Using 4 pcs. of 16x24 red LED matrix (item no. 555)

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odometer
 
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Re: Using 4 pcs. of 16x24 red LED matrix (item no. 555)

Post by odometer »

Here is a copy of the information from when I ordered the incorrect power supply:
Order Confirmation No: 246918‏
Adafruit Industries ([email protected])
3/03/13
To: [e-mail address redacted]


Order Confirmation from Adafruit Industries

Thanks for shopping with us today!
The following are the details of your order.
------------------------------------------------------

Products
------------------------------------------------------
1 x 5V 2A (2000mA) switching power supply - UL Listed[ID:276] = $9.95
------------------------------------------------------
Sub-Total: $9.95
Sales Tax: $0.00
United States Postal Service (0.34lbs) (First-Class Mail incl. $0.75
insurance): $4.33
Total: $14.28
Today I am going to send it back.
I await delivery of a power supply with adequate voltage. Your product #798 seems to be such a product.

By the way, why was an inadequate power supply recommended to me in the first place? I didn't think to look up the correct voltage, because I figured you guys knew what you were doing.

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adafruit_support_bill
 
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Re: Using 4 pcs. of 16x24 red LED matrix (item no. 555)

Post by adafruit_support_bill »

Mr Odometer. The 5v power supply recommended is the correct supply for these 5v displays.
The board can operate on an external supply of 6 to 20 volts.
That is the specification for the Arduino - not for the displays. If you are trying to power the displays from the 5v pin of your Arduino, you will overload the voltage regulator on your Arduino.

odometer
 
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Re: Using 4 pcs. of 16x24 red LED matrix (item no. 555)

Post by odometer »

adafruit_support_bill wrote:Mr Odometer. The 5v power supply recommended is the correct supply for these 5v displays.
Then where does it (the power supply) connect to?
It ends in what I believe called a "barrel connector" (it is a sort of hollow cylindrical shape).
How was I supposed to hook it up?

If you look at the photos in the tutorial here
http://ladyada.net/products/16x24LEDmatrix/
you see essentially the procedure I followed as far as power is concerned.
And the words in the tutorial say nothing to contradict it.

The one thing I did differently was use long IDC cables rather than short ones. That was because, for my application, the short cables are too short to reach.

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adafruit_support_bill
 
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Re: Using 4 pcs. of 16x24 red LED matrix (item no. 555)

Post by adafruit_support_bill »

OK. Let's discuss voltage regulators:

The Arduino has a linear voltage regulator. It needs about 2v of 'headroom' to regulate - hence the 7-12v requirement for an "external supply".

As a linear voltage regulator, it needs to burn off the excess voltage as heat. So if you power your Arduino with the stock 9v wall-wart, close to half the energy that goes in needs to be dissipated as heat. Now this is fine if you are just powering an Arduino and a few leds. But as you start to load things down more, the regulator will get extremely hot and eventually burn out. That is why I would not recommend powering 4 panels from the Arduino regulator.

So there are 2 ways to approach this:
1) Power the Arduino with a 9v wall-wart or similar supply and power the Panels from the 5v/2A external supply (just be sure to tie the grounds together.)
2) Bypass the Arduino supply and power the whole thing from your 5v/2A supply. To do this, you would wire the 5v/2A power supply to both your panel and the Arduino. But you would connect it to the 5v and GND pins of the Arduino instead of to the DC barrel jack.

Usually I do this by cutting off the barrel connector and splicing on some wires with pins. But you can also use one of these: http://www.adafruit.com/products/368

odometer
 
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Re: Using 4 pcs. of 16x24 red LED matrix (item no. 555)

Post by odometer »

adafruit_support_bill wrote:So there are 2 ways to approach this:
1) Power the Arduino with a 9v wall-wart or similar supply and power the Panels from the 5v/2A external supply (just be sure to tie the grounds together.)
2) Bypass the Arduino supply and power the whole thing from your 5v/2A supply. To do this, you would wire the 5v/2A power supply to both your panel and the Arduino. But you would connect it to the 5v and GND pins of the Arduino instead of to the DC barrel jack.

Usually I do this by cutting off the barrel connector and splicing on some wires with pins. But you can also use one of these: http://www.adafruit.com/products/368
I wish you had told me this sooner.
2) The displays will be the biggest current consumers. But the panels are multiplexed, so it is not as if you are driving all the LEDs simultaneously. Figure 16 LEDs @20 mA times 4 panels is 1280 mA. So the 5v 2A power supply should handle it.
That would have been the right time to tell me.
What I understood you to mean was, "Use XXX power supply", not "Get one of XXX power supply, cut it up and then use it".

I am reminded of this scene:
http://www.youtube.com/watch?v=QyCp3gklrH0&t=03m28s
(watch for about 15 seconds)

cjansen
 
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Re: Using 4 pcs. of 16x24 red LED matrix (item no. 555)

Post by cjansen »

Take a look at this picture, This is powered by the Arduino UNO.
http://www.cjansen.net/images/Arduino/date_time.JPG
I do not recommend this, but it is working without a glitch, and if you buy a 5V 2AMP power supply you can buy the PID373 with it and power your displays with this to the IDC ribbon cable.

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adafruit_support_bill
 
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Re: Using 4 pcs. of 16x24 red LED matrix (item no. 555)

Post by adafruit_support_bill »

Take a look at this picture, This is powered by the Arduino UNO.
That font has relatively few leds illuminated at a time so it will require less power than the patterns used by the OP.

odometer
 
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Re: Using 4 pcs. of 16x24 red LED matrix (item no. 555)

Post by odometer »

adafruit_support_bill wrote:
Take a look at this picture, This is powered by the Arduino UNO.
That font has relatively few leds illuminated at a time so it will require less power than the patterns used by the OP.
What's the point of spending $25 per display unit if you can't make pretty patterns?

odometer
 
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Re: Using 4 pcs. of 16x24 red LED matrix (item no. 555)

Post by odometer »

My father and I spend quite a few hours on the case. We only did the front, top, and sides, though, not the back.

Here's the front of the clock. (Please ignore the white wire in the background; it's to power something else.)
clock_front.jpg
clock_front.jpg (143.08 KiB) Viewed 612 times
Here are the clock guts. The Arduino board is just scaffolding; I intend to replace it with a Boarduino.
clock_guts.jpg
clock_guts.jpg (94.89 KiB) Viewed 612 times

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