Modifying Mag switch? (for Mag85 and Mag623)

I'm building a Mag85 (Mag 3C) and a Mag623 (Mag 2D).

I'm planning to use these with the KIU High temp socket kits.

Besides installing the KIU, Do I have to do some modding to the switch?
Any pictures available on what should be done?

Bypass the switch with a low on-resistance n-type mosfet: connect battery minus to the mosfet source, bulb minus to the drain and the use the std switch to pull the mosfet gate to battery plus voltage level.

Remember to connect some generic pull-down resistor between mosfet gate and source, otherwise your flashlight will turn off extremely s-l-o-w-l-y... Not that I would have ever, never driven a mosfet gate without a pull-down resistor!

-N

Here is a thread detailing this mod. This thread shows the idea of the spring mod for lower resistance, though many add solder.

Nereus nice mods, shows high degree of electronic knowledge.

I'd just like to understand this mosfet. Is there a drawing somewhere?

Jim

Nereus said:

Bypass the switch with a low on-resistance n-type mosfet: connect battery minus to the mosfet source, bulb minus to the drain and the use the std switch to pull the mosfet gate to battery plus voltage level.

Remember to connect some generic pull-down resistor between mosfet gate and source, otherwise your flashlight will turn off extremely s-l-o-w-l-y...

Not that I would have ever, never driven a mosfet gate without a pull-down resistor!

-N

Click to expand...

Jimjones3630, you can find general information about mosfets here and here.

I have used this technique with other than hotwire mods, but after having a quick look on the specs of the bulbs you are going to use I think for example IRF1704 mosfet should suit your needs. You can find the IRF1704 datasheet here.

You may find this thread informative too.

-N

Mosfet has three leads one goes to bat. the other to light and third is ground probably? Is that about right? Thanks Jim

jimjones3630 said:

Mosfet has three leads one goes to bat. the other to light and third is ground probably? Is that about right? Thanks Jim

Click to expand...

The third one, the gate, is used to control the mosfet on/off state. If you connect it to the battery plus, the mosfet is turned on. Leaving it disconnected will turn the mosfet off... and remember to use the pull-down resistor between mosfet gate and source. But othwerwise you have it correct: connect (n-type) mosfet source to the battery minus and drain to the bulb minus.

-N

Hey thanks for the help, one last question if you don't mind. Pull-down resistor, do you have a web link or parts number??

jimjones3630 said:

Hey thanks for the help, one last question if you don't mind. Pull-down resistor, do you have a web link or parts number??

Click to expand...

Any 8-10K 1/8-1/4 Watt resistor will do.

P.S. I like this mod. I might just switch (no pun intended) all my lights to this.

Thanks. Radio shack probable will have it? If sounds dumb I just learned to solder.

The upside is teach a hungry man to fish and he can feed himself, give him a fish and he's just dependant on you.

jimjones3630 said:

Thanks. Radio shack probable will have it?

Click to expand...

Absolutely.

Search around here. There's an AWESOME tutorial on soldering. MAybe someone can help with a link.

JimmyM said:

Search around here. There's an AWESOME tutorial on soldering. MAybe someone can help with a link.

Click to expand...

Is this thread what you had in mind: https://www.candlepowerforums.com/threads/141539

Thanks for the help guys.

The link that Mudman gave was good, but this is only when the switch stock.
But now as I'm going to mod the switch with the KIU socket so:
C- Mag http://kiu01139.host.sk/magc/index.htm

D - Mag http://kiu01139.host.sk/2.htm

The case is different I suppose.

So if I only follow these instructions (KIU links above) is it do I have a danger that something would melt or fail otherwise?

The idea Nereus gave sounds good, but maybe out of my ball park...

JimmyM said:

Any 8-10K 1/8-1/4 Watt resistor will do.

P.S. I like this mod. I might just switch (no pun intended) all my lights to this.

Click to expand...

Yes this is a great mod. I've done the soldering practice, and read much about the Mosfet for a soft start, which with the right bulbs&bat. combo will not need regulation,hotdriver, and save some $$.

I've got some Mosfet ordered, will find some resistors and go to play>

Here's an interesting link on Mosfet

http://candlepowerforums.com/vb/showthread.php?t=8682

Nereus said:

I think for example IRF1704 mosfet should suit your needs. You can find the IRF1704 datasheet here.

-N

Click to expand...

Hello again,

Places I looked IRF1704 are out of stock. Do you think a
IRL3713PBF http://www.irf.com/product-info/datasheets/data/irl3713pbf.pdf

or
IRFB3207PBF http://www.irf.com/product-info/datasheets/data/irf3703pbf.pdf

would do? The IRL3713PBF is more expensive. I don't know enough to know why it is and if it is worth it?

Thanks Jim

I had quick look on the IRL3713PbF characteristics that are crucial for your application (mag85 and mag623):

- Max drain-source voltage 30V -> ok

- Max continuous drain current 180 amps @ 100C -> ok

- Max peak pulse drain current 1040 amps -> ok... actually more than ok...

- Max gate-source voltage 20v -> ok

Furthermore, operational temperature limits (although narrower than that of IRF1704) should tolerate the heat coming from the bulb and allow the use of the flashlight in winter. The on-state resistance is also low enough and achieved at relatively low gate-source voltage so there should not be excessive power dissipation and heating in the mosfet.

To sum up, I think IRL3713PbF should work nicely in your mod - in some aspects (e.g. great dynamic characteristics) it is *way* overkill but that is not a problem. And please remember that I have no experience on that specific mosfet and I have very little experience about hotwire mods...

...and now excuse me, I have to leave because it is 10:00 AM and my labrador retriever stares at me intensively from a distance of one meter and clearly *demands* getting out for a walk... and during 3,5 years I have learned NOT to ignore that intense staring... Have to comment the other component later.

-N

Hey, nice looking lab. I understand the consequences of ignoring...wish could figure out how to post pics here. I would show you my 2 1/2 year old black Lab with her constant companion a 3 1/2 year old Great Dane.

Will try that Mosfet then as I got the parts # from another post here. Plan to use this for Orsam 100w, 12v, and 250w, 24v mods.

Look forward to seeing what you think about that, and yes from looking at your list of mods and the amount of electronics in each I can tell you don't have much experience.

Jim

mudman cj said:

Here is a thread detailing this mod. This thread shows the idea of the spring mod for lower resistance, though many add solder.

Click to expand...

I modded my spring with 10gauge wire. :lolsign: Made a big improvement to its ouput and color temp.

The 10 ga wire you mentioned, is that solder wick in that link pic?

lasercrazy said:

I modded my spring with 10gauge wire. :lolsign: Made a big improvement to its ouput and color temp.

Click to expand...

IMO, IRL3713PbF should be able to handle 250W bulbs too. However, the 24 V battery voltage exceeds the max gate-source voltage so I suggest that you use e.g. voltage divider to drop the gate drive voltage. When it comes to another mosfet, you mention IRFB3207PBF in the text but there is a link to IRF3703PBF datasheet - which one are you going to use?

Here is guidance how to post pics.

-N