Cell phone charger circuit PICS added

[Lynx_Arc]

I haven't taken any pictures of this yet but I recently purchased a cell phone charger. It consists of a case that holds 3AAA cells (in series),a 3v lamp, and a dc/dc inverter to plug into a cell phone to charge it. I wasn't sure what the circuit was until I looked up the MC34063A chip and found out it was a DC/DC converter after I noticed an inductor of approx 100uh I believe. With 3AAA nimh cells the circuit outputs approx 8v and using the 10A scale on my DMM shorted across the output I got 1.1A, with only 2AAA in it the voltage dropped to 7.4v.

I am still trying to figure out what to do with this thing, I originally bought it to use with 3 5mm LEDs as a flashlight. Perhaps I may use 2 or 4 LEDs and can extend my runtime longer.

Any suggestions or interest in this thing?

EDIT: added pics and changed title to reflect this.

 

[rdshores]

Re: Cell phone charger with boost regulator

If the inductor is stamped 100, it is usually a 10uh inductor. 100 means 10 with no zeros.

 

[Lynx_Arc]

Re: Cell phone charger with boost regulator

The inductor had no writing on it... it is a color coded green resistor type of inductor with brown black brown bars on it.
I will try to take a picture later today of the circuit, this may be a nice find as it looks to be able to handle a boost current of over one amp at 8volts with some *adjustment* it could be a cheaper drop in module than a dorcy AAA circuit. I just need to find out more about the chip and the wiring of it and do some more real time tests of how well it works.

 

[Lynx_Arc]

Re: Cell phone charger with boost regulator

Ok I got some pics of this gadget.
note the pushbutton for the incan bulb that pushes on a contact touching the lead of a diode.

This is what it looks like before dissasembling which requires only loosing one screw.

here is how the circuit board sits in there.

Here is a closer look at the circuit board pulled out of the charger. The board minus bulb and springs measures .5in x 1.25in and .5in thick or .25in removing switch and contact.

This is the reverse side with the IC and switch for on/off of the charger circuit (red and white wires), note the metal contact below the IC this is part of the lights momentary switch assembly. I *think* the diode is a zener used for dropping the voltage down to around 3v from ~4.5 because I measured the voltage at the bulb using 3 nimh batteries and it was about 3v.

I am still trying to figure out what the circuit is doing.
The instructions say it is for a nextel phone which has a 3.6v battery in it. I am guessing it is set to regulate charging around that level and with possibly some current regulation. It may or may not be doing both boost and buck regulation I don't know yet.

 

[mrme]

Re: Cell phone charger with boost regulator

Wow. Tonight I just bought a car charger for an obsolete cell phone at the dollar store (wanted the twisty wire) and it has the same chip in it. I found a datasheet, but the thing is just a little over my head. If I am reading this right, it can both buck and boost.

It sounds like a pretty cool chip, but the inductor is pretty bulky. It was glued to the top of the IC and I broke it trying to get to the part #.

Now my curiosity will drive me back to the dollar store to buy another one intact to play with.

 

[Lynx_Arc]

Re: Cell phone charger with boost regulator

the inductor on this one is that green resistor looking thing in the upper left corner. I am hoping I can figure this out well enough to possibly change a part or two and use it with 2 nimh to drive 3-10 LEDs in parallel at a decent rate. I have a few 2D lights I would like to put LEDs in including 4 cheap headlamps. Perhaps someone that is into these micro circuits and has a selection of smd parts and a good soldering iron would chime in as this could be a cheap dorcy AAA competitor although I am unsure how many of these I can get there were 5 still on the shelf at the store perhaps a whole box in the back I didn't ask.

 

[Lynx_Arc]

Re: Cell phone charger with boost regulator

I have the circuit set up on a breadboard and get about 40ma out across 4leds in parallel and if I short out a resistor it goes up to 56ma. I am going to have to figure out the circuit diagram although the capacitors are unmarked and the circuit board looks like it may be 3 layers. It may work great for a 5mm boost circuit or possibly even a luxeon with an inductor and resistor swap.

 

[rdshores]

Re: Cell phone charger with boost regulator

The MC34063A chip is the one that was used in Lambda's Ill pill Luxeon drop in module for the Mini maglite, shown HERE
It is also the chip used in Lambda's SMD+ drop in Luxeon module, shown HERE
The SMD+ drives the Luxeon at about 500ma, using a 10uf inductor, 47uf capacitor and a 40V 2A Schottky diode.

 

[Lynx_Arc]

Re: Cell phone charger with boost regulator

yea that looks like it to me, I bet this circuit has a few wrong components to do what I am trying to do with it. Hopefully I can figure out the components I have and adjust them to work but SMD soldering may be fun, I may have to mod my ISOtip iron to work with an external power source since its batteries are weak. It looks like from that page you posted a link to this circuit may be perfect for modding stuff as I can get it cheap as long as they don't run out of these cell phone charger gadgets. I will have to pick up a 10uh inductor to try today and may have to pull the two capacitors off the board and replace one with the 47uf one.
I believe it has a diode but am unsure what it is, it is labeled SS14 or 5514 I am not sure it is SMD.

 

[rdshores]

Re: Cell phone charger with boost regulator

The SS14 is a schottky 40v 1A diode. That should work fine.

 

[Lynx_Arc]

Re: Cell phone charger with boost regulator

Good, now it seems all I need is to get a different inductor and I have a good boost circuit for cheap. I may have to mod all my 2 cell lights if I get this thing to put out 500ma. If I can only get 200-350 I may stop short of doing my 2D lights.
If I can get this thing working maybe I better buy up all the rest of these gizmos for projects. Considerably cheaper than gutting a dorcy if all I need to do is change 2 parts.

Thanks for the input, if I can get by the electronic parts place tomorrow I will try to pick up an inductor or two or a torriod and some wire to wind an inductor.