Is there an easy way to 'soft start' a standard mag switch?

For my ROP high Mag 2D I am powering it from 2 x KD 32600 cells, but unlike my ROP Low I cannot use my protected cells. The protection circuit will easily handle the amperage of the bulb in use, but not the inrush current on startup.

Is there an easy mod to fix this? I don't want to spend much and I don't want to put a lot of effort in, if it is too hard then I'll just use the unprotected cells and leave the protected ones for my ROP low and my lower powered light with the AW soft start. But I do have several sets of protected 32600 cells and I really do like my little 2D with the ROP high and FM deep reflector. It is a great light with lots of output and ~1 hour run time.

easiest mod isn't really a mod. just double or triple click it and the filament should begin to heat up and eventually will develop enough resistance not to activate the protection circuit

khoalie said:

easiest mod isn't really a mod. just double or triple click it and the filament should begin to heat up and eventually will develop enough resistance not to activate the protection circuit

Click to expand...

No matter how fast I click the protection circuit is so fast it doesn't allow any noticeable heating of the filament. If I loosen off the tail cap and fiddle with something that isn't a great conductor in the gap for a minute or 2 then I can eventually get the bulb to light, I can then turn it off and back on easily and it runs great - but it needs a lot of playing around to get it going the first time and that isn't really practical.

I haven't done any resistance mods but still just too much current flows with a cold filament and 80 clicking the switch gives me no better results than single, double or triple clicking.

An NTC might do the trick. You can't use the forum search on this one (not enough letters). But the Google Search of CPF brings up a bunch. Here's a few I bookmarked: NTC soft start cures 5761 and Using an NTC. The Ametherm SL12-1R010 mentioned in both posts starts out at 1.0 ohm @ 25°C and drops down to 27 milliohms at a max power rating of 10 amps. At 50% or the ROP range it is 60 milliohms. That might give you just enough to not trip the protection circuit and in the bargain extend your bulb life.

If you don't anticipate using the light in cold weather, then the NTC thermistor approach can work. But if the light might be a car light, for example, and you live in snow country, the Ametherm SL12-1R010 could have a resistance of around 4 ohms or so when cold. That might make for a very slow soft start.

In any case, you could wire the NTC thermistor into the tailcap as shown below (I actually have a voltage drop resistor installed in this photo, not an NTC thermistor, but the concept is the same). Solder the NTC to the bottom end of the tail spring. Connect a wire in series to the NTC. Drill a small hole through an insulating board (I used the lens from a AA Mini Mag) and insert your wire through the hole. Solder the wire up to a Batt- contact (I used a piece of copper that I cut and dimpled). Mount the Batt- contact on the insulating board. Glue the Batt- contact to the board and the board to the tail spring to hold everything into place.

yes there is, ntp, aka inrush current limiters, i installed one, and it did work, before protection would trip and i wasn't able to turn light on, after 0.90c part installed in series with bulb, it lights up nice and soft.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=570-1077-ND

turning off is a different story, my 32650 protected would trip protection after light was turned off, and i wasn't able to turn it back on, at first i thought it was spike during off, but it would light up right after i shut it off, was it shitty protection circuit to blame, idk, i never figured it out, i just stopped using those cells, and moved them to led light. but funny thing is everything worked great when i tested the whole thing out of the light, it is when it was all assembled i had those problems. neither i had those problems when i used them cells in the light that had aw soft start.

Al Combs said:

An NTC might do the trick. The Ametherm SL12-1R010 mentioned in both posts starts out at 1.0 ohm @ 25°C and drops down to 27 milliohms at a max power rating of 10 amps.

Click to expand...

Reading this I started thinking about the easiest way to integrate one into my light, I was thinking about in the tail cap.

Then I refreshed the page and read this:

Justin Case said:

In any case, you could wire the NTC thermistor into the tailcap as shown below

Click to expand...

This doesn't look that hard to do. I might look into getting some NTC thermistors and creating a soft start tailcap or two. Then I can save my unprotected cells for my high current bulb which has a more advanced switch with low voltage cut-out anyway - this will give me 2 sets of batteries for that light and more than 2 sets for my ROP High.

Mounting the NTC thermistor in the tailcap is fairly straightforward. In the photo I linked, I also de-anodized the D Mag tailcap because I needed room to fit 3xIMR26500 in a 2D Mag.

I also forgot one step. When you solder the wire to the underside of the Batt- contact, you probably will have a solder blob at the connection point that will prevent the Batt- contact from sitting flat/flush on the insulating board. What I did was to countersink the wire feed hole to provide room for the solder blob. Also try to make as clean of a solder connection as you can to minimize the size of the connection point.

Justin Case said:

Mounting the NTC thermistor in the tailcap is fairly straightforward. In the photo I linked, I also de-anodized the D Mag tailcap because I needed room to fit 3xIMR26500 in a 2D Mag.

Click to expand...

I also have at least one tailcap that is de-anodized because those longer protected D cells are a tight squeeze otherwise. I think I'll be able to work out how to wire up the NTC tailcap mod without too much trouble.

I don't think I'll bother with this for the ROP Low bulbs though, not enough advantage and with less amps flowing there would be more resistance from the NTC thermistor - my low bulbs are lasting just fine as they are and the protected cells handle the inrush current every time.
The 3853 high also seems to be OK with the protected cells and is also less likely to blow than the 3854 so no mod needed their either.
My Bi-pin bulbs are used with soft start switches (2 x AW and 2 x Alan B) so they are fine.

It looks like this solution is only really needed on one light - my 3854-H, but I really like this light. It has really good output in terms of brightness and colour and the deep reflector gives it a good looking (smooth) beam with decent throw. I only have 7 unprotected 32600 cells, so if I use 2 in my ROP high light then I don't have a spare set for my 3D - this matters because my 3D is a great light that I like to use a lot due to the great UI on the Alan B driver and the output from the Svetila 64430 bulb at 10V. My 3D is a great flooder and my 2D ROP high is a great thrower, I also like my 2D ROP low as a great thrower (also deep reflector) with about twice the runtime of the high bulb (giving around 2 hours from 2 x 32600 cells).

Maglite - my favourite brand of flashlight hosts.

Justin, I seen that picture in another thread, I believe you said you were using it in a Mag85 with 3x26500s. I have this same setup and was just wondering what type of resistor you used for this build? Ive used the Ametherm before but they do seem a little slower.

Good memory. Yes, I was blowing WA1185s in a Mag85 build driven by 3xIMR26500.

I used an 0.15 ohm, 1% Vishay-Dale resistor from Digikey, and that cured the instaflashing. The hookup wire is 22 ga Teflon jacketed, stranded wire.

Happen to have a link to it/part number, or maybe a spare lying around? I need to make myself one, just popped a fresh 1185 last night.

I might have a spare. I have to check on Monday. If I have one, I'll send it to you. Let me check Digikey's web site later for the specific item and its link.

With an inductor and a schottky diode you can make a softstart circuit.

Just connect the diode antiparallel to the inductor.
When switched on the inductor let's the current rise up "slowly" and when switched off the diode prevents the voltage spike from the inductor.

Der Wichtel said:

With an inductor and a schottky diode you can make a softstart circuit.

Just connect the diode antiparallel to the inductor.
When switched on the inductor let's the current rise up "slowly" and when switched off the diode prevents the voltage spike from the inductor.

Click to expand...

:thumbsup: brilliant,
thanks. exactly what i needed.

now what is indicator, ???

Justin Case said:

I might have a spare. I have to check on Monday. If I have one, I'll send it to you. Let me check Digikey's web site later for the specific item and its link.

Click to expand...

Thanks a million! Me and my 1185's thank you. :thumbsup:

I ordered Digikey P/N RSB-.15RCT-ND, which is a Vishay 0.15 ohm, +/-1%, 3W silicone, through-hole resistor. I also have RSB-.10RCT-ND, which is 0.10 ohm. Send a PM to me with your mailing address and I'll send one of each out to you.

Sounds good Justin, thanks again. PM sent :thumbsup:

alpg88 said:

:thumbsup: brilliant,
thanks. exactly what i needed.

now what is indicator, ???

Click to expand...

An inductor is a low-pass filter, a component that takes advantage of electromagnetic fields to alter the signal passing through them. They can be thought of as kind of the capacitor's evil twin.

Chrontius said:

An inductor is a low-pass filter, a component that takes advantage of electromagnetic fields to alter the signal passing through them. They can be thought of as kind of the capacitor's evil twin.

Click to expand...

lol, thanks,
my fault, i missread the word, i read it as indicator, not inductor, i know what those are. thanks again.