LED staircase runway
Steve Rennells
Posts: 40
This is a project I'm working on for my daughter; any comments/ideas/suggestions would be greatly appreciated.
Overview: Staircase “runway” LED display using IR emitter/detectors to trigger LED’s.
Twelve banks of two LED’s (one LED on each side of each step of the staircase). Each step also has an IR emitter/detector. When a beam is broken, the pair of LED’s for that step is illuminated, and the LED pair one step above and one step below also are illuminated, but dimmed. The idea is to have the LED’s follow her up/down the stairs.
Stamp Model Used – Homework Board
I plan on breaking this project down into segments, and working on one segment at a time.
The first step is gaining control over each bank of LED’s using as few stamp I/O pins as possible. Initially I’ll trigger the LED’s programmatically, and then I’ll begin working on the IR triggers.
I’ve been searching through previous posts and have found several examples of LED display controls using 74HC595’s, or MAX7219’s, and I’m unsure at this point which option would be better for my application.
EDIT: I knew I had seen I/O expansion referenced somewhere in the Parallax documentation - just found it in StampWorks - looks like the 595's and 165's will solve my I/O issues. /END EDIT
I need to reserve I/O pins for the twelve IR triggers. I’ve found recommendations for the CDP68HC68P1 and the PCA9535 to expand the Stamps I/O’s.
I have some concerns regarding the length of wire needed, its inherent resistance, and the power supply requirements as well. As you can probably tell, I haven’t really started working on this yet, still just mulling everything around in my head. I need to get some measurements of the staircase so I know the lengths of wire needed and can then work out some of these details. Another determining/limiting factor would be the voltage/current requirements of the LED’s and IR, and whether the Homework board can provide the necessary power to the circuit.
Sorry I don't have any real specifics on this yet, I'm just looking for general ideas/comments on the concept. Maybe I should just scrap this one and go build a robot . . .
Cheers,
Steve
Post Edited (Steve Rennells) : 11/16/2005 11:47:11 AM GMT
Overview: Staircase “runway” LED display using IR emitter/detectors to trigger LED’s.
Twelve banks of two LED’s (one LED on each side of each step of the staircase). Each step also has an IR emitter/detector. When a beam is broken, the pair of LED’s for that step is illuminated, and the LED pair one step above and one step below also are illuminated, but dimmed. The idea is to have the LED’s follow her up/down the stairs.
Stamp Model Used – Homework Board
I plan on breaking this project down into segments, and working on one segment at a time.
The first step is gaining control over each bank of LED’s using as few stamp I/O pins as possible. Initially I’ll trigger the LED’s programmatically, and then I’ll begin working on the IR triggers.
I’ve been searching through previous posts and have found several examples of LED display controls using 74HC595’s, or MAX7219’s, and I’m unsure at this point which option would be better for my application.
EDIT: I knew I had seen I/O expansion referenced somewhere in the Parallax documentation - just found it in StampWorks - looks like the 595's and 165's will solve my I/O issues. /END EDIT
I need to reserve I/O pins for the twelve IR triggers. I’ve found recommendations for the CDP68HC68P1 and the PCA9535 to expand the Stamps I/O’s.
I have some concerns regarding the length of wire needed, its inherent resistance, and the power supply requirements as well. As you can probably tell, I haven’t really started working on this yet, still just mulling everything around in my head. I need to get some measurements of the staircase so I know the lengths of wire needed and can then work out some of these details. Another determining/limiting factor would be the voltage/current requirements of the LED’s and IR, and whether the Homework board can provide the necessary power to the circuit.
Sorry I don't have any real specifics on this yet, I'm just looking for general ideas/comments on the concept. Maybe I should just scrap this one and go build a robot . . .
Cheers,
Steve
Post Edited (Steve Rennells) : 11/16/2005 11:47:11 AM GMT
Comments
Here are some thoughts on just the power distribution, which I think will work. Rather than bringing a FIRE HOSE sized cable to feed this baby, and possibly multiple transformers to drop down the voltage to levels that the LEDs can handle, I'd consider doing something like the following. The analog gurus can pass on whether it's actually doable.
I'd use a multiple conductor cable, and a feeder voltage which is evenly divisable by the voltage required by the LEDs. Let's say the LED voltage should be 2.4 volts. Run 24 volts through each cable, and terminate the cable with a set of parallelled resistors. I supppose you'd end up with 10 resistors here, but I leave that to the "experts".
Then I'd use this n-way voltage divider to feed each LED grouping. Each single conductor in the multi-conductor cable now only needs to carry a part of the amperage load. The load on each conductor will be total LED load / number of conductors. Now, instead of having to use a (say) 16 gauge 2 conductor cable, you can use a (say) 28 gauge 8 conductor cable.
There may even be an optimal number and grouping method for your particular scheme which will allow some part of the control system to be at or near this feeder termination location. The dimming function comes to mind.
Regards,
Bruce Bates