Slow Dance ( Time Frame ) using Espruino ( any flavor ? )

[espruino-discuss2]

Posted at 2017-02-18 by stephaneAG

Hi there :)

I was asked to recreate the idea demonstrated in these awesome setups:

https://www.kickstarter.com/projects/xercyn/slow-dance-a-frame-that-slows-down-time
http://www.instructables.com/id/Slow-Dance-a-Fusion-of-Art-and-Magic/?ALLSTEPS
http://www.instructables.com/id/TimeFrame-a-Time-Portal-to-Put-on-Your-Desk/?ALLSTEPS

-> of course, Kudos to the respective original author ;)

Now, after a quick read of the schematic involved:
https://raw.githubusercontent.com/cubic-print/timeframe/master/electronics/PCB_schematic_V3.JPG
I could start a new version :)
https://circuits.io/circuits/4045924-slow-dance-time-frame

Now, all that is good, but looking at the code ( whatever the version .. https://github.com/cubic-print/timeframe/tree/master/software) , it seems to be using some register's mambo-jambo tricks specific to the AT328P for precise timing purposes ( .. )

I was wondering if I could achieve driving LED stripes in a "stroby manner" while simultaneously driving correctly the electromagnet using only js ( actual DACs or using PWM .. ) or if I had to look into writing a quick module that'd allow me to do so :)

Long story short, the objects getting vibrations from the electromagnet have to oscillate at 80Hz while the LED stripes have to strobe at 79.5Hz to get a "beat freq" of 0.5hz, perceived by our eyes as a very slow motion ( etc .. ;p )

For the fun of it, if anyone has hints/advices on the above, remember the "water + subwoofer + camera ( filming at 24 fps ) + audio waveform" trick ?
By modulating the waveform from 23Hz to 25Hz, the water appeared to go backward or forward and also gives a really nice effect ..
.. so another question may be how to replace the camera fps' by strobe lights while having those oscillating at a freq enough for our eyes to perceive the motion ? ..

Looking forward to reading some answer on this,
Happy coding !+

[gfwilliams]

Posted at 2017-02-18 by @gfwilliams

At 80Hz you could easily use Waveform and analogWrite (with forceSoft:true) - they use the same timebase so will always be properly in sync. You can output a sine wave from a table using Waveform and can then use analogWrite to output the strobe.

With the camera - I think the problem you have is that most video cameras don't use a global shutter (it's a curtain shutter) - so you're going to see 'banding' if you use a strobe light.

[espruino-discuss2]

Posted at 2017-02-19 by stephaneAG

Thanks for the inputs :)

I'll order some of the stuff I'm missing to test a build tomorrow, but in the meanwhile I did my best to translate the original code to js
https://github.com/stephaneAG/Espruino_tests/blob/master/SlowDanceTimeFrame/SlowDanceTimeFrame_Espruino_wip.js

Concerning the strobe light & the electromagnet, since the original code doesn't use any waveform, I bet I can rely only on using the following, although I'm not sure how I'd use - if necessary - the 'magDuty' & 'ledDuty' vars ( 'magTime' & 'ledTime' shouldn't be needed since the freq is set thanks to analogWrite's 3rd param )

analogWrite(magPin, 1, {freq:magFrequency}); // L98
analogWrite(lightPin, 1, {freq:ledFrequency}); // L100

Concerning the "water trick", I'm sure I didn't explain it well, so here it is:
https://www.youtube.com/watch?v=mODqQvlrgIQ and also https://www.youtube.com/watch?v=uENITui5_jU
My goal 'd be to replace the camera by strobing lights ( keeping the effect we see through the camera thanks to the strobes )

I'll post updates as they come ;)
+

[gfwilliams]

Posted at 2017-02-20 by @gfwilliams

Ahh - got it. Yes, just two analogWrites should do it fine :)

[espruino-discuss2]

Posted at 2017-02-22 by stephaneAG

;)
( 'just checked my DHL status: hardware's coming home :D )

I'll post tests as soon as I receive & build the stuff ;)