I went and did it again!

http://thoughtfix.blogspot.com/2006/...host-mode.html

Lots of pics, parts list, and explanation here. All parts available at your local Radio Shack for under $10.

This provides power to the USB client device (keyboard, flash drive, whatever) and provides voltage on the +5V rail needed to turn on the tablet's USB chip.

Edit: When I fixed this post, I also fixed the spelling of the word "injector" so old links may break.

Geez, you should have listed prices.

Multimeter?!!?

And since when does RatShack carry penguins?!

Anyway, if you get this down to a set amount of time to create one, you might want to think about *selling* completed ones. GET BACK, you savages. I'm first in line!! >rubbing my hands over the thought of using that Zippy 610 KB<

There are several things that keeps me from selling them are:
a: I suck at soldering. Good joints take me 3-4 attempts each.
b: I couldn't justify charging people for my time on something that's just so darn simple (though time consuming)
c: There's no way I could guarantee that they'd continue to work over a long period of time and won't cook the machines to which they are attached.

Hence the disclaimers all over my blog

Full disclaimer here: http://thoughtfix.com/disclaimer.html

Well, if you live in NYC, you can get a new Cold Heat iron on 5th Ave & 38th St. A discount store sells them for $20 -- minus the wire stripper (grrr!). I guess you broke the tip by dropping it?

And if someone like *you*, who *owns* a soldering iron, can't do soldering so easily, then there is *no* hope for me!

I don't know how you use that cold heat soldering gun. I do know how to solder, but not with this thing. I got 1 at costco for 20 bucks...came with the wire stripper. This thing sucks...don't buy one if you planning. It has a built in light, but when you use the soldering iron, the light flickers making it almost impossible to see. And the tip...you gotta place this thing exactly right or it won't work...the tip is too big. Oh and the wire stripper....sometimes it doesn't do it right...and for small wire it just cuts it.

Who wants to buy mine....I'll sell it for 10 dollars. I hope I find my regular soldering iron...it's packed up in a box somewhere during a move.

Thanks for that warning. OT, but on for TV ad products: I picked up this $10 Titanium electric razor. Double blades have been dull (I think they want to scam us into buying those more useless triple blades!), so I decided to give an electric a shot (my first one!). OK, so it doesn't cut as close as a blade; to be expected. But the kicker was in the insert: A life expectancy of just *six months* ("depending on use")!

The instructions are clear: You can't treat it like a "normal soldering iron." I broke it by pressing down too hard and snapping the tip. Grr.

And yes - you have to hold it JUST RIGHT. It's useless for PCB soldering really ... but makes fast work out of little wire jobs like this. If you do it right. Heh.

One tip about soldering is you need a decent iron. So many people I know say they're bad at soldering then you find out they were using some 30 year old thing that's about 100 watts and has a tip made from rusty steel half an inch thick. It's like most things. Having the proper tool for the job really helps.

I am going to make up a similar little box but mine has 5 AAA NiMH rechargeables in it with a low voltage drop out 5 volt regulator. It has a USB socket on one side and a pigtail on the other to go to the 770. I'll chop up the little cable that came with it for that assuming it has all four wires in it. If there is space in the box I am also putting in a small charging circuit so I can plug any 12 volt or so supply into it to recharge the batteries. Nothing fancy. Just charging at C/10 so I don't need a fancy circuit. Will take 15 hours or so to fully charge but I can leave it connected most of the time to keep it topped up. The batteries are 900mAH and so should easily power a USB keyboard for longer than the 770s battery life.

I'll take some pictures when I make it, probably tonight. I haven't rushed so far since my USB keyboard hasn't arrived yet!

Simon

given that is has been over 10 years since i did anything more than a little soldiering i read the whole of the post including all the hackaday post with interest and have a couple of questions/queries

it seems that using a 5v voltage regulator like the lm7805 is recommended over a 5.1v zener diode + resister because "A resistor and zener diode make an extremely poor voltage regulator" (hackaday comment) since the n770 is what i would call sensitive electronics would it not be prudent to use a voltage regulator instead?

As a voltage regulator needs a few volts over the desired voltage what is the recommended amount - i was thinking about using a 9v/7.2v rectangular pp3 (alkaline/rechargable) as it would be smaller (and cheaper?) over 6 aaa rechargeable (6*1.2=7.2) i suppose i could use 4x1.5v aaa but i dislike non-rechargeable solutions and i am not sure if 6v is enough for a voltage regulator setup.

now if only there was a way to easily connect more than one device at a time - i think plugging a mini usb hub into one side might enable n770 + usb keyboard + usb mass storage device

augur

I'm planning to make a power injector based on a simple DC/DC converter. It'll take a pair of AA batteries - supply your own. It will have a mini USB cable coming out one end, which will plug in to your 770. The unit will have a USB type A female socket.

I'm guessing that it'll end up selling for around $20. It's possible that the price may go up slightly depending on the costs of parts, as well as assembly - I'm trying to find power supply chips that are easy to solder, but most of the efficient switched mode ones are microscopic, and require both careful soldering and a good circuit board.

I'm also thinking about whether to try to hack a power supply into a USB hub. That's a bit more of a challenge since you want the _smallest_ hub you can - but you want batteries in it too. And you want to charge them. The power injector is a bit simpler, since you can just pop out the AA's and put new ones in. Also, USB hubs vary in price a lot. I don't want to buy a couple dozen hubs to find one that is the right size - so if anybody has any hubs that would fit batteries, and would work nicely on the 770, let me know please

Depending on power measurements, I may be able to do this using smaller or fewer batteries - depends on how long you want to run the thing for, etc.