RGB LED Strip - 32 LED/m addressable

[tinyb]

Hi finally back on this project again.
First the problems that have been identified - the first LED doesn't work due to mechanical failure - the strip is coated in a water proof sealant and this has cracked at the end where the connection wires come out, some slight pressure on the led and it works - the control ic isn't affected and passes the data on.

Second - the students did look up the issues with the colour/eye sight/etc, they did discover that green was the first colour restored and the legal colour for all emergancy exit signs but movement (of colour/objects) can also be detected (usually in a grey scale initially) and this is the effect the students were going for - as stated before this project is more about playing with toys than doing anything legal.

finally the code. we have added a simple loop that move the colours down the strip. it looks cool until the we can't suppy enough current to satisfy the current draw. Using a this breadboard adaptor from sparkfun that although the regulator can handle 1.5A there is a PTC which drops out after 250mA (get up to 700mA before issues arise) the whole strip will pull 1.8A if 32 LEDs have the colours on (spec sheet).

[boriz]

On the sparkfun site, a comment by rmeyer says:

"Whew- I don't have the time to do it, but it seems you could mount two of these opposite each other on the shaft of a motor, then spin them to create a supersized full-color circular POV video display."

This is a similar idea to one I had a while ago. Could a dot matrix display be formed using only a spinning strip of lights?

The display perimeter would obviously be circular, and the spinner would have to be perfectly balanced, and the LEDs would have to be flashed at high current with precision timing, and the image would need to have it's pixel co-ordinates converted from rectilinear to polar. But surely it could be done?

A full low-res TV image using a strip of only (say) 32 LEDs.

Anyone care to work out the maths of how fast the processor needs to be?

[hippy]

Anyone care to work out the maths of how fast the processor needs to be?

Let's say it's got to update at 50Hz ( every 20ms ) and you've got to update all spoke positions in that time so ...

20ms = 32 LED's x spokes

then ...

Time per LED = 20ms / ( spokes * 32 )

For 360 spokes ( a pixel line every degree ) that's each LED needs to be updated every 1.74us.

For 36 spokes ( every 10 degrees ) that's 17.4us

I expect the refresh rate can be slower but it's probably still a hard push. There are wheel hub lights which work this way and can show circular images and it's really only a glorified 'propeller clock' so probably worth doing a search and seeing if they offer any better figures to use.

[topkoa]

Just curious if anyone here could provide me with some more detailed information on how you got this to work with the Picaxe 18m2??

I just received mine, and I was tinkering around with submitted code I found earlier in this thread, and what I imagine was the correct wiring (there seems to be no real good information on powering/wiring these things)..

So far I have only been able to get random fast flashes of color, and only on the first 3 LED's.. Basically, I don't entirely understand how to "address" a specific LED on the strip programmatically..

Thanks..

[tinyb]

if you use the code above, it was designed by hippy and modified by me to control the 32 rgb strip with the 18m2. the big problem arrises when you need to provide enough current to the strip to have all 32 LEDS on at once. I used an old computer power supply - the 5V wires (black and red - the yellow is the 12V +ve wire) that can handle upto 2 to 5 amps.

the proble you are having at the moment is what I started out with. basically you are not sending the data quick enough and so the chip is writing to the led with only parts of the data loaded. this give some interesting effects but only on the first few leds.

[topkoa]

Thank you! Its working for me now, I scavenged an old SonicWall power supply from my stash:

Output: 5V DC, 2.4A 12W

That did the trick, the one I was using I guess just didn't have the horsepower at 1.0A...

I uploaded your code and it fired to life! (Now I'm a little blinded, they are bright!)

Thanks again...

[topkoa]

Now I have it running, I am curious if you might elaborate how this code is working?

I'm a little new to the conventions to this programming language, and I think I understand it in some ways.. However, I am puzzled as to how the code works with respect to the execution sequence.

When I "simulate" the code inside the picaxe programming editor, it never seems to exit the "do" loop with the PulsOut statements in it. When I upload the program to the device it seems to cycle through the colors as if it is executing the code in the "UpdateLevels" routine..

I am trying to follow the logic, but like I said its confusing because I cannot determine the proper flow of the code...

Thanks again!

[tinyb]

Now I have it running, I am curious if you might elaborate how this code is working?

That is a good question. the send levels bit i will get back to you on. i understand it but need to formulate an appropriate answer ( the teacher in me)

When I "simulate" the code inside the picaxe programming editor, it never seems to exit the "do" loop with the PulsOut statements in it. When I upload the program to the device it seems to cycle through the colors as if it is executing the code in the "UpdateLevels" routine..

I am trying to follow the logic, but like I said its confusing because I cannot determine the proper flow of the code...

Thanks again!

When simulating, remember that you have memory locations 160 to 255 that have to be writen to the strip ( on the first run only memory space 160 has a value in it of 255, the rest are blank.) by commenting out the gosub send levels, you can see the program change values in the memory locations.( I am using the decimal values here) 160 - red led 1, 161 - green led 1, 162 - blue led 1, 163 - red led 2 ......

when in simulation mode change the memory table from data to ram, scroll down to 160 anjd you should see 255, after awhile the 255 should move to 163 and 255 appear in 161 and the 255 in 163 moves to 166 and the 255 in 161 move to 164 and 255 appears in 163 ( now have a sequence of red on the 3rd led, green on the 2nd led and blue on the 1st led) all the values move up 3 spaces and more values appear between 10 and 162.

this is very poor explaination, if i have a chance i will do a screen record on post it for you.

[topkoa]

Thanks for the explanation, I'm finally getting a few moments to start tinkering with this stuff again..

On a side note, does anyone here have any idea how I might go about powering the led strip in a small portable setup? I'm having a lot of fun with this, however I would like to integrate this into something I can take with me and not have to plug it into a wall socket..

Any ideas?

Thanks again!

[tinyb]

sla (sealed lead acid) batteries could put out enough grunt and be smaller enough - there are many kinds and sizes or lipos could work well. the big issue is finding a regulator that can handle the current draw. my issue when i wanted to use it in a portible situation was the reg i was using would cut out after an amp. didn't take it any further as had access ti a wall socket. you can get 6V SLA so would only need a couple of diodes to drop the voltage to just below 5V. Check the tolerences on the data sheet (i don't have it to hand at the moment.)

thanks
tiny