Chained DMDs on low power?

The Dot Matrix Display (DMD) is a 32x16 array of high-brightness LEDs for visually striking effects. [Product Page]
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bwooce
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Joined: Mon May 28, 2012 11:15 am

Chained DMDs on low power?

Post by bwooce » Fri Jul 27, 2012 1:07 pm

Hi,

Just a quick question -- are multiple chained DMDs supposed to work when connected to USB power (via a Freetronics Eleven)?

The first one lights up okay, but the second doesn't. I *think* I've got the link cable connected correctly.

Both DMDs work fine independently. Also curiously, they've got different PCB layouts.

Thx,
Bruce

Aussie_Wombat
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Location: Adelaide, South Australia

Re: Chained DMDs on low power?

Post by Aussie_Wombat » Sun Jul 29, 2012 12:29 am

The usb will only power one dmd. To power 2 or more you need an external power supply. 5V 4A should suffice...

bwooce
Posts: 21
Joined: Mon May 28, 2012 11:15 am

Re: Chained DMDs on low power?

Post by bwooce » Sun Jul 29, 2012 1:04 pm

Thanks Wombat. I think I had the plugs wrong on the extension link -- I've created some new IDC cables and they worked first time off USB. It's not bright, but does mostly work with a few flickering pixels. 2 is deffo the limit though.

The included cable seems to transpose pin 1? I'm new to IDC connectors, but it looks like the supplied cable enters the connector from different sides?

Can you help me identify the true 1:1 PIN mapping from Computer->Input and Output->Input?

Is it always top-left pin => top-left pin in terms of direct electrical connection? There's not much of a guide for daisychaining them.

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Simon
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Re: Chained DMDs on low power?

Post by Simon » Mon Jul 30, 2012 2:33 am

Aussie_Wombat wrote:The usb will only power one dmd. To power 2 or more you need an external power supply. 5V 4A should suffice...
My scoreboard project (EtherTen) works fine with 2x DMDs running off USB, but forget trying to use the ethernet at the same time - brownout city ;)

But then this is running off a Macbook Pro which have at least one port capable of supplying higher-than-normal current.

Aussie_Wombat
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Location: Adelaide, South Australia

Re: Chained DMDs on low power?

Post by Aussie_Wombat » Mon Jul 30, 2012 3:39 am

Thanks Simon. I forgot about that.

I have 6 dmd's at home, in a 2x3 configuration. I will check out the daisy chain plan when I get home.

As for the idc cable connection. The red stripe on the edge generally denotes the side which pin 1 is on. The block on the idc plug denotes the side that pin one is on. Anyone correct me if I am wrong...

Cheers Dennis aka Wombat

Aussie_Wombat
Posts: 51
Joined: Tue May 22, 2012 12:52 pm
Location: Adelaide, South Australia

Re: Chained DMDs on low power?

Post by Aussie_Wombat » Mon Jul 30, 2012 11:47 am

Daisy Chain Reply in this post

viewtopic.php?f=26&t=912&p=2510#p2510

Cheers Aussie_Wombat

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