Another way to charge the PE??

[ivanjt]

Originally Posted by arcticmaniac

what's the shipping charge, lol. yeah, its getting alittle more complicated. however, i think the archos 70 uses the same ac charger so i might look into that.

In fact if you start with a 12v charger it is a fairly simple matter to add a LM7805 and a USB socket on a short lead for 5v @ 1A output (assuming the charger outputs more than 1A.

[arcticmaniac]

Originally Posted by ivanjt

In fact if you start with a 12v charger it is a fairly simple matter to add a LM7805 and a USB socket on a short lead for 5v @ 1A output (assuming the charger outputs more than 1A.

thanks, i was looking at the spec sheet for the lm78xx models, nice. they actually have it at radio shack for $1.79. hmmm, i think i might have to do some experimenting.....ah, its been awhile since i've done it, back in the day, gotta get the old soldering iron out

thank you ivanjt

[arcticmaniac]

Originally Posted by ivanjt

In fact if you start with a 12v charger it is a fairly simple matter to add a LM7805 and a USB socket on a short lead for 5v @ 1A output (assuming the charger outputs more than 1A.

cool,
i found this at radioshack
http://www.radioshack.com/product/in...tId=2062600&cp
and the dc plug, which i think this is it
http://www.radioshack.com/product/in...ductId=2102487

I've got a bunch of 5v ac adapters around i can play with

[ivanjt]

You need to start with a 12v power supply to be able to step down to 5v. The only way to get 12v from a 5v supply is to use a DC to DC converter chip as I mentioned before.

I have a couple of units I've made from a basic 12v @ 2A supply which I put in a slightly larger case with a LM7805 and a USB socket to give me a 12v and 5v output.

[arcticmaniac]

Originally Posted by ivanjt

You need to start with a 12v power supply to be able to step down to 5v. The only way to get 12v from a 5v supply is to use a DC to DC converter chip as I mentioned before.

I have a couple of units I've made from a basic 12v @ 2A supply which I put in a slightly larger case with a LM7805 and a USB socket to give me a 12v and 5v output.

According to the spec sheets i found, it says input voltage range is between 5 and 18V. The chip I found was lm7812 with the last 2 numbers LM78xx is the output voltage. So I'm hoping this chip will step up the voltage from 5V USB to 12V output. the specs says peak current is at 2.2A which i believe depends on the load (from what I remember from my EE days). Any ideas on what to put the circuit in so it does not look so "fugly"?

BTW ivanjt, really appreciate your help. yes, its easier to buy another AC 12 v adapter (which I found at Walmart's website for a universal one) but I want a USB one instead. I'm not looking for something that will provide enough load to use/charge at the same time. i'm fine if its just a trickle charge to get it juiced up overnight, especially when travelling.

[emusan]

thats a voltage regulator, which AFAIK will only reduce the input voltage much like ivanjt said, also, as I said in another thread, you wont get enough of even a trickle charge unless its hooked into a wall adapter with ~1A output. You don't /have/ to use a DC-DC converter if you don't want to, but the alternatives are /not/ fun lol.

[ivanjt]

Arcticmaniac, all of the LM78xx chips are voltage regulators, i.e. they regulate the input voltage, that must be HIGHER than the output voltage, to what ever the last two numbers are.

Next thing, when you say you want a USB charger what do you actually mean? If it is something that you plug into a computer USB socket then it will never work because the current available is too small. If, on the other hand, you want something that plugs into mains power then start with a 12v unit and add the 5v regulator and a USB socket.

When I get home tonight (midday here now) I'll take some pictures to show you.

If you added a concentric socket you could make an extremely small (10 mm x 25 mm x 5 mm) unit that you plug the 12v plug into and then plug the USB cable into for charging your USB charged devices.

12v mains charger ----> 5v regulator module ----> USB device.

[arcticmaniac]

Originally Posted by ivanjt

Arcticmaniac, all of the LM78xx chips are voltage regulators, i.e. they regulate the input voltage, that must be HIGHER than the output voltage, to what ever the last two numbers are.

Next thing, when you say you want a USB charger what do you actually mean? If it is something that you plug into a computer USB socket then it will never work because the current available is too small. If, on the other hand, you want something that plugs into mains power then start with a 12v unit and add the 5v regulator and a USB socket.

When I get home tonight (midday here now) I'll take some pictures to show you.

If you added a concentric socket you could make an extremely small (10 mm x 25 mm x 5 mm) unit that you plug the 12v plug into and then plug the USB cable into for charging your USB charged devices.

12v mains charger ----> 5v regulator module ----> USB device.

I just found out the hard way today. I actually got the LM7812 and noticed that any voltage that i place on it gives me back less than the input voltage. Which you are right, the input has to be higher than the output. What I wanted to build was 5V usb ---- > 12V -----> edge.

LM339 work?, not sure if I can use an op-amp to do it.

ivanjt. thanks for you help though. i think i'm gonna scrap the project for now between school and work and kids, gotta balance it out. was hoping for a simple project, but its been over 20 years since EE school. Will try wally world for one of those universal ac adapters for now. Hope those work.

[arcticmaniac]

Originally Posted by emusan

thats a voltage regulator, which AFAIK will only reduce the input voltage much like ivanjt said, also, as I said in another thread, you wont get enough of even a trickle charge unless its hooked into a wall adapter with ~1A output. You don't /have/ to use a DC-DC converter if you don't want to, but the alternatives are /not/ fun lol.

thanks emusan, i found that out today. the alternative is not fun.

[Last_of_the_PEs]

Originally Posted by arcticmaniac

thanks for the vote of confidence last_of_the_PEs. ivanjt just got me all the parts I needed, lol. back in the old atari 800 days, i used to program and build my own set of controllers (granted only a punch of switches, cables, etc. I dont know if radioshack sells it anymore, (I think that's where i got it from), but i've etched circuit boards before. now im just too old for all that.
i want to like the PE but what kills me is all the proprietary chargers (12 volts on top of that) rather than standard usb charging. i was going to get the streak for about 280 but once i saw the docking port, i said forget about it....i did find some universal ones online at walmart and amzn so i might give those a try. they at least go up to 12v.

Yeah, I also hacked around with the Atari 800 -- didn't change the laws of physics.

[Last_of_the_PEs]

Originally Posted by ivanjt

There are some very compact units that take mains power and have both USB and 12v output - at least over here in Europe, problem is I don't think they will run off US 115 v AC.

Well there you go, cheating again. Obviously if you start at 220 volts AC, everything changes. Higher voltage was used in some places to save money on copper since it is the current (halved by doubled voltage) that necessitates conductor gauge. Yeah, it tends to FRY more people, but I guess life isn't worth as much across "the pond"! LOL! With people so packed in, you need to roast a few to keep things thinned out.

The original adapter is the size of a breath mint tin. Is it really that big a deal to carry it?

[syclone]

It seems to me that any voltage adapter you build, by the time you encapsulate it, will be the same size as the original PS. So there seems to be no gain there. Of course if this is a "project", I can fully understand ! I once took 6 months and spent $100.00 in silver solder building a steam boiler for a silly little steam engine. And that was in 1955 when $100.00 was serious money.