Don't know if this qualifies as mad science, but hopefully it's in the right place.

I just got one of those 6.3" touchscreens from DH405 and it's sitting on my desk taunting me with all the possibilities. My latest idea is to pair it with a Nano ITX motherboard to make a portable Jukebox. It would attach via wireless network to my main Jukebox which has all our music on it. My wife loves the jukebox I built, so this would be a Christmas present for her so that she could take it with her around the house, or into her office, etc.

So here are some questions regarding power.

Watts = Volts x Amps

LCD is rated at 12V 0.8A = 9.6W

Nano ITX board requires 12V and up to 36W. I'll be going solid state for the hard drive and hope I can reduce this a little. One guy reports 7W under load, although I'm not sure what he's doing with it. I'll need enough for a mini-PCI wireless network adapter, USB keyboard, (for setup), and USB memory stick so she can play music from other sources.

Speakers - I'll get a pair that run on 12V DC at xW from an old computer.

So can I say that my 12V power supply needs to have (9.6 + 36 + x) / 12 Amps, so that I can run everything off the one source?

If I threw in 8 D size batteries for when it's not connected to the mains, how do I figure out if they'll have enough to power the thing, and how long they'll last? Portable stereos run off batteries, so I should be able to do it with this, right? I might be able to get an old portable and gut it for the power supply I suppose.

So what do you guys think?

yes add all the watts up and look for a 12 vollt powersupply for that many watts. If you go to rummage sales and see a vibrating back masager, thay are 12 volt transformers usually with a good 1 amp or more.

W = V * A or A=W/V eather way. Once you get your estimated watts or amps, its best to and an extra 20% to 50% before you pick out your transformer or supply converter, you do not want to run your supply at max to keep heat at bay.


if you run it from the mains, check for "kill a watt" most larger hardware stores carie this. or check public libraries, mine does wich is an ac watt meter. though if your using computer parts, an axt powersupply would be more than enough.

if your going D cells, your probally not going rechargeables, as most D rechargables have the same or less capacity than AA size. D cells do last longer.

How do I figure out what watts/amps the motherboard is actually drawing when it's running, if I have it hooked up to an AC adapter? Is there a way, or should I just go for the max 36W? (I'd rather have an idea of what it's actually drawing when it's under it's designed operation.) There's a big difference between 7W and 36W. I have a digital multimeter that has a 10A current measurement, but I've never used it for measuring current. Don't I have to connect it in series, in which case I'd have to rig something up so that I can have a break across which I can connect the meter?

That would be totally awesome, been meaning to build one for my mother in law, please please please, plog this man

Yes.
Best to measure it when you have any and all peripherals (hard drive, minipci card , etc) up and running. Wifi cards can use a surprising amount of power when they are running. Since I dont expect you will need a great amount of processing power, it might be best to look at ultra low power CPUs and then underclock it in BIOS.

Have you used solid state (CF or SD) as a HD before ? Ive converted one of my laptops (a 10" tablet PC) to a CF hard drive, and its great. I would highly recommend a linux setup (and run a RAMdrive), or if you want to shell out the $ (& you dont want to bother with the idea of your wife running linux - though trust me you can make the interface very simple for her if you want to), XP embedded. Flash drives have a limited number of read-write cycles and stock OSes like to write a lot of temp files.

I would advise checking the power draw of the wireless card before you get it too, I made the mistake of not doing that when setting up my ultraportable tablet, and discovered that there is a large variety in draw across models.
If you can fit heatspreaders for the RAM, or think of other nice passive cooling elements for your setup, you might be able to reduce the use of a fan or avoid it entirely... at least ive heard of people being able to do so.

Sounds like a really fun project. Please keep us up to date, would love to read a PLOG

OK. Thanks for the advice.

I'm thinking of an 8GB CF card. I'm not intending it to have any music stored locally, so it just needs enough for the OS and a couple of programs. I'm having to go for Windows XP, because I can program for that, (it's my own software), although personally I use Linux and would prefer to put that on the box. I might investigate programming for Linux instead, since I have until Christmas. So it's not advisable just to put XP on it, but instead go for XP embedded? That's a bummer.

The one wifi card I've looked at was rated at 400mW, and another didn't specify. What kind of draw would you say is reasonable?

The Nano ITX board I'm looking at has an AMD Geode LX800 processor. I haven't compared it to anything else yet, but I'm hoping that it's low enough power consumption/heat output that I can run without fans. If not I'll be looking for something super quiet.

Thanks again for the interest and advice.

@ TheTrustedOne, yeah, I guess I'll have to Plog this. It's going to be cool stuff, (I hope).

For power availability, a laptop battery would likely be a good thing to work from. These have plenty of power available to them, and can often be picked up cheap from laptops that people don't want anymore. These vary in voltage from 9.6 to 14.4V, but I'm reasonably sure that you can find one close enough to 12V.

All batteries should have a power estimate on them, usually in mAh (milliamp hours) If you're drawing 1A, then divide this by 1000 to determine how many hours runtime you'll get. For 12V at maximum runtime, I'd probably use good old AA rechargeables. A bank of 10 in series will give you your 12V. If it's not too heavy, another 10 in parallel with that will double your runtime. (Typical AA rechargeable is 1200mAh which will take a 1A draw for about 1 hour and 12 minutes. A 3A draw -36W- for about 24 minutes.)

As far as speakers go, PC speakers will run on varying voltages. I have a set that actually plug into a USB port and run on 5V. This is pretty typical voltage, actually. It shouldn't be hard to get a lower voltage from your battery/adapter set anyway.

I don't know what your overall enclosure is going to look like, but if you want a small power supply for the mini-itx motherboard, check out the picoPSUs from Mini-Box.com. They don't need any cooling and work very well. You may need the nanoITX adapter for $5. I bought the 12V brick that they offer, but you may be able to drive it with batteries?

FYI, just because a power supply is rated at 300W, doesn't mean that it uses 300W. Power supplies only draw the power they need. So a 60W power supply would not drain your batteries any faster than a 30W power supply, assuming they have the same efficiency.

I was thinking laptop battery, but figured I'd have to come up with a charging circuit then, assuming that it's not separate from the laptop motherboard. Any suggestions on how to overcome that?

Thanks for the advice on the AA batteries though, I didn't know how to figure out runtime. But if one battery @ 3A lasts 24 minutes, 10 are going to give the same 24 minutes, but at 12V right? And 10 + 10 in parallel would give 48 minutes? What about a recharging circuit for these so they don't have to be removed and placed in a charger?

Whatever battery I go with it would be nice to have a power jack that I can plug an AC adapter into to power the unit and charge the batteries. I'll be setting it up this way to start with anyway even if I don't use batteries, but they would be a nice addition. I don't want to go overboard with the extra electronics, so I might just have a switch to change between DC input and batteries. A battery level indicator would be nice though. So much stuff to think of!

The speakers I was looking at using plug into an LCD monitor, so I just guessed they're 12V, but I haven't checked yet. They could just as easily be a lower voltage. I've thought about the USB ones as well.

No, if you have batteries in series, you use the total current. So if you have 10AA batteries in series, and the draw is 3A, you figure the same 3A draw from all 10 batteries. The difference is that you get 3A at 12V instead of at 1.2V.

If the batteries are in parallel, then the draw is split across the batteries. So 10 batteries providing 12V at 3A will go for 24 minutes, 20 batteries providing 3A at 12V will fo for 48 minutes. If you rig the batteries to give 6V, then 10 batteries providing 3A at 6V will go for 48 minutes. (Because there would be 2 banks of 5 in parallel to get the 6V.)

I don't know what the enclosure is going to look like either. The Nano-ITX board I'm looking at though just has a regular power jack on it, so I haven't looked at power supplies as such. I'll check out that link though.

OK, I've just done a bad, bad thing. I've ordered the motherboard, memory, CF card and wireless card.

This site is going to be the death of me!

Here's another question. I have a set of computer speakers I want to strip and use. They plug straight into the mains, but I figured they must have a transformer in them so I took them apart. Sure enough a transformer feeding 10V AC to the circuit board, and then four diodes, (I think), turning that into 12V DC. At least that's what I figure with my limited knowledge and cheap multimeter.

Could I tap off this 12V supply to run the motherboard and LCD screen, or should I get a power supply with enough amps to drive board, screen and speakers? The speakers have 4ohm 3W printed on them, so would that be 6W total requirement, 0.5A @ 12V? Right now I'm thinking I'll need at least a 5A supply.

I also have a bigger set I'm just about to open up.

OK, the bigger set were 10W speakers and the transformer had an output of 14.4V @ 1.0A. I think these are too much for what I need. I want to keep it small and simple and the little speakers sound quite good to me.

Got the motherboard today, and it's teeny tiny. I'll post pictures when I get to work as I have no camera here. I couldn't find an AC to DC adapter locally so I'm going to try powering up with the 12V 1A one I have, with a separate one for the display. This might be pushing it though.

Here's another question for you guys. If I want 12V 6A, how can I get this easily from a 19V 3.79A supply? I have an old laptop adapter I could use, but I need to get the voltage down to 12V. What are my alternatives, aside from looking online for a 12V 6A one? What does it take to build a regulated power supply from a transformer and associated electronics?

One way to convert your power is with a voltage regulator. I am not sure if you can get 6A from a 3.79A source??? I know that you can get 12V from a 19V power supply. Take a look at voltage regulators at Digikey. You will probably need a regulator and a few capacitors since your source is already DC. This one is only $0.90. It is only rated for 3A output, but that is what I limited the search to since your source is only 3.79A.

With a simple regulator you cannot get more amperage than the supply can deliver, no matter the voltage drop. It's not a conversion of watts to watts, it's simply shutting down the voltage.

In order to convert watts to watts, you need a SMPS, and it's easier and more efficient to just convert your 115VAC to 12VDC with one of those.

So even though both supplies are 72W, I can't do it. OK, so I could build my own supply from a 115V AC transformer, the output which will also be AC, make a circuit to convert to DC, easy enough I think. But my transformer output will have to be rated at 6A won't it? The ones I can source locally don't go up that high.

I think it's time to go online shopping again.

(What's SMPS?)

Oh, and currently, (pun intended), I'm running the board off a 1.5A supply, and it's working, but I haven't put it under any serious load yet. Well apart from loading the OS I guess, (which took forever).

Some pics. with beer bottle for scale

Front showing 8GB CF card used as a hard drive.


Back showing 1GB memory and 802.11g wireless card.


Hooked up to 6.3" touchscreen.

Dude where did you get that? and how much is it?

The board was $150 from Newegg. Last time I looked they were out of stock though. OK, I just checked and they're in stock again. Do a search on nano-itx to see if you can come up with alternatives. Also if you don't need anything quite as small you can go for a mini-itx board which is a little bigger and will have more processor options.

I order from Newegg because they have a pretty comprehensive inventory and reasonable shipping to Alaska. They're not the cheapest though, so you might like to shop around if you're in the lower 48. With the CF card, memory, wireless card and shipping it all came to just under $290. :yikes:

I'm having a little difficulty in getting XP to run stable on it, but I want to get a better power supply before I put Linux on it instead. With Linux I'll have to try and get the touchscreen drivers working, (I've tried in the past without success), and I'll have to rewrite my software, something I really don't have time for.

It's going to be a sweet little project though.

So I did a Google search on "12v 6a dc adapter" and the fourth item in the list was a link to this thread!!

But I did find a supplier and it should be here next week. It's only money right?

I would get my self a nice 100w 110:12v transformer and rectify the output. Failing that, you could buy one of those replacement Laptop jobs. They are more like 18V though. Some how, I think the power supply Is going to be bigger than the rest of the guts. If you just want to throw some money at it and make it go away. Then...... http://www.logicsupply.com/products/m3_atx That bad boy will accept any voltage from 6v to 24v. You could run a small SLA. This thing is total excess. I'm thinking you should have gone with a gumstix computer and a graphic LCD.

I found a 12V 6A power supply on line that's $33 shipped. Should be good enough for what I need, if a little spendy. I haven't tried eBay yet though.

I realise it's a bit late but...

SMPS: Switch Mode Power Supply. This basically takes DC, switches it on and off very fast to make high frequency AC, and transforms that. The high frequency can be translated to other voltages at high currents using smaller transformers. Very high efficiency. The new voltage is typically rectified to DC again. This is the way that (for example) a PC power supply works to be able to get all that power into 12 and 5V without a transformer that weighs 60 lbs.

Never too late to learn something new.

In the scenario you describe, what would be the DC source? The 19V 72W laptop power supply? Then you change that to AC, (how much, 19V?), transform it, (to what, 12V?), rectify it to DC, (12V from the transformer?), and end up with 12V 6A/72W, (less operating/efficiency losses?). These may be dumb questions, but I only know the basics when it comes to this electricity stuff.

Anyway, I got my 12V 6A suply today, and will be checking it out tonight at work, just as soon as the day shift goes home.

How about a smaller computer, uses less energy, that you can plug your LCD directly into the mother board! (meaning no video controller board!)





http://www.logicsupply.com/products/px10000g

Nice looking board, and may have been better, but not enough for the difference in price. I'll stick with the nano board and see how it goes before going even smaller.

OK, so I always thought getting XP to run on this might be a long shot, and it was. It installed OK and would run, but kept blue screening at some point. Everything worked though, (wifi, sound, touch screen, etc.)

I've not been having much luck in getting Linux installed though. When I get home from work I'm going to give Debian a try, (I've already gone through 6 other distros with no success). I'm going to try a different approach though, which is going to work! I know it's going to work otherwise this will have been an expensive mistake, and I never ( ) make those kinds of mistakes.

Of course when it is installed I'll then have to learn C++, Java or Python and rewrite my application from the ground up. But I've got until Christmas. That gives me 9 months if we celebrate it in March.

Look into either "Windows XP Embedded" or "Puppy Linux". They all are MUCH smaller versions of OS's that are meant to run on embedded boards. They normally run between 60-160Mb in size (compared to 600Mb-2Gb!) They only really install what is needed for your system, so this means, if you decide to change your system around, you might have to hook up a CD/DVD ROM drive to add the new drivers or support software.


David

(P.S. - I havent used these OS's yet, so I'm just going by what I have read in my research)

XP Embedded would be the way to go for me as I could use my existing program with little modification, but there seems to be no way to get a hold of a copy without spending $1K for a developers copy. With my 8GB CF card install size isn't the issue, I just need something that's not going to run 101 services that I don't need. I've looked at many Linux distros, but not Puppy although I hear it's good. The problem I'm having with Linux is that whatever version I try to install, the installation crashes halfway through. I think it might be a problem with the CF card, I'm going to check that out tonight. I have successfully installed Damn Small Linux to run purely from memory though, so I'm sure I can overcome the problem of installation to the CF card. Eventually.

Remember, I never make expensive mistakes.

Try TinyXP

Never heard of it. Looking it up now. Thanks!

Thanks jonjandran! I looked up TinyXP and following a couple of links I ended up finding nLite, which enables you to make your own custom install of XP with whatever drivers and extra software you might need. I stripped out a lot of stuff and I'm installing it right now. I'll let you know how stable it is when I get home tonight and have a chance to test it out.

Yeah I'll be purchasing the Pico computer (shown above) here shortly to do some of my own testing. I want a very small, portable PC that can fit into a backpack or even pocket, so I can use it as an internet only machine. I want to build it into the back of a 7" or 8" LCD so I can reach the internet from anywhere, download anything, or even DL some bittorrents. I have a small pocket PC that works good in a pinch, however the 320x240 "stylus pen" screen sucks if your doing anything more than checking your email. Plus it doesnt do streaming video very well.

At home I have a 42" Plasma monitor/TV, an 20" LCD screen fed by a laptop (often not attached) and my full fledged Media PC, well this way I can take my mobile Internet machine, and hook it to any of these as needed (beats moving a tower around).

Sounds like a plan!! The Nano-ITX board I have is slightly smaller than the 6.3" touchscreen I'm using, so you might not have to go as small as Pico if you're looking at a larger screen. But of course there's nothing stopping you!! Just thought it might broaden up the options a little.

I think this Nano is running cool enough without a heatsink or active cooling, but I'll probably add something to the final build, just to be on the safe side. Maybe a GPU fan thingy? Or maybe just a heatsink and a small case fan, (not 80mm but smaller than that)?

Well I saw somewhere that the pico uses just a tad bit less power (around 14 watts), plus I'm trying also include (if i do the LCD thing) a battery that will hopefully power the unit for atleast 3 hours. I would like to make it around 5 hours, but batts only hold so much power.

I got a reply from SupraGuy about batteries at the begining of this thread that might be useful to you, and yes, if you're going truly portable then every bit of energy saving is important. I haven't ruled out batteries for this project, but it's looking less likely that I'll worry about them for the initial setup. The most likely scenario for this is that my wife will use it out in her office, and then it can simply be plugged into the AC supply.

The closer this thing gets to being stable then I'm going to try and do some current draws on it to see what it actually runs at. I'll let you know when I have some figures.

I'm coming up to another week off, so I hope to be able to get this mounted up in some kind of frame, everything installed and on one power supply. I will need to find a volume control that will go to eleven though.

Oh, and I need to fix my projector screen and make it motorized.

And lots of other stuff.

All for very little money as I've over spent.

Oh well.

Well something like this could work

Polymer Li-Ion Battery, 3.7V 16,000mAh (68135170)
6.8"x5.4"x.25" <- Might be batter with 8" or 10" LCD


They are a bit pricey (onsale from $159.99 to $69.99) but x2 of these will yield 7.4VDC. The power supply for the pico takes between 6VDC-32VDC. So 3 of these might be the ticket. It will be bulky, how-ever it will allow for almost 10 hours of battery time!!!!!

Pretty spendy! But I didn't realise that the Pico's only took 6V, that's not too bad. I certainly wasn't going to go with anything so elaborate, but like I said I'll probably ditch the batteries anyway. I've already spent more than I should have.

Keep us updated on your progress!

Well this is the plan (who knows if I'll actually do it) but...


Polymer Li-Ion Cell: 3.7V 9000 mAh (PL-809797) , 9A drain rate ($35.00/ea)



3 of these stacked on each other will be about 4"x4"x1" and will yield 11.1VDC (which means you can charge it from a cigarette outlet in a car!) @ 9Ah (~100Watt/Hours total). So on the back of a 8.4" LCD, I could mount these and the Pico next to each other and it should fit. As far as power consumption:

Pico = 13watts
LCD = 10Watts
Pico + LCD = 23 watts.

100 watt/hour battery
------------------------- = ~4.3 Hours (maybe more!)
23 watt usage

And as the batts voltage lowers due to drain, the PSU on the board will compensate! The cut off voltage for the L-ion batts will still be higher than 6VDC, so it'll run until the battery protection kicks in (powers off). This will prevent an under-voltage condition on the motherboard (which could be dangerous!)


They dont take 6VDC, the power supply (micro switch mode) does. I think it still uses the standard 3.3,5,12VCD.

Now if I add a 2.5" HDD to the mix, the batt time goes down. I might do CF or Solid-State HDD.

I went CF (8GB ~$35, maybe less with shopping around, and you can get larger of course).

Are you planning audio, (built-in speakers), or just going with the headphone jack?

I messed around with my stripped version of XP some more and I'm installing my latest attempt as we speak. If all goes well I can write a test app and get it installed for some load testing to make sure I've got a stable set up. It's looking pretty good so far.

Awesome! Well when you finally get something stable going (haha, see what I did there....XP...Stable?) It would be nice to write up a little thing saying what you did, and how it worked out for ya. Plus, if you know of any bench-mark tools, I'd like for you to try them out, and post what you used. It'll be interesting to see how the Nano compares to the Pico!

I get my table scraps (aka-paycheck) on friday, so I'll be placing an order for my pico to begin testing.

Well my Nano only has a 500MHz CPU, so you've already got twice that with your Pico. I think this should still be up to the task for what I want though.

Oh, and I think I'll get a second CF card and try and get Linux on it, although I've had very little success so far.

My thoughts.... Something like this (but just DIY!):

SAMSUNG Q1U-ELXP Ultra Mobile PC Intel Processor A100(600MHz) 7" WSVGA 1GB DDR2 400 40GB 4200rpm Intel GMA950 Windows XP Tablet PC Edition - Retail





After reading it's Watt rating, the battery I spec'ed out could run this thing for over 15 hours!!!!

OK, that puts my thing to shame, and we won't even mention the price.

Still, mine is DIY and a lot of fun to build.

Hey think of it this way, think of putting your nano or even my pico on the back of an LCD TV? Sound familiar? Now it's not going to be any quad-core power-house, but for $200-$300 for these boards, they are small enough you might be able to fit them into an LCD TV WITHOUT case mods! Watch TV and surf the web from a 15" screen in your kitchen! (I know they have these, but most places are selling them at a premium just bc they know they can get more for "All-n-One" deals. And most people are DIY enough to do it)

I've seen a 15" LCD w/ a Pico Via board in it, going for over $1200! Seems like in parts you can do it for under $400.

OK, I have a (seemingly) stable XP install. All drivers are running. I would have started on the frame today, but had to fix the dryer instead, so that's the plan for tomorrow. Once I have the basic frame I'll take some more pictures.

Well some problems today. Firstly I haven't been able to find a thick enough piece of aluminium sheet for the enclosure, and secondly my soldering skills SUCK!!! (And they didn't get any better the more I did.) Anyway, I have the power supply powering all three items, which is a good thing, but the speakers now crackle so I'll have to ditch them. I had to cut cables to remove them from their original enclosures, and decided instead of splicing the cables back together that I'd just solder replacements directly to the PCB. It all looks good(ish), but clearly it's not. I'll get some 12V ones from eBay, even though I hate paying $10 shipping on a $3 item.

I also need a 12" VGA cable, and I got a DB15 connector so I could shorten a cable I have, but with my sucky soldering attempts today I'm not looking forward to doing that just yet. Maybe tomorrow I'll have a go.