Prop + WS2812B = Bicycle wheel POV?
redheadedrod
Posts: 78
Seeing the WS2812B module posted made me wonder how many of those modules could a Prop control and how fast could they update?
I am looking at potentially trying to duplicate one of the few Bicycle wheel POV kits out there.
Thinking that one could use a string of these modules or maybe a prefabbed string but I am curious if they could be refreshed fast enough with a prop?
If I do like the monkey electric setup I would need 4 strings of 32 (or more) LED's to make the display on each side.
All of the lights I currently have seen use a driver to drive each LED directly where I would like to try using these much simpler serial controlled tri colored LEDs.
If I were to use a prefabbed 144led/m strip I could go somewhere in the neighborhood of 40+ in the same distance as the monkey electric is doing 32. So in all there would be 8 strips to control. Because the light is on both sides there is the potential of only having to light 4 strips but I haven't gotten that far yet since one side would be drawing clockwise and the other counter clockwise.
The units out there have either a preset pattern they do or the more expensive ones you can basically upload a GIF to it and it will play that as if the wheel was a circular display.
Thinking it would be REALLY cool to do and might not be that hard to do if the props are fast enough to handle the updates needed. Also need a way to determine where the wheel is in its spin. I believe Monkey's lights use a gyro and most of the others use a magnet and detector.
I do have other projects I am working on but seeing the new module advertised made me think of this.
Rodney
I am looking at potentially trying to duplicate one of the few Bicycle wheel POV kits out there.
Thinking that one could use a string of these modules or maybe a prefabbed string but I am curious if they could be refreshed fast enough with a prop?
If I do like the monkey electric setup I would need 4 strings of 32 (or more) LED's to make the display on each side.
All of the lights I currently have seen use a driver to drive each LED directly where I would like to try using these much simpler serial controlled tri colored LEDs.
If I were to use a prefabbed 144led/m strip I could go somewhere in the neighborhood of 40+ in the same distance as the monkey electric is doing 32. So in all there would be 8 strips to control. Because the light is on both sides there is the potential of only having to light 4 strips but I haven't gotten that far yet since one side would be drawing clockwise and the other counter clockwise.
The units out there have either a preset pattern they do or the more expensive ones you can basically upload a GIF to it and it will play that as if the wheel was a circular display.
Thinking it would be REALLY cool to do and might not be that hard to do if the props are fast enough to handle the updates needed. Also need a way to determine where the wheel is in its spin. I believe Monkey's lights use a gyro and most of the others use a magnet and detector.
I do have other projects I am working on but seeing the new module advertised made me think of this.
Rodney
Comments
I think it'd be a really fun project to try. However the WS2812B has a "pwm" frequency around 420 Hz which may limit what you can do with it with respect to PoV displays.
Having said that mounting a led strip on a spinning wheel would be a great way to explore what's going on. Who knows, there may be a trick that forces updates inside that normal 420 Hz, or perhaps its possible to work with a reduced color depth but faster updates.
There are also some other variants which have a separate clock line and can update data faster.
If the leds do switch over to a new color on new data it might be possible to have an 8 color PoV, which could still be quite effective
http://www.orbitalrendersphere.com/
Thanks,
Marcus
I haven't explored this. The possiblity of using these LEDs in a POV had crossed my mind but once I read the warning on Adafruit I decided to try other LEDs when/if I get around to a POV display. It's probably when. I have a hard time passing up urges to start new projects.
I can't remember where but someone was using a phototransistor to determine the exact turn-on and turn-off times of the ws2812b's. It'd be a good prop experiment because you could have one cog driving the ws2812b's rapidly, and another cog logging the phototransistor at high speed.
They are SPI driven and can be driven at high speed.
Might have to try picking a string up and see how hard they are to control.
But goes back to the original question. Is the Prop fast enough to handle running a POV like this? I am assuming since you can use them to drive a serial screen at a reasonable frame rate that they will work fine.
And i did see some listed as 144 led/meter and water proof so they would be interesting...
Rodney
I've been able to drive 4 ws2812b strips per cog (80 MHz), or 5 strips at 100 MHz, that stream from hub memory at full speed. The strings can be any length, likewise you can use the whole of hub memory if you like, to drive over 10,000 leds in 24 bit color depth. There are still cogs left over that can be putting the 'image' into hub memory while the ws2812b driving cogs spit data out independently. Its actually a great demo of what the prop can do.
Combined with being able to use a counter to automatically generate the clock for the APA102 or similar, you'll have plenty of time
I just spent a semester programming in MIPS assembly so I am sure that PASM won't be too tough...
I will have to get a string and start playing around with it.
Would be interesting to be able to make a tight circle with one of these and play with it. I am adding projector lights to my vehicle and want to add halos to them and multi colored rings using these and a prop might be cool to play with too...
Rodney
I am considering a simple project with one of my new $9 project boards that uses a 60" RGB water proof string to test this out. I may get the other variation so I am using the same thing.
I am curious how bright these lights are though if at full brightness. I am considering connecting one as a "LOF" (Line of Fire) on my pickup. Thinking an RGB string connected to a propeller will allow me to do some cool stuff other than a simple brake light or running lights. The 96LED/Meter strings are probably good enough. Use it for brake light (red), running lights (dimmer red), turn signals (Yellow), Backup (white), Alarm ("scanner" while armed otherwise can show status of alarm or other stuff..)
Thinking it might be pretty cool to do... And would let me figure out the communication protocol to get ready for a POV...
Rodney