Creating an optical tremolo effect

I think I can make something similar to this DIY light-controlled tremolo:

Or the updated version of the same idea:

My main question is, can anyone make a recommendation between using the fan or the DC motor to move the disc? Is the fan faster than the DC motor? Would one of them spin up to speed faster than the other? Which one would be easiest to mount the other necessary pieces on? Which one would be more reliable?

At this point I’m thinking of doing a pretty bare bones version of the original idea. Here are the other bits I was thinking I’d need:

microphone (in input mode) or a series of other sound generating bits
light sensor
dimmer (to control fan/motor speed)

I could use an external light source or maybe one of the various LED bits, but I’m not sure which one. Any recommendations?

Is there anything else I might be forgetting?


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Hi @Schwa_Iska,
Nice idea to build a tremolo system!
I think it can easier be made with Littlebits than with the parts shown in your links…
The main difference between the motor and the fan is the RPM (rounds per minute) value.
The motor needs nearly 2 seconds for just one cycle and the fan is much much much faster.
For the motor however there is the motormate for attaching things on the shaft. On the fan you will need double adhesive tape I think.
Indeed the microphone bit can be used as input, also for an electric guitar. (would be nice to use this tremolo with a guitar)… :guitar:
I made a project last year with a three string dulcimer, connected to the microphone bit with three home-made pickup coils under the strings, made from old 24 volt little relay parts combined with little magnets.
You can take a look here:

Hi @Schwa_Iska :slight_smile: Whatever route you choose, please keep us updated on your progress. It sounds REALLY fun.

Here are a project that might interest you: by @Ginger

and I know some Bitsters were using an IR led pointed towards a light sensor separated by a paper plate spinning on a DC motor. @ed_littleBits do you have a video or picture of this you could share?

Hello @Schwa_Iska and @JackANDJude
I experimented a bit here with a self made optocoupler circuit ( see also the MiniPops project : and replaced the bright LED with a RGB LED.
With the Brute LFO ( free app for IOS ), you can creae a tremolo effect.
Just connect the IOS device to a microphone bit ( i21 ) and connect this to the RGB LED bit ( o3 ).
Place the RGB LED on top of the Light sensor bit ( i13 ).
Now, experiment a bit with the settings of these bits to optimise.
Now, cover this assembly with a cardboard cover.
Place this Light sensor bit between your synthkit chain and you’re ready to tremolo away.

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The cardboard cover on your assembly is adorable @frankje :slight_smile: I detect an opportunity for a 3D printed accessory. Is size the primary factor in preferring an RGB led over the bright led?

Hi @JackANDJude !

Yes indeed, the 2 bits stick easily together because of the magnets inside.
Just reverse the top bit so that opposite magnets attract.
The cardboard is in fact a light shield and holds the 2 bits together.
The RGB Led is a better choice for the slower rise and fall of the light. The Bright Led is too harsh.

So many great ideas!

Thanks for the info. It sounds like the fan will be much more effective for my purposes. I’m excited to try it out on guitar… wait did you mean on a guitar? Oh, just imagine the windmills, the fans… and the mechanically controlled temolo too!

I really like all the thought that went into bits on a string too. So many different ways to play the same three strings.

Thanks for the encouragement and the inspiration. I’ll keep posting. :smiley:

:open_mouth: That’s really cool. I’m gonna have to try that.

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Hello @Schwa_Iska
Unfortunately, the fan can never create a sine wave, needed to feed the tremolo. With the Brute LFO, there are plenty of sine waves that can interact which each other (if needed )to create cool effects. I’ve tried it yesterday with the optocoupler bit and it works like a charm.
I’ve tried different LED bits, but the RGB bit works best and it fits the Light sensor bit too :stuck_out_tongue_winking_eye:
Of course, you always use the fan with a bright LED and pulse oscillator to create a stroboscope effect :sunglasses:

By the way, have you some ideas to create vibrato on the oscillator bit ?