USB "power injector" for USB host mode

[thoughtfix]

I went and did it again!

http://thoughtfix.blogspot.com/2006/01/usb-power-injector-for-usb-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.

[Mike Cane]

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<

[thoughtfix]

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

[Mike Cane]

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!

[NokNok770]

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.

[Mike Cane]

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")!

[thoughtfix]

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.

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.

[Simon]

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

[augur]

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

[bhima]

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.

[thoughtfix]

This is the power injector completed, with pics.
http://thoughtfix.blogspot.com/2006/01/soldering-iron-repaired.html

[Mike Cane]

Live via 770:

And so bloody jealous!

OK, this is how desperate I am: Would the Nokia flasher work under Puppy Linux?

http://www.pupweb.org/puppy/index.html

I know someone with a Powerbook -- but still running OS 9!

[daveb70]

I realize this doesn't put power where it needs to be, but thought I'd throw this out there anyway for those looking to avoid the AC unit when using a USB hub or those inclined to hack this as well:

http://www.cyberpowersystems.com/CPH420MP.asp

I'm guessing there are other makes/models, but this particular one can be found here and likely a few other places as well:

http://www.compuplus.com/i-Cyberpower-CPH420MP-USB-20-Battery-Powered-4-port-Mini-Hub-1003365963~refer-froogle.html

[thoughtfix]

Excellent find, daveb70. That combined with the no-solder method (using that split USB cable for hard drive enclosures) could make it a one-device solution. It's need a male-to-male cable.

[Mike Cane]

Live via 770:


Tch. Someone has not been reading. That hub was mentioned weeks ago. I also just put it in my "blog" for reference.

BTW, searching for "battery powered USB hub" returns itT near the top of Google results!

[dreaming]

Mike, Since no one else probably want's to stoop to pick up the brown stuff, I just tried flasher on puppy and it works.

[Mike Cane]

Live via 770:

Thanks for that good news. You get the last post from me today.


Zzzz time.

[daveb70]

Tch. I don't/can't read every single post made in these forums, my apologies. It did seem odd that in a thread regarding power/USB the product was not noted. I'm sorry I did not think to search first.

Funny though, since it was brought up weeks ago and my "re-post" hit tonight, someone only just tonight coincidentally(?) added it to their blog, minutes mind you after my post. But I don't care so much about those details, I only point them out when others are themselves so particular about details.

Looks like at least one other may not have recalled/seen that post from prior to the 770's release so repeating it couldn't have been such a calamity nor sin.

I do appreciate your input and thoughts Mike, so keep the blog going!

BTW, I did a google.com search for your quoted phrase and I hit page 10 w/no iTt results-only when I searched "google" from within the iTt site it did hit, of course all hits being iTt based, and even then only after digging in to one of the posts listed. Your google is better than mine :(

Yup, a new tips/FAQ/guide of sorts is certainly in order to collectively maintain all that is discovered.

[michaelalanjones]

I have one of those little cheapie USB Hubs, with an adapter. Will that not work, or does it not do enough?

[fpp]

Read up on the various threads on USB keyboards (unfortunately there are several), all the answers are there. In short : most of these supply power to the devices downstream but not upstream to the host. So you either need to modify them, or use thoughtfix's Y-cable "solderless" hack.