DIY Triple Screen Desktop Setup

[DezGalbie]

I've started planning out a little project for myself. I want to salvage some display panels from broken laptops (hopefully on the cheap) and use them to create a triple screen desktop setup for my PC.

I've never done this kind of thing before so there are some questions which hopefully someone more knowledgeable can help with!

From what I understand, I would need to source specific controller boards for the specific model(s) of panels being used in the setup. So I need to know which exact model of panel(s) I'm aiming to source. I would like 1080p minimum (the higher the refresh rate the better). Does anyone have any recommendations for a model of panel to use (keeping in mind that the more laptops there are out there with that panel the better, due to the ease of being able to source a broken laptop which uses that panel). Essentially I'm looking for a model of 1080p panel that has been used in a very popular model of laptop, or that has been used in lots of different models of laptops.

Also, if the panels use 12v power, am I correct in saying that I would be able to power them via USB by using one of these to convert the 5v USB power to 12v, as long as the panels do not draw more current than can be safely supplied by the USB port (which I think is 2A, right?)?

Any advice is appreciated

[mariushm]

It's not really worth it.

You have to buy controller boards separately, deal with power supply issues etc

 

You can buy older LCD monitors for very cheap, and simply take out the processor board and the panel and remove the plastic case and the power supply board.

You can buy separate inverter boards from eBay if the panels use fluorescent lights.. and those typically run with 12v..20v power supplies. The led backlit monitors typically have smaller power supplies but depends from monitor to monitor and how the leds are arranged (some use 20-40v for backlight, others use 60-100v) so it's a bit more difficult to say what you'd need for the backlight.

 

IF you were in US, you could buy 1080p monitors for around 50$ each, here's a HP 20.7" 1080p monitor for 60$: https://www.newegg.com/Product/Product.aspx?Item=9SIAHJM7WS3137&ignorebbr=1

50$ gets you a 19.5" 1600x900 monitor : https://www.newegg.com/Product/Product.aspx?Item=N82E16824160389&ignorebbr=1

 

You can probably find similar deals in UK or Scotland... I know I can find here 22" 1680x1050 monitors for around 63$ including vat and free shipping so you should also be able to find such deals there.

 

So yeah, even if you'd buy a broken laptop for let's say 20-30$, at the end of the day when you add the cost of the processor board and the power supply (which you can simply extract from a monitor), you probably end up at around the same price.

 

 

[DezGalbie]

6 minutes ago, mariushm said:

It's not really worth it.

 

Yeah, I get what you mean about the cost involved. You can get cheap controller boards online from China that come with a power supply etc but even then there's not much saving.

But I would like to do it anyway for the learning experience and the satisfaction of having built it myself. And it's nice to be able to recycle some parts which would otherwise just end up in an e-waste pile somewhere (at best) or landfill (at worst).

Plus I want to power the setup via USB to prevent me having to plug in 3 standard power cables to the wall. It will look a lot cleaner.

[Pixel5]

7 hours ago, DezGalbie said:

Yeah, I get what you mean about the cost involved. You can get cheap controller boards online from China that come with a power supply etc but even then there's not much saving.

But I would like to do it anyway for the learning experience and the satisfaction of having built it myself. And it's nice to be able to recycle some parts which would otherwise just end up in an e-waste pile somewhere (at best) or landfill (at worst).

Plus I want to power the setup via USB to prevent me having to plug in 3 standard power cables to the wall. It will look a lot cleaner.

powering this via USB will not work at, the power you can draw from USB is far too low for any kind of bigger display.

 

also the building experience here is pretty simple and not really a big learning experience as its just connect cables where they fit and you are done.

[DezGalbie]

31 minutes ago, Pixel5 said:

powering this via USB will not work at, the power you can draw from USB is far too low for any kind of bigger display.

 

also the building experience here is pretty simple and not really a big learning experience as its just connect cables where they fit and you are done.

Hmm... based on what I've read I really don't think that's right. USB can handle anything up to 3A of current (depending on which generation of USB it is of course.

And, from watching this guy's testing, we can see that a typical panel requires less than 0.8A at 12V.
 

What am I missing here?

The building wouldn't simply be plugging in cables where they fit. It would be stripping panels from laptops, making my own power bricks to convert 5V USB power to the 12V needed by the panels, wiring up the controller boards, and manufacturing some kind of thin box frame with speakers which can either be mounted on the wall or secured to a monitor mount.

Granted, it may not be the most difficult thing in the world, but it most definitely qualifies as useful experience for someone trying to learn electronics and fabrication.

Please tell me where I am going wrong regarding the USB power issue. Thanks.

 

[mariushm]

1 hour ago, DezGalbie said:

Hmm... based on what I've read I really don't think that's right. USB can handle anything up to 3A of current (depending on which generation of USB it is of course.

And, from watching this guy's testing, we can see that a typical panel requires less than 0.8A at 12V.
 

What am I missing here?

The building wouldn't simply be plugging in cables where they fit. It would be stripping panels from laptops, making my own power bricks to convert 5V USB power to the 12V needed by the panels, wiring up the controller boards, and manufacturing some kind of thin box frame with speakers which can either be mounted on the wall or secured to a monitor mount.

Granted, it may not be the most difficult thing in the world, but it most definitely qualifies as useful experience for someone trying to learn electronics and fabrication.

Please tell me where I am going wrong regarding the USB power issue. Thanks.

 

USB 2.0 ports are 5v at 0.5A = 2.5w 

USB 3.0 ports are 5v at 0.9A = 4.5w

Motherboards in general group four ports and use a resettable fuse configured for 2A ... so 10w per group of 4 ports.

 

And, from watching this guy's testing, we can see that a typical panel requires less than 0.8A at 12V.

 

That's 12v x 0.8A = 9.6w

 

A cheap step-up regulator that would take 5v and produce 12v would be only around 85% efficient ... in other words in order to produce 9.6w  only 85% of the total energy was that amount, 9.6w  ... So  100% would be 9.6w x 100/85 = 11.3 watts

 

A usb charger thing may output 2A at 5v ... that's still only 10w

 

What makes more sense for you is to find a laptop adapter that's designed to output 12v or 18.5-20v at a low amperage, like let's say a 12v (40-65w) laptop adapter - you can power the backlights of all displays from 12v and use a step-down regulator (for example a car usb charger thing that takes 12v or 12v..26v and produces 5v for the display boards (if needed)

 

[DezGalbie]

2 minutes ago, mariushm said:

USB 2.0 ports are 5v at 0.5A = 2.5w 

USB 3.0 ports are 5v at 0.9A = 4.5w

Motherboards in general group four ports and use a resettable fuse configured for 2A ... so 10w per group of 4 ports.

 

I don't plan on powering it through a motherboard with a 2A fuse though, and you're skipping over USB 3.1 which can output upto 3A.

If I powered them using USB 3.1 ports with no 2A motherboard fuses in sight then where is the problem?

I could use a powered USB 3.1 hub which would be good for 3A. 3A x 5V = 15W.

85 x (15/100) = 12.75

So a USB 3.1 port could power a panel upto 12.75w if I was using a voltage regulator which was 85% efficient to go from 5V to 12V, right?

12.75W is more than enough. Am I still missing something?
 

[fargonaz]

Also, after getting the power taken care of you would need to figure out how you're going to drive and sync the panels with your desktop GPU.  Things like this make my brain hurt now.

 

Good Luck!

[DezGalbie]

8 hours ago, fargonaz said:

Also, after getting the power taken care of you would need to figure out how you're going to drive and sync the panels with your desktop GPU.  Things like this make my brain hurt now.

 

Good Luck!

I hadn't considered that this would involve more than simply plugging display cables between the GPU and the controller boards of the panels.

 

Is there more to it than that?

[fargonaz]

I've disassembled more than a couple laptops and none of them had a connector that would easily connect to a common  desktop video card.

 

Maybe I'm not understanding exactly what you're trying to do.

[DezGalbie]

32 minutes ago, fargonaz said:

I've disassembled more than a couple laptops and none of them had a connector that would easily connect to a common  desktop video card.

 

Maybe I'm not understanding exactly what you're trying to do.

Oh, I see. Well that's where the controller board comes in. The controller board has the audio and video input ports. You wire that up to the panel and it acts as the go-between for the GPU and the panel.

You have to buy these separately because laptops tend to have their controllers integrated into the rest of the hardware and it's hard to re-use them along with the panel.

[DezGalbie]

On 2/14/2019 at 9:42 PM, Pixel5 said:

powering this via USB will not work at, the power you can draw from USB is far too low for any kind of bigger display

 

 

23 hours ago, mariushm said:

USB 2.0 ports are 5v at 0.5A = 2.5w 

USB 3.0 ports are 5v at 0.9A = 4.5w

Motherboards in general group four ports and use a resettable fuse configured for 2A ... so 10w per group of 4 ports.

 

And, from watching this guy's testing, we can see that a typical panel requires less than 0.8A at 12V.

 

That's 12v x 0.8A = 9.6w

 

A cheap step-up regulator that would take 5v and produce 12v would be only around 85% efficient ... in other words in order to produce 9.6w  only 85% of the total energy was that amount, 9.6w  ... So  100% would be 9.6w x 100/85 = 11.3 watts

 

A usb charger thing may output 2A at 5v ... that's still only 10w

 

What makes more sense for you is to find a laptop adapter that's designed to output 12v or 18.5-20v at a low amperage, like let's say a 12v (40-65w) laptop adapter - you can power the backlights of all displays from 12v and use a step-down regulator (for example a car usb charger thing that takes 12v or 12v..26v and produces 5v for the display boards (if needed)

 

This kind of hub is exactly what I'm looking for. I can attach it to my desk and have the screens plugged into it with USB cables.

The first port is a smart port which can output at 12V 1.35A without any need to step the voltage up and lose power through a regulator. So that would be delivering upto 16.2W, right?

The rest of the ports output 5V 3A. So if I use a cheap regulator @ 85% efficiency to step up to 12V then those can output up to 12.75W each (upto a total for the entire hub of 12A).

So each individual port is more than capable of powering a panel, and the hub overall is more than capable of powering 3 panels. I could even have an extra port for charging my phone.

Could anyone confirm that this does actually make sense and that I'm not making a fool of myself before I go buying parts! Lol. I've only had people telling me it can't be done but I don't see why not.

[mariushm]

What's with the usb fascination, honestly...

 

If you're gonna put there a device like that, why not just go with a 12v power supply from the start ?

 

See here examples:

wallwart style, laptop adapter style : https://www.digikey.com/short/p321zn

industrial power supply style : https://www.digikey.com/short/p321h8

 

Just cut the DC jack and put 3 separate connectors on those + and - wires, or as many connectors as you want.

Or in the case of industrial power supplies, just connect the wires to the terminals...

 

Makes no sense to buy a usb hub , then have 5v->12v converters, when you can spend 10-15$ on a 12v power supply and simply make a cable or tiny adapter board to convert the single barrel jack into multiple barrel jacks.

For example, you can buy pre-made cables with barrel jack at the end, here's example of the most common ones 2.0mm/2.1mm/2.5 mm inner diameter  and  5.5 mm OD length : https://www.digikey.com/short/p32154

Here's the connectors you could put on a tiny adapter board: https://www.digikey.com/short/p321r3

 

So for example you buy a power supply that outputs 12v 40-60w and it has a 2.1mm ID / 5.5 mm OD connector on the cable.

You can buy a connector with 2.1mm ID / 5.5mm OD (see link above) and solder it to a tiny circuit board (or screw to a panel / box case / wall, there's all types of connectors)  and then solder to the same tiny circuit board the three cables with barrel jacks for the three controllers - now you have a power splitter, splitting the 12v from the power supply to three separate cables, nicely going to each monitor.

 

 

 

 

 

 

[DezGalbie]

2 minutes ago, mariushm said:

What's with the usb fascination, honestly... 

1

It's not a fascination. USB is just how I originally planned to do it. I know that there are other ways to do it. But at this point I'm trying to make sure I understand the theory of how it works. I'm being told that it can't be done, so if that's right - that it can't be done - then my basic understanding of electronics is seriously flawed and I don't want to go trying to make anything until I fix my understanding.

So could you tell me why it won't work? Because I really don't understand at the moment. All the numbers seem to work out in my mind.

[mariushm]

It would work, but in general those usb hubs are not designed to work 24/7 outputting a lot of power.

They're basically designed with the idea that at most, a person's gonna plug 2 phones and charge them for less than an hour, they're not designed to output for hours a lot of energy.

The hub in your link can certainly output 60w through all its usb ports, but I think you'll find that after around 10-20 minutes, it would be uncomfortably warm, like 50-60 degrees. Even at around 30 watts (the equivalent of 3 controllers / panels / whatever) it would be hot.

If outside the hub it's hot, you can image how hot it is inside, because these devices are fully sealed for safety reasons (so water,dust, crap in your pockets doesn't get inside the hub) - basically if you're powering the panels for hours every day, you can expect the hub to eventually degrade, maybe in 1 year or so it would simply fail, due to cooking itself inside.

 

Besides this problem, you also have to consider losses in the usb cables. Unless you have cables with good thick wires inside, at 3A of current there's gonna be some losses.

You'll want to put the dc-dc converters that boost 5v to 12v right near the usb hub, otherwise you have losses.

 

For example, let's say you have a 1 meter length of usb cable and the cable uses AWG24 wires - AWG24 wires have a resistance of 85 mOhm per meter.  So, since the current has to go to device and back, you have 2 meters of wire between your usb hub and the controller board. 

You can now use Ohm's law formula Voltage equals Current x Resistance ... so V = 3A x 0.085 ohm x 2 meters  = 0.51 volts ... so if the usb hub outputs 5v and the dc-dc converter is one meter away, that converter's only gonna see 4.5v at 3A...

 

Higher voltages means less current, which means less loss in the wires, higher efficiency etc..

 

In comparison, those wallwarts or laptop adapter style adapters are designed from the start to be fully passively cooled, will stay relatively cool, and will output all the power on a single connector, so you don't have to stress about reaching the limit of individual connectors.

 

[DezGalbie]

2 minutes ago, mariushm said:

It would work, but in general those usb hubs are not designed to work 24/7 outputting a lot of power.

They're basically designed with the idea that at most, a person's gonna plug 2 phones and charge them for less than an hour

 

2

Yeah, I really don't plan on having the screens on 24/7. Maybe like 4 hours a day at most.

If they were designed to handle 2 phones for an hours charging then I don't see why they would engineer it to handle 12A and stick 6 ports on the thing. There aren't any 6A phones, are there? A rapid phone charger typically uses something like 2A. So 2 phones fast charging in this thing leaves 4 empty ports and 8A of current underutilised.

I get that pushing something to its absolute limit in terms of rating can reduce its lifespan and cause a buildup of heat, but you can go over one third of the rated current without it being a problem, surely? Even with my plan with these 3 panels it would be drawing less than 50% of the rated 12A. That seems fine for long term use at about 4 hours a day.

But regardless, now that we know that it does works I can move on to thinking about the best way to do it. It may be USB hub for the flexibility, or it may be some other way like you suggested. Cheers.

[MrJoosh]

On 2/16/2019 at 12:57 AM, DezGalbie said:

Yeah, I really don't plan on having the screens on 24/7. Maybe like 4 hours a day at most.

If they were designed to handle 2 phones for an hours charging then I don't see why they would engineer it to handle 12A and stick 6 ports on the thing. There aren't any 6A phones, are there? A rapid phone charger typically uses something like 2A. So 2 phones fast charging in this thing leaves 4 empty ports and 8A of current underutilised.

I get that pushing something to its absolute limit in terms of rating can reduce its lifespan and cause a buildup of heat, but you can go over one third of the rated current without it being a problem, surely? Even with my plan with these 3 panels it would be drawing less than 50% of the rated 12A. That seems fine for long term use at about 4 hours a day.

But regardless, now that we know that it does works I can move on to thinking about the best way to do it. It may be USB hub for the flexibility, or it may be some other way like you suggested. Cheers.

I think that the basic takeaway for you here is that it will work, but there are much better and easier solutions to your problem out there.

 

If you want to do the USB technique, go for it. If you want to do it in a way that is more efficient and makes more sense, see the posts above.

[DezGalbie]

3 hours ago, MrJoosh said:

I think that the basic takeaway for you here is that it will work, but there are much better and easier solutions to your problem out there.

 

If you want to do the USB technique, go for it. If you want to do it in a way that is more efficient and makes more sense, see the posts above.

I can understand that point of view completely.

What I couldn't understand was being told that it was physically impossible because a USB port could not provide enough power. That was the sticking point. I had the facts telling me that it definitely was possible.

But now that we're all on the same page about it being possible I can, like I say, decide whether to do it via USB or via another method like suggested.

[MrJoosh]

15 hours ago, DezGalbie said:

I can understand that point of view completely.

What I couldn't understand was being told that it was physically impossible because a USB port could not provide enough power. That was the sticking point. I had the facts telling me that it definitely was possible.

But now that we're all on the same page about it being possible I can, like I say, decide whether to do it via USB or via another method like suggested.

I think that the issue was that people were assuming that by "USB port" you meant a USB port on a motherboard, and not on a USB power device like a charger etc. There are some realistic concerns about power draw and efficiency whilst using a USB cable to transmit the power though.

 

With my OnePlus6, testing USBA -> USBC cable that came with the phone compared to a generic cheap one, the internal resistance of the cheap cable was ridiculous... To the point where using the "dash" charger with the cheap cable only allowed the phone to say "charging slowly" (charging current <= 1A iirc) whereas the genuine cable said "charging rapidly" (~3A)

 

People often overlook the cables in a project thinking that they will all do as well as each other (not always the case)

 

Let me know what you decide in the end and how you get on though