Got an idea in mind for a 300 LED chaser that runs down the side of a pinewood derby track. I'm trying to do this with a minimum wire count, and a lack of controller required. I have some sort of hint in my head at doing this using some sort of staged toggle, that one LED turns on, and enables something that the next pulse turns on the new LED down the chain, which then enables the gate for the next LED down the chain...I don't know. Thoughts? Ideas? I'm looking to build this as a 3/4" wide strip 36' long. Cheers.

 

Have you read this article?

LEDs, 555s, Flashers, and Light Chasers

There are so many ways to do this that it would be hard to cover them all.

A shift register might do what you want, a simple type D flip flop that passes the data (the lit LED every clock pulse), which would be simple.

Or a series of monostables feeding down a line. Trigger one, when it times out it triggers the next one, and so on.

Both the latter are expensive, 300 parts are going to add up.

I suspect the Type D shift register (look for CMOS ICs with lots) is the least expensive.

If you need details, just ask.

 

Just comparing two chips, 4017 & SR 74C164; it would take the same number[38] but the 4017 would require much more wire and seven AND gates. With the 74C164 you would load a 1 into the first stage for the first count, then load 0 thereafter. The 8th output of each stage is serial input to next stage.Outputs should drive a LED @ 8 mA , with all cathodes tied together with one 1k+-to ground,depending on LED used. Can use V at 1k to detect if more than "1" is circulating or when full count is reached. Still have about 6 wires going full length, +,- ,reset, LED current, clock, & inter-connections.

 

I know you don't want to use a microcontroller, but it will be the most effective solution for your project.
My recommendation:
If the strip is going to be 3/4" wide, you can easily have a 4 wire bus (I2C(+V, GND, SDA, SCLK)) that runs down the backside which will connect to I2C I/O expanders (typically 8-bit). Each port of the I/O expander gets its own LED.
This way, by using the I2C bus, you can control each individual LED (have any type of display program of your choice).
The cost shouldn't be too bad: (1 Host micro: $4-8), (300/8 = est. 38 I/O expanders : $39), (300 LED's: $ est. $10)..............with a budget of $60 a very nice display can be made.

One thing to keep in mind with I2C IC's is that some have the ability to let you program their address, this will be an important factor to consider if building the device, so that there isn't any bus conflicts when you go to address LED's.

Anyways, have fun!

 

Microcontroller has the same problem as the rest, he wants to get rid of the wires.

It is expensive, but it is possible to build a bunch of repetitious modules, each with 2 power supply leads, signal in, signal out, and possibly a clock circuit, so only 5 wires go down the track (and don't forget the LED wires, possibly 1 on each side).

I don't see how a microcontroller would be more efficient, especially if you're having to do the repetitious module routine.

3¢/LED is a bit optimistic too, not if you want good ones. Figure about double that.

Something like a 4015 could handle 8 LEDs, BGMicro cost 25¢, or a 4013 can handle 2, (again 25¢). You'll need transistors to drive the LEDs too.

Guess right now we're waiting for the OP.

 

If you just want something really simple, you could get a "movie marquee" effect using a 555 timer, a 4017 Johnson counter, a few diodes, a few transistors, driver ICs and lots of LEDs and current limiting resistors.

If you will be running it from a regulated 12v supply, you could run several red, yellow or green LEDs in series per current limiting resistor. Red LEDs usually have lower Vf (forward voltage) than other visible colors.

The marquee sequenced would go something like this:
011
110
101
...etc
or:
0011
0110
1100
1001
...etc
Those are basic blocks of three or four LEDs. The rest of the LEDs would be wired to light in the same pattern, and laid end to end. It would create an illusion of movement either up or down the entire track.

 

Hadn't thought of that, I was focused on the ripple down effect.

Still, it is a bunch of descrete modules. This seems to be where this project is going. Wonder if it will get built?

 

Yeah, it'll take a number of modules, with at least one control module. Our OP's biggest expense will probably be getting the module boards from a PCB house. It'll be tedious soldering in all those LEDs. They'll have to do some searching to find wide-angle view LED's at a decent price, too.

Nearly all of the LEDs offerred on auction sites are narrow view, and wouldn't work well at all for his application.

 

Hello,

I do not know waht budget he has for the leds, but I use TELUX leds.
http://nl.farnell.com/jsp/search/br...ensearch_001&Ntt=telux&Ntx=&_requestid=760018
These have a nice intensity and a view of 90°.
They also have a nice flat way of mounting.

Greetings,
Bertus

 

Well, even a 90° viewing angle isn't wide enough, I'm afraid. Unless people were standing very close to the track, they wouldn't see the LEDs light up. Something more like 130° could work.

 

Hello,

What color should the leds be?
Here is a 130° 1.1lm white led. Also in a kind of TELUX housing.
http://nl.farnell.com/cree/lp368pwn1-d0g-00001/led-p4-white/dp/1649015?_requestid=760946

Greetings,
Bertus

 

Sorry for not getting back to this post sooner. I actually didn't expect so many responses so quickly.

I kind of like the idea of the microcontroller using the io expanders. It does seem like it would be fairly simple. My only concern with using a microcontroller was that I have NO idea about multiplexing LEDS (and was concerned about a high wire count), and had no idea that these IO expander modules even existed.

The kids end up sitting between 4 and 20' away from the track, so anyone towards the back will have a good full view of medium angle LED's that get used. Even for the kids only 4' away, with LED's so close together, they will still see quite a large section of LED's.

The track is going to be broken down into 6' segments, so if I space the LED's at 1.5" apart, then I end up with 48 LED's per section.

If I go with 6 sections, then I have 36' of track, 288 LED's, and 36 expanders.

If I go with 7 sections of track, then I end up with 42' of track, 336 LED's, and 42 expanders.

Further thoughts? Will 336 LED's be any more difficult to access/control that 288 LED's?


Edit: I don't really have much in the way for colour consideration. White may not be sufficiently contrasting against the track (which will be painted white). Maybe red, or blue, or even green? Probably not high intensity ones either, as looking directly at those can be quite blinding.

 

High intensity isn't the issue, it is field of view. You might be able to take high intensity and disperse them with lenses or some other scheme.

Power requirements will be quite modest too, depending on how many LEDs are lit at a time. The switching circuits will be very low power. Figure 40ma per LED lit (actually it is 20ma, but you need some fudge factor to increase the reliability).

The actual numbers of LEDs is more dependent on your pocket book than technical issues. Depending on costs and parts count this could be under $100, or up to a $1,000.

Since you're buying quantity you have the opportunity to save money by some dickering for quantity discounts.

 

Regarding IO expanders, are there any specific ones that are easiest to use? I'm looking at this part: MCP23S08-E/P from Mouser, mostly because it's cheapest. I see that it can only handle 25mA of current on each io pin, and 125mA on VDD to the chip. Are there other ones out there that can drive more, or am I looking at transisitors to drive my LED's no matter what?

 

A bit of a crazy idea: Imagine a tiny logic NC7SZ14 schmitt trigger across a pair of wires. Add a resistor from plus to the input and a cap to ground such that when power is applied, the gate starts out high then quickly switches low. The LED and resistor are on the output of the gate to ground so the LED flashes briefly. The output also pulls the gate of a P-channel mosfet low, turning it on, passing the power on to the next circuit (source to input power, drain to output power). The last output is shorted to ground so that the power source can sense the system short and reset using an ordinary resetting electronic breaker circuit. Each LED needs a mosfet and gate but it has the advantage of just two wires in and out. I suppose the mosfet needs to have a pretty low on resistance since 300 are in series. If they made 4000 series in tiny logic then the system could operate at a higher voltage in current-limit mode.

 

300 LEDs without controller? Good luck.

you could use a 16F59- each can control 16x6 LED with multiplexing the ports 6x = 96 LEDs.
You could make it 17x6 so you need 3 chips. And its a lot of wiring work, 102 LEDs each into a X/Y matrix.
Basically you need 24 wires running with your LEDs altough it can be very thin magnet wire.

 

I thought I'd see if my idea would work without the gate. I just used typical mosfets I found in LTSpice. I'm switching the negative rail so that n-channel mosfets will work. Since it's just mosfets, it should be possible to use a higher voltage and current limit. That would overcome the series fets' resistance and give each LED the same current. At the end, I'd have a short and the driver circuit would monitor the voltage to watch for the short. Then the driver circuit would turn off the voltage for a short period to reset the system. Maybe discharge resistors are needed for the caps for reset.

 

Hello,

Did anyone notice that this thread is MORE than 5 years old?

If you want to discuss this topic, start a new thread.

Bertus

 

Nope. This came up under "new posts." Newbie here. : )
Wish there were a "new thread" tab.

 

Hello,

It happened to get in the new posts due to the posts of a spammer, wich is deleted now.

You can start a new thread using the "Post New Thread" button, wich can be found in each forum section on the top right of the page.
When you have choosen a title for the thread and finished your posting text, you can add pictures using the Upload File button.
When finished you can press the "Create Thread" button and the new thread will be created.

Bertus