180 leds! - Electronic Circuits Projects Diagrams Free

justDIY · 7th February 2007, 05:51 PM

I need some recommendations for ways to discretely control 180 leds. what I want to build is a circle, circumscribed with 60 RGB leds (180 leds total) .

right now I'm thinking about eight shift registers per color group, that'll give me 64 channels, times three, for a total of 192. I seem to recall seeing a 32 bit shift register from MAXIM or maybe it was someplace else - probably cost more than 8 74hc595's would cost.

I'm thinking I'll make up a circuit board to hold the 24 shift registers, and then use headers / cable harness to wire up the leds. Or I might need to make three circuit boards, with just 8 registers each - it depends how messy the routing becomes.

I'm wondering how to calculate the update rate I can expect shifting out 192 bits of data with a 20mHz pic.

Is there an easier way I'm overlooking? I thought about some sort of multiplexing or matrix building, but the leds kinda prevent that - they'll either be common anode or common cathode depending on the cost from the supplier.

**Nigel Goodwin** · 7th February 2007, 08:20 PM

The data rate won't be a problem, you can shift data far faster than you require with a much slower device. For a simple multiplexing, how about having 60 outputs from the shift registers, and switch (multiplex) between the three colours?. It's not a minimum output solution, but you're not really looking for that - and it's simple.

justDIY · 7th February 2007, 09:48 PM

that sounds like a great plan ... certainly 8 registers is better than 24! Three of the remaining four bits of the 64 bit register could even be used to control which color group was active.

**Nigel Goodwin** · 8th February 2007, 07:52 AM

Quote:

Originally Posted by justDIY

that sounds like a great plan ... certainly 8 registers is better than 24! Three of the remaining four bits of the 64 bit register could even be used to control which color group was active.

I'm a big believer in keeping things simple!

jrz126 · 8th February 2007, 06:47 PM

How much current are you looking to run through each LED?

You may want to look at something like this (if you havent already): http://focus.ti.com/docs/prod/folder...t/tlc5940.html
Those would even allow you to dim each LED and stuff. Plus you can get free samples.

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7th February 2007, 05:51 PM	(permalink)
justDIY	180 leds! I need some recommendations for ways to discretely control 180 leds. what I want to build is a circle, circumscribed with 60 RGB leds (180 leds total) . right now I'm thinking about eight shift registers per color group, that'll give me 64 channels, times three, for a total of 192. I seem to recall seeing a 32 bit shift register from MAXIM or maybe it was someplace else - probably cost more than 8 74hc595's would cost. I'm thinking I'll make up a circuit board to hold the 24 shift registers, and then use headers / cable harness to wire up the leds. Or I might need to make three circuit boards, with just 8 registers each - it depends how messy the routing becomes. I'm wondering how to calculate the update rate I can expect shifting out 192 bits of data with a 20mHz pic. Is there an easier way I'm overlooking? I thought about some sort of multiplexing or matrix building, but the leds kinda prevent that - they'll either be common anode or common cathode depending on the cost from the supplier. __________________ If you don't have a planet, what good are gold bars? want to contact me directly? gmail gordonthree check out my project website: http://projects.dimension-x.net Favorite numbers: 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

7th February 2007, 08:20 PM	(permalink)
Nigel Goodwin	The data rate won't be a problem, you can shift data far faster than you require with a much slower device. For a simple multiplexing, how about having 60 outputs from the shift registers, and switch (multiplex) between the three colours?. It's not a minimum output solution, but you're not really looking for that - and it's simple. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

7th February 2007, 09:48 PM	(permalink)
justDIY	that sounds like a great plan ... certainly 8 registers is better than 24! Three of the remaining four bits of the 64 bit register could even be used to control which color group was active. __________________ If you don't have a planet, what good are gold bars? want to contact me directly? gmail gordonthree check out my project website: http://projects.dimension-x.net Favorite numbers: 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

8th February 2007, 06:47 PM	(permalink)
jrz126	How much current are you looking to run through each LED? You may want to look at something like this (if you havent already): http://focus.ti.com/docs/prod/folder...t/tlc5940.html Those would even allow you to dim each LED and stuff. Plus you can get free samples. __________________ Jeff Zimmerman To the optimist, the glass is half full. To the pessimist, the glass is half empty. To the engineer, the glass is twice as big as it needs to be.