D.I.Y -- Simple FET Switch KIU-D Mod -- How To Guide . PIC Heavy

petrev

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Hi

An FET Switch for reduced resistance and higher current use without damage to switch parts.

Did this once before but didn't take any guide pics ! so here is a Simple-FET-Switch How To . . .

Circuit by JimmyM [opens in New Window]



First Cut a 30mm Disc from 2 Sided Copper PCB - I used 32mm hole saw



Mark it up + These are most of the tools and parts I used
(little DPAK is for reference - Used the bigger D2PAK F2804L for upto 40V)
4.7K Resistor only for Voltages ~>20+V

(JimmyM suggests a switch to 2.2k and 5k for the IRF2804 MOSFET - it will switch faster and thus reduce the heat generated during turn on and off)

Alternative MOSFETs are the 24V 1324 (?24V Ref) or if voltage won't exceed 30V the IRLR7843 (Ref.JimmyM)
or >40V with IRF3206



Dremel off the rough edges of the disk to fit and chamfer the edges so that there are no unwanted contacts.



Use the KIU-Base as a guide to drill through the mounting holes



Dremel off the rough edges round all the holes and make the hole for the Batt-Neg wire to go to the back side.



Cut the grooves to form a rudimentary circuit . . . I used the small engraving tool in the Dremel.



Prepare the surface with some Emery Paper/Wet and Dry Sandpaper/Or Similar



Mark the Through Hole position for the Source FET leg



Drilled and then cleared a non contact area on the circuit side using the engraving tool




Solder all the parts in place . . .
1. First tin the contact area for the Drain HeatSink. Then place FET in position with the Source Leg folded back through the hole and solder Drain HS.
2. Then the Gate leg is soldered down.
3. Then solder the G-S resistor in place on the Source leg
4. Then solder the G-S resistor to the Gate Pad/Area
5. Then solder the (+20Vonly) Switch-Gate resistor to the Gate Pad/Area
6. Then solder Sw-G resistor to the SW Pad/Area



Attach the Red Switch Wire (Front)
and the Brown/Black Batt-Neg Wire (Rear) and solder Source leg to back.

.

Stuff it into your KIU-Base and feed the KIU-Socket wires through the central hole



I attached some temporary pins to the Batt Neg and KIU-Pos wires, then temp. soldered the Drain-KIU wire and tested using a 3x C-Lion Mag-KIU.
I always wire my KIU-Sockets with the NEG to the Pin-Socket near the Logo and then fill the Logo in Black to remind me !



Plug together then touch the SW-Wire to the POS and :thumbsup: all OK.

That's it ! ! !

All you have to do then is fit it into a KIU modified D-Switch as before.





Assemble into D-Mag . . .
Done

Pete
 
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saeckereier

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Very nicely done, indeed!
Nice pictures and well written, won't be of any interest for myself, but I'm sure it'll be for others, thanks for the effort!
 

petrev

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Thanks, Pete. :thumbsup:

So,... if >= 10A, then do this with KIU socket.

Hi Cat

Will save wear and tear at any current but definitely required over about 10A in my opinion.
Might be useful from about 8A or lower depending on state of switch !

Caution: As JimmyM has just pointed out over in Most Powerful Thread

This won't soft-start the bulb though. It is a super low resistance switch. Damn sturdy by the look of it. But since it switches on really fast AND has low resistance, it will give the bulb a larger current spike than standard modded mag switch. It's a great idea for high current bulbs that aren't going to instaflash. Like the 64623 on 13 cells. Or the 64458 on 16-17 cells.

No SoftStart so beware of lowered resistance :poof:

Pete
 
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cat

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ok, so...
if >= 10A [and no instaflashing with existing resistance-reducing mods],
then do this with KIU socket.
...and if the quicker start pushes it into instaflashing, then...I don't know, individual choice. I'd prefer not to rely on the standard switch resistance, and the switch getting hot.

Re the ROP Hi application of this switch... I was also about to ask where you put it.
 

petrev

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ok, so...
if >= 10A [and no instaflashing with existing resistance-reducing mods],
then do this with KIU socket.
...and if the quicker start pushes it into instaflashing, then...I don't know, individual choice. I'd prefer not to rely on the standard switch resistance, and the switch getting hot.

Re the ROP Hi application of this switch... I was also about to ask where you put it.


Maybe +NTC for slower start high current apps ?

. . . or probably the best thing is going to be the JM-SST ! Second half of batch probably won't be too far down the line - I think JM is just waiting on a few parts ?

Pete
 

JimmyM

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Second half of batch probably won't be too far down the line - I think JM is just waiting on a few parts ?

Pete
How right you are.

That C switch mod used an Internation Rectifier IRLR7843 (smaller) and only one resistor since the voltage would never exceed 18V at the gate. It's a little tricky since the MOSFET has to be in the negative leg of the bulb. I had to put a washer under the focusing roller/screw to lock down the bulb slide. Otherwise contact with the metal reflector would turn the light on. So I adjusted the height of the bulb until the reflector wouldn't touch it even when screwed down all the way. Now I get just a mV or 2 drop through the whole switch. On fresh AW C Li-Ions, it's quite nice.
 

cat

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Maybe +NTC for slower start high current apps ?

. . . or probably the best thing is going to be the JM-SST

This for applications where the current is higher than the AW driver can handle?


JimmyM said:

I need to get my parts list together before these are gone. For one of the top 5 or 6 on LuxLuthor's Most Powerful Maglite Mods List
...I'm trying to sort out which is the smallest with a runtime of 20 minutes at least.
 
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JimmyM

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It's just a simpler cheaper alternative. It has just one mode and you can adjust the maximum duty cycle. It doesn't regulate.
AWs existing PWM softstarter has low-medium-high plus flashing ans is about 3 times as much.
My unit can handle up to 40 volts as it is right now. If you have needs that exceed that, let me know. Ultimately, it can handle 80V.

This for applications where the current is higher than the AW driver can handle?
I'm not sure how much current AWs can take, but this one handled 16V at 20+ amps. It's the amps that cause heat. If you have a 24V bulb running at 28V and 10-11 amps, this will run cooler and still drive a ~300W bulb. SO if we say that 20A is it's limit and it can handle 40V, I suppose that an 800W bulb is not out of the question. Not reasonable, but it shouldn't exceedc the capabilities of the driver. I welcome someone to give it a try.
 
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JimmyM

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I've got some single sided board laying around, I could just etch a batch of MOSFET switch boards that you guys can mount your own components on. I could make it suitable for both surface mount and thru-hole resistors. You would only have to supply 1 or 2 resistors and the MOSFET.
Pretty sure they'd be cheap.
I could even just send you guys a PDF file you can print on photo paper with a laser printer, iron them onto the board and etch them yourselves.
 

petrev

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This for applications where the current is higher than the AW driver can handle?
. . .
I need to get my parts list together before these are gone. For one of the top 5 or 6 on LuxLuthor's Most Powerful Maglite Mods List
...I'm trying to sort out which is the smallest with a runtime of 20 minutes at least.

Yes Cat - Get one of the JM-SSTs quick before this run goes and then sort out how to use it ( well that would be my route !)

:twothumbs

Have fun
Pete
 

cat

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I'm not sure how much current AWs can take, but this one handled 16V at 20+ amps. It's the amps that cause heat. If you have a 24V bulb running at 28V and 10-11 amps, this will run cooler and still drive a ~300W bulb. SO if we say that 20A is it's limit and it can handle 40V, I suppose that an 800W bulb is not out of the question. Not reasonable, but it shouldn't exceed the capabilities of the driver.

ok, AW D driver :
- Input voltage from 6V - 30V Max. open voltage ( Vin = Vout );
- Drive bi-pin hotwire bulbs up to 150W ( 200W intermittent use );

How does that compare? 28V, 30V, that's ok, but some of the top 5 or 6 setups in LuxLuthor's list exceed 150W. You estimate about 20A, but amps is not specified for the AW - can it be estimated from the V and the 150W limit?

[edit:] I'd guess that this setup would be able to handle more than the AW switch. I don't know what those extreme top 5/6 use - there doesn't seem to be that much detail given. I'd probably use the AW switch if I could, to avoid having to try to do the soldering. (I have a 5761 setup just waiting for the reflector to arrive from the PO, so I want to do something substantially more powerful next.)
 
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