Just a note on the Altiods/Sucrets/DIY versions. If you use two 9 volt batteries, run them in parallel to keep voltage ~9. In series, you will be giving your regulator 18v and making it drop 13v to get your 5v out! Most of your battery juice would then end up as heat emanating from the regulator.
I learned that AFTER I made my version 1 in the Sucrets pack. I have read a lot in the last few weeks.
The goal of version 2 was to be smaller, use ONE 9V rechargeable, use an input capacitor and use a tin case with the 7805 using the case as a heatsink. I learned during the creation of USB Battery Extender Version 2 that I should have some polarity protection, but it was too late to incorporate it at that point, it was 2AM! That would have ot wait for Version 3.
So, it was later and I was moving along and being a humble man I will now admit, in public... I F'd it up and had made the space for the battery too small and here it was completed and the 9V batt would not fit. DOH! I had been so careful, but in the end I failed. I put it aside and figured, "eh, lesson learned" and went to get a new 7805 to begin Version 3. I had to grab some more 9V batt leads and noticed a holder for a "N" battery, it is like a 1/2 size AAA. I asked the guy what batter it held and they had several, from 3.5V to 12V. I thought what the hey, it would allow me to salvage the Version 2 that the 9V doesn't fit in.
This is Version 2...
http://fecundswamp.peanutonastring.com/usb_batt_v2/
The battery has a little nook built in so it can be store in the bag for transport
when not in use.
You can see the screw that attaches to the standoff that attaches to the 7805...
this will act as a heatsink... I hope!
The lid does shut, it just isn't in this picture... I thought I was doinked when I realized
the lid did NOT shut after I installed the USB adapter... a quick zip with teh dremel
cutting tool an it shuts perfect.
I used the PS/2 to USB adapter again, I always knew that they would be useful someday. It has a 22uF Polyester Film Cap on the input, it uses a 10mm Standoff to connect the 7805 to the board & the tin, acting as support and as a heatsink. And this has no polarity protection, but it isn't so important now as it uses the Type 23A 12V battery. I will probably use this once and then never again, unless it lasts a really long time... the battery is like $3.80... but it really made me laugh that I could save my failure from utter uselessness. I wish I could get these in rechargeables.
I found this site useful for helping me understand the reverse-polarity issue...
http://www.maxim-ic.com/appnotes.cfm/appnote_number/636I wish I could find a site to explain how to figure out what capacitance to use though. The datasheet for the 7805 shows a 22uF cap on the input, so that is what I used... I have no idea if that is good or bad... I am dangerous, aren't I? Just enough information to F everything up.
thanx,
michael