Radio Shack 1.5/3volt to 9volt DC/DC converter

[aksim]

Part#990-0236 is this a viable alternative considering you would have to resistor down to 4 volts. I was thinking converter plus two AAA's in a 2 AA light.

 

[AlK]

A nice idea but I'm not sure how well this would work in a flashlight application. The description on the RS web page indicates a current consumption of 50 mA (i.e., on the input). Since DC-DC converters are kinda sorta like "DC transformers," you probably can't get more than 50/(9/3) ~= 15 mA out of it at a 9V output.

Hope this helps.

 

[Luff]

I built a 12-led maglite head replacement using this converter about a year ago and it works well.

I put two 5mm Nichia leds in series, with six sets in parallel for 12 total. In that layout, the converter pumps about 4.5 volts and, if memory serves, about 35 mA through each LED.

Two negatives to the RS board:

1. Efficiency is NOT good. However, it works and with D cells the efficiency isn't such a huge issue. Still, the converter eats a signficant amount of power. Can't recommend it for much of anything running off of AA or AAA batts.

2. The RS board is pretty big at 1 x 1.5 x .75 inches. I'm not familiar with any AA flashlights that will hold it.

The National Semiconductor's LM2621 demo board is much smaller, you can be make it smaller still, and isn't too hard to adapt to provide the power you need. A search on CPF for it will find you lots of information. This is a good board for someone with limited PCB assembly skills and a good choice to drive a LS in larger flashlights (it can also drive 5mm leds).

The Zetex 300 or ZLT+ board so well researched here by some very knowledgeable folks also has great potential. Even more data is available on it by search.

Mark

 

[aksim]

I have read post after post on most of the mod subjects. My head is swimming with the technical aspects of circuits, converters etc... I was hoping the R.S. converter would be of use, simply because would only require hook up. Is there a converter out there that would only require hookup?

 

[Luff]

jadun:

Yep, I can relate to the overall confusion ... CPF at times reads like a conjubilation of electrical engineers, but these people are passing on some great information! It does take some time to 'get up to speed' ... in my case, I expect to get there in another couple of years, but I'm sure learning a lot and having fun doing mods on the way.

The closest I've found to a 'drop-in' is the LM2621, but others here may have better suggestions. You can remove & replace one resisitor on the board (not hard to do) to match the Vout you're after. Cut off the long female banana plugs that come installed for testing. Solder your battery & LED leads on where they belong and you are done. You can learn how to figure the resistance value to use from the LM2621 datasheet or by reading the long thread below. Or, you can use a variable output option with a potentiometer as Quickbeam does.

If you haven't already, you might want to check out some of the mod web sites offered by some members ... some give step-by-step pictoral instructions. I seem to remember one on the LM2621 modifications somewhere.

A couple threads from search:

National Semiconductor LM2621 Evaluation Board

Gives link to National website

Good luck!

Mark

[EDIT - Great LM2621 variable output mod details are on Quickbeam's mod site at TheLITEsite. I prefer to set the output for one value as required by the LED(s) I'm using since I embed the LM2621 in epoxy in my LS mods for durability/waterproofing.]

 

[JollyRoger]

Might I suggest asking Elektrolumens right here on the CPF? He can most probably make you a simple DC-DC regulated circuit that would simply require hookup.

 

[aksim]

Being in the custom furniture business I know how much one of items can cost. I would expect him to charge a price that would compensate him fairly. I am in the mode of how inexpensively can a mod be completed. I am trying to keep to AAA and AA cells. I have some 2AA lights out fitted with one led running on 1AAA and 2N cells right now but I do not know what kind of run time they will have.(earlier post) My wife has been most generous so far in my quote " obsession with flahlights".