So I wanted a portable way to charge my MP3 player so I wasnt SOL if the internal lithium battery died... Also, I just felt like messing around with making something, so off I went browsing maxim's website, and then digi-key to get the parts on the way. After I designed the PCB I cut a blank. Then I used some scotch brite to polish it up. I used the toner transfer process to mask off the board for etching the masked off board, with some extra sharpie on it to make sure I didnt get any eat-though. I sharpied the whole back to keep the etchant from having to eat the whole unused back side. my etchant reactor The warm etchant works a bit quicker then if it were cold. and the crock pot provides a nice glazed ceramic container that isnt affected by the etchant. after etching, rinsing, and then a rinse in a baking soda solution to neutralize any etchant on remaining on it. After using acetone and a paper towel to get the sharpie off, and scotch brite to get the toner off, the finished PCB Solder up the boost controller IC (MAX608) solder up the small SMT componets ( current sense resistor, diode, transistor, and a ceramic cap) add the SMT aluminum electrolytic caps (which I went overboard with... only need ~150 uf input and output, I put 660 uf each ) soldered up the USB port, the SMT inductor, and the battery holder, which I also superglued to the back to make sure it wasnt stressing the solder joints too much. There you have it, battery powered battery charger in an afternoon. Ive seen smaller ones online, but I think they were only made for ~100mA. This can output a full 500mA, and if I changed the current sense resistor, it could probably output more without a problem, up to about 1000mA or so. With an upgraded mosfet, from the tiny SOT-23 one currently to a larger one, I could increase the output even more. EDIT: oh and if there are any bridged pin on any of the ICs that isnt a mistake, they all got connected together, so I just soldered them like that.
I wish there were more DIY electronic projects like yours. Did you go overboard on the inductor as well? 4.3 amps maybe?
dunno why I was having a hard time finding inductors but I was, and the price was right. I wanted ~1.5-2A saturation current, but I guess 5A wont hurt if I decide to do something else with the 2nd one that I got in the order Up the current limiting by lowering the resistor and I can do 2A peak though the inductor, which would end up about 1A output. Up the mosfet to something that can handle 5A, and then the inductor is my limiting factor, with about 2.5A out, though a 5A draw on the batteries would kill them pretty quick.
You are right about that. I always order more than I need as well since I am afraid of killing one and having to wait and pay for a replacement. Now I have packages of components that just sit around gathering dust because if I put them in my storage drawers, I will have to dedicate each drawer (label it) for each component and later buy more of them so that single one won't be so lonely. It is a never ending cycle!
yeah, I buy extra of things in case I manage to break one... I was taking one of the diodes out of the tape, peeling back the top, as I let go, my finger accidentally flicked the main part of the tape, and it flung the diode across the room. I'm not even going to bother looking for a SOT-23 diode on the far side of the room in the carpet.
I have done that once, but it was a temperature compensated oscillator with square wave output so I had to go hunting for it since they cost about $9.00 per piece.
why is it you need half an amp? or even a full amp? what gargantuan beast is it you have that is named an MP3 player?
I dont know how much power it needs, and it could use up to 500 mA, since thats the max for a USB port. Most likely it doesnt, but an MP3 player that uses pulse charging could possibly use the 500mA for short periods of time. Dont really need it, just overkill engineering.
ooo I like the idea of using a slow-cooker to make a pcb etching tank we have an old one around somewhere cool project btw!
I followed the design in the datasheet for the max608 http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1252 I made the board design up in circad. I would post up the board, but it doesnt really do anyone any good unless they grab the exact same smt componets I had it wouldnt do much good.
