180 LEDs

[justDIY]

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

right now I'm thinking about eight shift registers per color, that'll give me 64 bits, 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.

[minimum]

What about Maxim's 20/28 port expanders: MAX6956 and MAX6957 ?

[justDIY]

The cost of those port expanders is the main drawback.  Phillips has some 32 bit serially connected port expanders, they are tri-state logic gates like the maxim chips, but again, they cost a LOT more than the humble 595.

I want to build a larger version of my "Rainbow Chaser" and use it as a clock

[cadstarsucks]

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

right now I'm thinking about eight shift registers per color, that'll give me 64 bits, 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.

A matrix of 3 74ABT595s and 8 columns will do it for you.

Dan

[justDIY]

I'd posted this topic on a larger forum and that was the suggestion I got back:

so right now I'm looking at using eight 595's driving the common leg of the rgb leds (60 pins and bits total), and 4017 with some transistors to drive the discrete legs.  the discrete legs are wired in parallel, grouped by color.  q3 of the 4017 is tied to reset so it only counts 0, 1, 2, repeat.  the clock of the 4017 is driven by the latch clock of the 595's

I'm going to try dividing the project into four quadrants, each with identical driver boards, which link together.  this should help to minimize the amount of wire going everywhere.

[cadstarsucks]

I'd posted this topic on a larger forum and that was the suggestion I got back:

so right now I'm looking at using eight 595's driving the common leg of the rgb leds (60 pins and bits total), and 4017 with some transistors to drive the discrete legs.  the discrete legs are wired in parallel, grouped by color.  q3 of the 4017 is tied to reset so it only counts 0, 1, 2, repeat.  the clock of the 4017 is driven by the latch clock of the 595's

I'm going to try dividing the project into four quadrants, each with identical driver boards, which link together.  this should help to minimize the amount of wire going everywhere.

Well I have use this design for production displays for years and it remains the most cost effective still...Although I did not get the part right in the previous post.

Dan

[cadstarsucks]

I'd posted this topic on a larger forum and that was the suggestion I got back:

so right now I'm looking at using eight 595's driving the common leg of the rgb leds (60 pins and bits total), and 4017 with some transistors to drive the discrete legs.  the discrete legs are wired in parallel, grouped by color.  q3 of the 4017 is tied to reset so it only counts 0, 1, 2, repeat.  the clock of the 4017 is driven by the latch clock of the 595's

I'm going to try dividing the project into four quadrants, each with identical driver boards, which link together.  this should help to minimize the amount of wire going everywhere.

I had not realized this before... I am the one that answered you  on the other forum

Dan

[justDIY]

small world syndrome!

[cadstarsucks]

small world syndrome!

Sure is...I stumbled on to that one looking for something else.  The moderator did not like having someone there not afraid to help people more than he could.

Dan

[thenewton]

hi
i think u should try as the cad has mensioned bcaz in my opinion that will also work better