MintyBoost! - Small battery-powered USB charger

Step 12 Make: Parts

Next, you'll need your parts

Comments

[jlund]

what r the parts caled i would like to know riten now so i can go buy them befor radioshack closes

[09khanyu]

I would like use this to power an arduino with a 3.7V Li-Ion cell. Would I need to make any changes to the components.

[axeman911]

tedwards right man too high teck dont be a f*cking merd man keep it cool like hippies

[TedWard{}]

this is a really great idea but where the f*ck are surposed to get this stuff. plz, i need a SIMPLE parts list and where i'd get them from (preferably in the uk but just a general idea would be helpful). thanks

[thefallenhero]

Try http://uk.rs-online.com/.

[froggyman]

if you are unsure what parts are needed and since you dont know where to get them, I am assuming this is your first electronics kit. So, just buy the kit from the posted site

[derrick.daniels]

if i need to replace the diode, do i have to replace it with the same one or will any 1amp diode work?

[super_genius]

hey I was wondering if I can substitute some parts.... well most parts with others like some more powerful capacitors.. I think I can still use the female usb port and the socket, boost controller, and diode.... but I think thats all I can use of the right (and the obvious battery case). so do you think I can substitute anything? it still would be all the right things.. just a bit more powerful.. thanks alot for the awesome idea though!!.

[1nstru]

powerful as in "more power"? that would mean P as in U * I = Voltage times Amperage. i just read it up and the MintyBoost! is meant to provide a max of 100mA. ladyada has put a lot of thought and testing into the schematic and layout and she came up with 82% efficiency. that shows her efforts were not in vain as 82% are quite a good value.

if you want a higher amperage, you cannot achieve that by switching one or two elements. oscillator boosters are delicate things and layout and part choice have great influence on them.

if you actually mean "more volts" by "powerful", then this circuit is totally not for you.

judging from your question 8no offence!), you do not have much experience with circuit design or adaption. may i recommend this nifty thing: http://dimensionengineering.com/lvboost.htm
it's drop-dead easy to use and provides over 1A of output current at up to 5V output voltage. if you need more than 5V, they have other adjustable regulators as well, although those others are not as easily powered using standard AA batteries.

[inthesand]

yeah, do you have an actual parts list ? I'm kinda new at this and I think I missed some parts you have here. thanks.

[Richard Davey]

I would like a parts list

[kroq-gar78]

can't you make it yourself?????.......

[1nstru]

L1 - Power inductor, a coil on a ferrite bead. rated 22µH. Chose one with a low DC resistance. 0.02 Ohm (=20mOhm) would be great, any larger value will do but decrease efficiency. i don't want to get into the schematic now, so i recommend using an inductor rated for 2.5A dc to be on the safe side.
use a shielded inductor if you have RFI problems and a non-shielded version if you could not care less. Shield will decrease efficiency but increase compability. i recommend getting the shielded version if you do not build the circuit into an RF-shielded, full metal case. plastic case? shielded inductor. case made by digging a hole into a solid block of gold? extra inductor shielding not necessary.

C1 and C4: ceramic capacitor with 0.1µH
they will not deal with more than 5V so get something slightly higher. other specs are unimportant.

C2 and C3: Electrolythic Capacitors with 100µF and 10V rating.
Chose a "low-ESR" variant. normal ESR types will decrease circuit efficency.

D1: 1N5818 Schottky diode. 1N5817 is better, 1N5818 and SB130 are worse. 1A and 10V, as low forward voltage drop as possible (efficiency!)

(part of this list is repeated below, i wanted to make a complete one for folks who do not wanna bother with my explanatory ramblings.)

[1nstru]

not easily, no. the comments in the picture lack the part attributes. a real bill of materials does not list digikey ordering numbers but part specifications, if possible with margins so even less experienced makers can substitute parts.
i'll try and make a real BoM here:

C2 and C4: ceramic capacitor with 0.1µH
they will not deal with more than 5V so get something slightly higher. other specs are unimportant.
--i had to edit something here, because sloppy me misread the layout, hence the "deleted comment" by me --

C2 and C3: Electrolythic Capacitors with 100µF and 10V rating.
Chose a "low-ESR" variant. normal ESR types will decrease circuit efficency.

D1: 1N5818 Schottky diode. You can substitute this one with any fast-switching diode, as long as it has a very low forward voltage drop (and can handle the current, of course). "Schottky Rectifier Barrier" is your keywords here.

Some general info i coulnd't fine in the tutorial (though they may be hiding somewhere):
the circuit boost the input voltage up to 5V. you are trading voltage for amperage.
example1:
Uin = 2.4V (two well-charged NiMH accumulators)
Uout = 5V
Iout = 500mA (the maximum that USB devises are allowed to drain from one usb port as defined per USB-standard. though some devices might even exceed this most devices drain less)
thus Iout = 1225mA or 1.225A

Uin = 1.6V (two near dead NiMH accumulators)
Uout = 5V
Iout = 500mA (the maximum that USB devises are allowed to drain from one usb port as defined per USB-standard. though some devices might even exceed this most devices drain less)
thus Iout = 1838mA or 1.838A - almost 2A

Iin = (Uout * Iout ) / (Uin * 0.85) (0.85 is the power efficency factor i assumed. if the circuit is actually less efficient, then Iin will have to be larger. i doubt the circuit can be much more efficient than 0.85, but if it is, then Iin can be lower)

this means that the batteries will have to provide this amperage. it does not mean that there cannot be any amperages higher than that within the circuit.

in oscillating applications like this, part choice and pcb layout matter a great deal. we are dealing with around 50kHz or more probably (just a wild guess, if ladyada mentions the circuits frequency somewhere here, please correct me) so you want to stick to her pcb layout closely.

if you make your own pcb, or only copy her pcb at home, then you might want to increase the width of the leads to keep R as small as possible. there's quite some amperage involved. it might also help to increase the area of mass area if you are concerned about RF . try to keep the metal area under the coil to a minimum though, it would decrease efficiency.
if you etch your pcbs yourself, then haveing large leads and mass area will save etchant as well - added benefit for you and mommy nature! also, please do not use FeCl3 (ferric chloride) etchants - they are very yuck.
check this tutorial: http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/
this method is way better, but etching PCBs will ALWAYS leave you with poisonous waste (copper in some sollution, and copper itself is already poisonous), so use common sense.

unrelated: why does the "preview comment" function not work anymore? o_O

[1nstru]

(removed by author or community request)

[1nstru]

i just checked the diode 1N5818:

30V (way more than we need)
1A (also quite enough, D1 only has to handle a bit more than Iout which will not exceed 500mA as per specification of the USB)

this type typically has a very low forward voltage Uf (as i already stated, that is important here), i dug out a max of 0.37V for 500mA Iout. Uf varies for different manufactureres but all manufacturer models of this type will be fine.
1N5817 will be even better because of even lower Uf, and SB130 has been used succesfully as an replacement as well although its Uf is higher. 1N5859 should work as well but will decrease power efficency (higher Uf)
if you want to bother with that: check the diode speed. if the circuit frequency is 50kHz, then D1 has to switch 50,000 times per second. one second divided by 50000 = 20µs. let's say the Diode switches in 20ns, that's a thousand times faster. so D1 will only waste 0.1% of the given time by switching. hoever, that's an incredibly small value, anything faster than 50ns will do. and after checking the circuit once more, i think it will even be slower than 50kHz. ANYwhooo.. long story short: you will not find switching time values in datasheets usually. stick to Uf as your chosing criterium. you will be fine (at least as long as the diode can handle 1A and 10V, it would only have to deal with slightly more than 0.5A and 5V, but Uf will be higher at the top end of its specifications, so overengineering in this part is actually not overengineering but "good design")

[jono456]

 The voltage rating of your diode has to be considerably higher than your design output or input voltages. Spikes generated by this switching circuit are what will kill the diode if you try to find one with a low voltage rating. I would not feel comfortable with a rating less than 20volts.

[mdog93]

are these the right sort of capacitors

http://www.maplin.co.uk/Module.aspx?ModuleNo=318

i'm not sure because it say 0.1uF 50V and you didn't mention anything about 50V, will this component work?

thankyou
Mdog

[1nstru]

these will work fine. however, C2 and C4 will not be dealing with more than 5V, so 50V is overdoing it. the 50V cap will probably be larger than the 10V version. you have to check if it still fits your design.

[Red Ball]

Hey, could you possibly send me a parts list. Would be tres helpful as I am a complete noob at this sort of thing :) thankyou