What to do...what to do...

I'm having a problem...I was going to buy one of dat2zips boards for my superlight but I was imformed that the pot on them ajusts voltage not current. I need to make a step up that will run 4 white LEDs. If it was somehow fully regulated that would be even better. Point of this superlight is battery life not brightness, so...

I'd like to put a dimmer on somehow too. I know the batteries might not last any longer on dimmest vs. brightest level (Since the POT is eating the extra power right??) but the dimmer is more for neato factor than it is for battery save factor...

Help me pleeeeeeease...

Saaby,

Using the MADMAX regulates voltage. If you adjust the trim pot on the regulator you can drive the 4 LEDs with this board.

I would suggest you hook the board up, and connect a resistive load to the board and with a voltmeter adjust the output of the MADMAX to around 3.4V. Then disconnecting the battery connect the 4 LEDs wired in parallel. Hook the batteries back up and check the brightness. It should be not as bright as you probably would like.

You can then slowely adjust the trim pot to turn up/down the brightness of the LEDs.

As for adding a dimmer to the circuit requires more work.

There are other ICs that might be a better solution for you than the MADMAX board.

If you need more info on the MADMAX or questions, I'd be more than happy to try to answer them.

-WayneY

Ok well...I'm not afraid to go public if you're not

Can I use the Madmax in the manner you describe and then hook up another pot, as in a dimmer, or would I then just have 2 pots doing the exact same thing? I need something that adjusts current not voltage right? Is what I want to do...

• Possible?
• Possible with a Madmax?
  
  If it's possible lets do it!
  
  I think I've lost my mind, somone want to use one of their nice bright lights to help me find it
  

The trim pot adjusts the amount of step-up. It doesn't burn up extra power.

Here's how the dimmer works:

http://edusite10.tripod.com/led3/max757/max757.html

R3 on the schematic can be deleted. I don't use them and it works fine.

You could build one of these yourself. It's not hard.

Ok...but one question:

How/where does one get the chip?? "Request Samples" from the company or is there a better way??

What stuff do I need for the turn around the ferite core...how do I wind it? By hand or is there a much more scientific way?

Saaby,

Applying a constant voltage is similar to having constant current. You can use a voltage regulator to drive LEDs. If the voltage on the LED is constant, so is the current.

If you really want to tinker, it is best to get a design that uses all or mostly through hole components. The board and components are larger and easier to deal with. My MADMAX board uses all SMT components and is more difficult that the larger through hole components.

Without having the dimmer function any converter should do the trick. Adding the dimming function is not very typical. Most of the small DC/DC step up converters have been focused lately on driving the Luxeon LEDs and driving them as hard as possible. Not that 4 5mm White LEDs are not cool too, the Luxeons have kinda taken center stage.

I would think the MADMAX as is would be a good first step to play with and get something going. If you decide this won't work for you I'll exchange it or work with you on a better solution.

Even if you don't like MADMAX for driving the 4 LEDs you could use it in a minimag style 2AA mod and make a cool Luxeon LED flashlight.

Saaby,

I used a Mad Max to drive 3 LED's and it works great. If you have a digital multi meter that will read up to 200 mA, you can put that between the Mad Max and the LED's and dial in the total current you want ( I would guess somewhere between 100 and 120 mA unless you want to over drive the LED's.

Since the Mad Max regulates voltage, once you have it set for the current you want, I believe you could put in a 1/4 watt pot between the Mad Max and the parallel circuit. This should serve as a dimmer for you. As to the effects on overall current draw from the battery; you would need to ask somebody who knows more than I.

- Don

I've not got a digital multimeter but I do have an old analog one that works well, anyway I have been thinking (For reasons other than just lights too) I need a digital multimeter, what would you recommend for somone on a budget like I am? Let see...I'd spend as much as $50 unless there was really something quite a lot better for just a bit more.

I don't quite think that I am up to building my own circuts...yet (although the information is much appreciated Jeff) so a little later when I have access to a credit card (a.k.a. my dad ) I think I'll get a Madmax board and go from there. Now, another serious question...where do you buy wire? I found all kinds of fancy telephone and audio and network wire and cable on the radioshack website but I couldn't find boring old wire on a spool, is this just something you need to go in store for??

Saaby. Check out this thread. Wavetec DVOM Good luck.

I was looking at the Radioshack website and just for kicks I was looking at their multimeters and I found this...



which is what the meter I have now looks almost exactly like. The one I've got is probably 20 years old and it's a little nicer but it's basically the same meter, casing and all! I just thought that was funny, that's all...maybe it's too early

I got a digtal meter from www.Hosfelt.com for somewhere around $25. It even measures capacitance. Ask them for a catalog. Get one that uses a 9v battery. Watch out for the ones that need 6 expensive button cells.

I use phone wire or speaker wire. Electronic hook up wire is harder to find for some reason.