Portrait Orientation

The Dot Matrix Display (DMD) is a 32x16 array of high-brightness LEDs for visually striking effects. [Product Page]
kellyw
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Portrait Orientation

Post by kellyw » Sun Oct 25, 2015 11:18 am

Just bought and trialed a red dmd and found that a single 32x16 display powered from auduino is not bright enough nor large enough to be seen from distance outdoors. I basically need to display a timer/clock with 3 digit display. I was planning to buy 2 more dmd and arrange them side by side in portrait orientation with each module displaying one large 16x32 digit.
It has been suggested here that arranging them in that fashion will seriously affect wide angle viewing.
Perhaps I could arrange 2 one on top of the other in landscape and another beside it in portraint orientation.
Anyone have any experience with different arrangements where the goal is to display a small number of very large characters/digits? I imagine this would be common for scoreboard style applications.

To solve the brightness problem I obviously need to power them externally. I don't have mains power and was considering a 12V car battery? Any other options I should consider? The system needs to operate for 3 hours. I've also read I need some form of 12v to 5v conversion device, ideally rated for 4A. I've also read that some of these devices can overheat. Does anyone have any concrete suggestions on a specific device (link?) that you've used successfully? (Jarcar would be ideal).

Finally, I need to mount the 3 boards together. I've read that the 4 small bolts protruding from the rear are designed for mounting. But they are very short and have no nuts. Again, any advice regarding mounting that people have actually used successfully?

Thanks!

Cheers Wayne.

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stryker
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Re: Portrait Orientation

Post by stryker » Sun Oct 25, 2015 11:50 am

Hi,

We use 4 DMDs arranged 2x2 in the landscape orientation as digital race track flags, displaying up to 3 characters to drivers moving at speed and the feedback has been universally good about the brightness and legibility. In fact we never drive them at 100% brightness even in daylight as we had complaints early on they were too bright. We dim them even more for night use too. We're using white rather than red though. This setup is powered via 110V mains so can't comment on running that specific project from battery to date.

I have another project (slowly progressing) which is actually a scoreboard. Again my intention will be to mains power them rather than try for battery as that will have even more DMD modules.

All the best with your project,
Geoff

angusgr
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Re: Portrait Orientation

Post by angusgr » Tue Oct 27, 2015 12:01 am

Hi Wayne,
kellyw wrote:Just bought and trialed a red dmd and found that a single 32x16 display powered from auduino is not bright enough nor large enough to be seen from distance outdoors. I basically need to display a timer/clock with 3 digit display. I was planning to buy 2 more dmd and arrange them side by side in portrait orientation with each module displaying one large 16x32 digit.
It has been suggested here that arranging them in that fashion will seriously affect wide angle viewing.
Perhaps I could arrange 2 one on top of the other in landscape and another beside it in portraint orientation.
Anyone have any experience with different arrangements where the goal is to display a small number of very large characters/digits? I imagine this would be common for scoreboard style applications.
This is probably possible, but our DMD and DMD2 software libraries don't support portrait orientations at present - they assume landscape mode.

As Geoff says, the brightness issue will go away (and then some!) after you have external 5V power. So perhaps 2 landscape DMDs horizontally stacked will be large enough, or failing that 4 in a 2x2 grid?
To solve the brightness problem I obviously need to power them externally. I don't have mains power and was considering a 12V car battery? Any other options I should consider? The system needs to operate for 3 hours. I've also read I need some form of 12v to 5v conversion device, ideally rated for 4A. I've also read that some of these devices can overheat. Does anyone have any concrete suggestions on a specific device (link?) that you've used successfully? (Jarcar would be ideal).
I haven't tested it, but something like this DC/DC converter should be suitable:
http://tronixlabs.com/power/dc-dc/dfrob ... australia/

Or you could use one of these for 2 DMDs:
http://www.ebay.com.au/itm/Carsmate-Wat ... h-R122W30w

If you end up using multiple DC/DC converters, join the 5V positive power outputs to separate DMDs but join the GND (-ve) outputs all together.
Finally, I need to mount the 3 boards together. I've read that the 4 small bolts protruding from the rear are designed for mounting. But they are very short and have no nuts. Again, any advice regarding mounting that people have actually used successfully?
The mounting bolts are M3 so you can use "M3 standoffs" (also called "M3 spacers") to extend them and get more length for mounting. You can get these from Jaycar among other places.

You can get either Nylon or metal spacers. Metal is stronger, but if you use metal just make sure to only contact the "solder masked" (green coated) parts of the DMD circuit board when you screw them down - or place a flat nylon washer at the base.


Angus

kellyw
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Re: Portrait Orientation

Post by kellyw » Wed Oct 28, 2015 6:00 am

Thanks Angus.

BTW, I wasn't having any trouble using the dmd library as I have created my own custom 32x16 digit font and was painting the pixels manually (as done within the dmd library implementation). I have however decided to go with a 2x2 landscape arrangement.

My main issue now is the voltage regulation. I have been looking at these two Jarcar options:
http://www.jaycar.com.au/Power-Products ... r/p/MP3478 rated for up to 5A for $39.95 or

http://www.jaycar.com.au/Power-Products ... t/p/MP3671 rated for 3A for $29.95

Would either of those be suitable? Would the options you suggest simply be cheaper? Would any of them need an attached heat sink? It's going to be used mostly at night, so I'm now also concerned that it may be too bright, so maybe the cheaper 3A option might be better in that respect?

Why might I need more than one power adapter? I was assuming I could run wires in parallel from a single power adapter to all 4 dmds and to the Arduino. Would that not work? Sorry - I'm good with software but know very little about electronics.

Cheers Wayne.

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Re: Portrait Orientation

Post by angusgr » Fri Nov 06, 2015 12:01 am

Hi Wayne,

Sorry for the delayed followup.
kellyw wrote: BTW, I wasn't having any trouble using the dmd library as I have created my own custom 32x16 digit font and was painting the pixels manually (as done within the dmd library implementation). I have however decided to go with a 2x2 landscape arrangement.
Oh, excellent!
kellyw wrote: My main issue now is the voltage regulation. I have been looking at these two Jarcar options:
http://www.jaycar.com.au/Power-Products ... r/p/MP3478 rated for up to 5A for $39.95 or

http://www.jaycar.com.au/Power-Products ... t/p/MP3671 rated for 3A for $29.95

Would either of those be suitable? Would the options you suggest simply be cheaper? Would any of them need an attached heat sink?
They both look like they would probably be suitable, maybe the only thing to check with Jaycar that the 5A/3A rating is achievable at 5V and not only when the output is set to 12V?

The options I suggested would be cheaper for just adapter, but there's an advantage to the jaycar ones just connecting into a cigarette lighter and probably requiring less custom wiring.
It's going to be used mostly at night, so I'm now also concerned that it may be too bright, so maybe the cheaper 3A option might be better in that respect?
I'd suggest using DMD2's brightness option to control the brightness directly from software to get the level you need.

You can't really rely on using a smaller adapter by itself to control the brightness, because it will only dim if it's overloaded - which might also cause it to overheat or switch off.

The "use a smaller adapter to dim" technique happens to work with USB ports because they have a lot of integrated overcurrent controls to elegantly handle the situation where they are overloaded, but we still don't recommend doing it. The technique doesn't necessarily transfer over to adapters like the ones we're discussing here.
kellyw wrote: Why might I need more than one power adapter? I was assuming I could run wires in parallel from a single power adapter to all 4 dmds and to the Arduino. Would that not work? Sorry - I'm good with software but know very little about electronics.
One adapter should be fine, as long as it can handle the output current. I suggested using two adapters because if you budget ~1A per display then a 3A supply won't be enough for all 4, but you could you use two 3A supplies where each supply drives 2 displays.

However, the 1A per display is really only if you drive all the LEDs on at once. If you're only displaying numbers (and especially if you use DMD2 library to dim the LEDs) then a single 3A supply should manage to power all 4.

Hope that makes sense - there's a few options we're discussing here so I can see it might be a bit confusing.


Angus

statbat
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Re: Portrait Orientation

Post by statbat » Tue Dec 22, 2015 10:56 am

kellyw wrote: BTW, I wasn't having any trouble using the dmd library as I have created my own custom 32x16 digit font and was painting the pixels manually (as done within the dmd library implementation).
Hello Wayne

I am also looking for portrait orientation.
Can you please share your library please.

Thanks
Cheers

statbat
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Re: Portrait Orientation

Post by statbat » Tue Dec 29, 2015 1:12 am

angelanavejas wrote:I have another undertaking (gradually advancing) which is really a scoreboard. Again my expectation will be to mains power them instead of strive for battery as that will have considerably more DMD modules.
I am also making a cricket scoreboard. But I want it to be for my cricket team only so it is not fixed but it is portable.
Plus I want the scoreboard to be updated automatically via internet from the scoring app which we use (cricketscorer.com.au)

So I have to rely on the portable power source. BTW do you see power sockets in the cricket ground. I dont see them at all.

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stryker
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Re: Portrait Orientation

Post by stryker » Tue Dec 29, 2015 1:41 am

angelanavejas wrote:I have another undertaking (gradually advancing) which is really a scoreboard. Again my expectation will be to mains power them instead of strive for battery as that will have considerably more DMD modules.
Perhaps we can compare notes? I've got my first PCBs back for a project which is a combo AFL/cricket scoreboard. Due to the number of DMD modules it will also need to be mains powered.

kellyw
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Re: Portrait Orientation

Post by kellyw » Sun Jan 03, 2016 6:30 am

With respect to how to do portrait orientation ...

Firstly, I'm not actually using portrait any more due to the asymetric physical structure of the DMD which limits the view angle from the left or right if oriented in portrait fashion. I'm now using 2x2 boards with extra large digits that span 2 boards vertically (readable from 100 meters).

In both case, I only needed digits 0 .. 9 (for time display), so I created my own bitmap font; stored it in an array in bit compressed format and then used it to paint individual pixels.

With respect to portable battery power, I'm now successfully using 2 x 9v car battery. One battery is connected via a 5v voltage regulator to each of the DMD boards. The other battery is connected directly to the Arduino (using Arduino's built in voltage regulator).

When I originally tried powering both from the same car battery, the DMDs quickly sucked enough power out of the car battery that the Arduino shut down due to low voltage. Now that I'm using 2 separate car batteries, the Arduino uses hardly any power and so maintains a high voltage. The car battery attached to the DMDs drops in voltage during use, but that simply means the DMDs dim slightly. Works successfully for 3 hour of competition, then I recharge during the week for use the following weekend.

Cheers, Wayne.

statbat
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Re: Portrait Orientation

Post by statbat » Sun Jan 03, 2016 3:28 pm

kellyw wrote: With respect to portable battery power, I'm now successfully using 2 x 9v car battery. One battery is connected via a 5v voltage regulator to each of the DMD boards. The other battery is connected directly to the Arduino (using Arduino's built in voltage regulator).

When I originally tried powering both from the same car battery, the DMDs quickly sucked enough power out of the car battery that the Arduino shut down due to low voltage. Now that I'm using 2 separate car batteries, the Arduino uses hardly any power and so maintains a high voltage. The car battery attached to the DMDs drops in voltage during use, but that simply means the DMDs dim slightly. Works successfully for 3 hour of competition, then I recharge during the week for use the following weekend.
Thanks for your input.
I think I can try to run it with 1 car battery. 1 car battery for DMD and I can run arduino with 6 AA batteries.
Saw so many Youtube videos where people are running arduino with AA batteries.

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