Construction of optical wah

[BN]

This is a spin-off from this thread: "Wah pedal building- how to turn the impossible into possible?" where I asked how to make a shutter in order to build my own optical LED/LDR wah.

This is the reply I got from Paul Perry (Frostwave):

I tisn't difficult, if you can arrange a piece of metal (or, maybe, hard plastic) to move up and down as the pedal moves, then imagine a point that the metal moves past.... now put a LED on one side & a LDR on the other. Now cut a track in the metal so that the LED & LDR see each otehr as the metal moves... now vary to track width to get the right sound.
Actually thns might be easier using transparent plastic & either painting on the plastic with opaque paint, or usign black tape (note you have to stop stray light from the room getting on the LDR). It is fiddly but it is doable, and gives you more freedom over the response than any other method.

But I still have a few questions and ideas I would like to get some feedback on.

I've been thinking of taking a solid piece of aluminium and drilling a hole right through it, then cutting a thin slot in the middle of it. The slot will be orthogonally to the whole. My idea is to put the LED in the hole/"tunnel" on one side of the slot and the LDR on the other side and then let a single piece of sheet metal (or plastic or cardboard or whatever else fits the purpose) slide in the slot and act as the shutter. Do you think this is worth the effort?

My second issue as I recall is that I had connected the LED directly to my powersupply which is a rather crude wall wart. Thus all the 50Hz (I'm European) humming from this got introduced in my wah-sweep. Is it possible to filter the the voltage enough for this purpose or will I need some kind of active regulator (7805)?

It would be a shame not to finish this project after putting so much time in it... 

/BN

[David]

This is a spin-off from this thread: "Wah pedal building- how to turn the impossible into possible?" where I asked how to make a shutter in order to build my own optical LED/LDR wah.

This is the reply I got from Paul Perry (Frostwave):

I tisn't difficult, if you can arrange a piece of metal (or, maybe, hard plastic) to move up and down as the pedal moves, then imagine a point that the metal moves past.... now put a LED on one side & a LDR on the other. Now cut a track in the metal so that the LED & LDR see each otehr as the metal moves... now vary to track width to get the right sound.
Actually thns might be easier using transparent plastic & either painting on the plastic with opaque paint, or usign black tape (note you have to stop stray light from the room getting on the LDR). It is fiddly but it is doable, and gives you more freedom over the response than any other method.

But I still have a few questions and ideas I would like to get some feedback on.

I've been thinking of taking a solid piece of aluminium and drilling a hole right through it, then cutting a thin slot in the middle of it. The slot will be orthogonally to the whole. My idea is to put the LED in the hole/"tunnel" on one side of the slot and the LDR on the other side and then let a single piece of sheet metal (or plastic or cardboard or whatever else fits the purpose) slide in the slot and act as the shutter. Do you think this is worth the effort?

My second issue as I recall is that I had connected the LED directly to my powersupply which is a rather crude wall wart. Thus all the 50Hz (I'm European) humming from this got introduced in my wah-sweep. Is it possible to filter the the voltage enough for this purpose or will I need some kind of active regulator (7805)?

It would be a shame not to finish this project after putting so much time in it... 

/BN

You're working too hard.  Diffraction grating patttern on laser transparency.

[BN]

You're working too hard.  Diffraction grating pattern on laser transparency.

You got it all wrong I'm afraid. I'm not working at all...  My shell has been collecting dust for half a year.

But seriously, you still have to make some construction to let the transparency slide between the LED and LDR and at the same time avoid ambient light. Another problem with the transparency is to get the right taper, at least with my (lack of) photoshop skills. But the theory is working indeed. I have tried out of the wah, the problem as I see it is the implementation. But it may be worth another try as well.

/BN