View Full Version : Project Recommendations

01-14-2012, 07:16 PM
Hello All, I am building a project that will incorporate approximately 80-90 LED's broken up into smaller parallel circuits, each blinking at different speeds.My current plan has 8 separate LED circuits with the largest circuit having 21 LED's that I want to light simultaneously. The other 7 circuits will light the LED's in their respective circuits individually. The plan is to have each of the 8 circuits run in a continuous loop. I have 2 questions before moving forward.

1) Is it possible to control 80-90 LED's using a micro controller?

2) If so what product or products would best fit my application?

Thank you in advance.

Ken Gracey
01-14-2012, 07:29 PM

I don't have the answers you're looking for just yet, but I'm sure you'll get some interesting replies from people who have done exactly that. I'd probably start with some Google research since controlling LEDs is so popular. Might be good in the meantime to let us know if you're using a BASIC Stamp or Propeller, or if that's still an open topic. The Propeller's multicore design could make concurrent control quite easily.

The reason I'm replying is because I want to be the first to welcome you to our forums. Welcome to the Parallax forums! You'll find lots of very capable people on these forums who are pleased to help. Always feel comfortable asking any question you wish, along the way.


Ken Gracey

Duane Degn
01-14-2012, 07:45 PM
Let's see if I can finish this post in time to be the second person to welcome you.

First off:
1) Yes, a uC can easily control 90 LEDs. I have a project with 120 LEDs controlled by a Propeller.
2) IMO The Propeller is the best choice. You'll also want some 595 shift registers (probably) to help control the LEDs.


I think I used 16 shift registers in the above LED array. Each LED can be controlled individually with 8-bits of brightness control. The picture shows it outputing the image aquired by the small B&W video camera in the top left corner.

I'll look around for some good links and post them here.

01-14-2012, 07:50 PM
Thank you Ken for the warm welcome! I was hoping to use a BS1 module I have laying around but after playing with it have recognized it's limitations.

01-14-2012, 07:51 PM
Thank you Duane for the warm welcome! I greatly appreciate your input! Thanks again.

Duane Degn
01-14-2012, 08:06 PM

Here's a little list of my top picks for parts.

My current favorite Propeller board it the QuickStart (http://www.parallax.com/Store/Microcontrollers/PropellerDevelopmentBoards/tabid/514/CategoryID/73/List/0/SortField/0/Level/a/ProductID/748/Default.aspx). It gets power from the same USB cable used to program it. It makes it really easy to test a new device or a piece of code. I usually have three or four within arms reach.

Here are few more Propeller board favorites.

Gaget Gangter Board
(http://www.parallax.com/Store/Microcontrollers/PropellerDevelopmentBoards/tabid/514/CategoryID/73/List/0/SortField/0/Level/a/ProductID/711/Default.aspx)Propeller Protoboard USB
(http://www.parallax.com/Store/Microcontrollers/PropellerDevelopmentBoards/tabid/514/CategoryID/73/List/0/SortField/0/Level/a/ProductID/674/Default.aspx)Propeller Protoboard
The Protoboards are also available individually but I always take advantage of the multi-board deals.

I use these shift registers (http://www.parallax.com/StoreSearchResults/tabid/768/List/0/SortField/4/ProductID/229/Default.aspx?txtSearch=shift+register). (If you're buying a bunch of them it might be cheaper to get them at Digi-Key.)

You'll probably want some bare proto boards too.

Parallax's protoboard (http://www.parallax.com/Store/Microcontrollers/PropellerDevelopmentBoards/tabid/514/CategoryID/73/List/0/SortField/0/Level/a/ProductID/682/Default.aspx)is inexpensive.

But some times the ground plain and power buses gets in the way (on the Parallax board). If you're attaching a bunch of LEDs to one board, (like the array I made) I'd suggest using SparkFun's protoboard (http://www.sparkfun.com/products/8619). (Just don't tell Ken I said so.) There's also cheaper "perf board" available which is good for some uses (but I used the SF stuff for my array).

Here's a driver (http://obex.parallax.com/objects/437/) for the 595 chips. I ended up making my own driver for the array I posted earlier. Mine is not really a general purpose driver but I'll share it if you want to look at it. (I'm pretty sure it's posted somewhere on the forum.)

There's something very fun about a bunch of LEDs. I haven't figured out what it is yet that make it so fun to control and watch a bunch of LEDs going on and off.

01-14-2012, 09:11 PM
Duane, Please forgive me for my ignorance. Could you explain why the Propeller would work better than a Stamp? I have experience with the Basic Stamps but would need to educate myself on the Propeller.

Mike Green
01-14-2012, 09:40 PM
You could do your project with a Stamp, but the programming would be trickier. The Stamp can only do one thing at a time and creating overlapping loops to blink LEDs at different rates and with different patterns is not straightforward. It's doable, but not straightforward.

The Propeller naturally handles multiple overlapping tasks since it has 8 separate processors. Each processor is also fast enough to handle multiple tasks using the same sort of techniques you'd have to use with a Stamp, but, with the larger memory and the speed, this would easier than with a Stamp.

You might look at the TPIC6595 from TI. It works just like a 74HC595, but includes MOSFET power transistors on its outputs, so you could drive multiple LEDs directly

Duane Degn
01-14-2012, 10:03 PM
Duane, Please forgive me for my ignorance. Could you explain why the Propeller would work better than a Stamp? I have experience with the Basic Stamps but would need to educate myself on the Propeller.

As Mike says, being able to do more than one thing at a time makes a huge difference in a lot of projects. The Prop really shines in robotics.

The shift register (http://www.sparkfun.com/products/734)Mike mentioned is little different than normal 595s. It can handle larger currents but it can only sink current not source current (assuming a TPIC6595 is the same thing as a TPIC6B595). So you'd want to have them on the cathode side of the LEDs.

If you're using relatively low current LEDs then the regular 595 shift registers should be okay.

Edit: I linked to a TPIC6B595 which appears to be a lower powered version of the TPIC6959 (6959 datasheet link (http://www.ti.com/lit/ds/slis010b/slis010b.pdf)). I've only used the "B" version myself. I think both versions can only sink current. 250ma continuous for the 6595 and 150ma continuous for the 6B595.