts
21

Nope, depend on area of switch contact not watt rate :wink:

22

will post here FET switch that operated from 3V coin cell

give me an hour

23

here it…

for FET, use IRF7811, Si4404 etc. those come from SO8 package.

24

IRF7811 has 15mOhm Rds-ON for 3V Vgs, 9A Drain

so, 8A drive current it will drop 0.12V

25

Thank you guys!
Nice clearly depicted circuit, Pavithra. Found this IRF7811 datasheet for download. The fets dimensions are only 1.75x5.0x6.2 mm, really small. Should find space beside a coincell in a tailcap…

26

Works fine but according to the EE’s there is some leakage current. The best description is posted here by Oldlumens and Techjunkie.

27

What I would like to find are the smallest possible switches to handle about 5A, it might be my poor english but I do not find much info about them.

I want it for a mod on an e-cig that uses IMR batteries, the problem with the fet ones is the switch is to be used many times per day, so the coin battery will not last that much.

28

Thank you Pavithra for your support. I finally finished my diy FET-switch for my l2p and it works great. It was a challenge to solder this tiny piece, especially the GATE-pin, without frying it. You have to do it quick with a hot iron. The switch is 5mm larger now and the tailcap cannot be screwed flush. Maybe i will fill the gap with an l2t-style rubber or something or i will shorten the thread of the body to fit proper.

29

Can you show me some picutures and kind of walk me through this, I’m really bad at reading diagrams and I want to build the same thing.

30

sorry to bring up a old thread, but would a tip120 or other similar transistor work for use in a light that is only running about 1 amp but requires a electronic switch?

or 2Nxxxx transistors?

31

Pok, if still here, can you elaborate on what’s posted above about switch rating?

I find I have Omten PBS101C mentioned there, marked “1.5A 250V” (rounded corners)
and
Omten PBS101, also marked “1.5A 250V” (bigger, thicker, square corners)

I’ve never pushed a flashlight past something less than 2A, and don’t use more than single cell lights.
But

I have this LD-1 that can go to 5A in my “got to learn how to use this” stack.

So — above Pok mentions what matters is the size of the switch contacts.
That’s inside the black box, right?

So — general question this thread started with — please say more about high power switches? What’s out there, what handles what?