Optical hihat controller

[Antagonist]

Not my intention to revive this thread, hope someone can help me, I've been trying to make this work for the last 5 days and I'm out of ideas, I measured the voltage and it changes from 0.02v closed to 2.81v open (ring/tip)(ground/diode cathode). 3.30v (ring/sleeve) all the time, I opened my megadrum and double checked for shorts in the input, and also the connections are ring = ground, sleeve = pin40 = hi-hat power, tip = pin39 = low impedance pedal. Only thing I didn't try is using the high impedance input and measuring pin13 of the first MUXer like dimitri suggested on page 12, since I don't know which IC that would be(It was built by dimitri and not me ).

I tried connecting a pot with the tip connected to the middle of the pot to see if I could get a response, and nothing happened(tried all hi-hat settings like pot, f.controller). Upgraded the firmware today and tried again with same results.

Is there any way I can diagnose what is going on? does anybody know which one is the MUXer? multiplexer? by the way the photo-resistor is IR, but I'm surprised that the pot doesn't work, maybe I'm doing something wrong? if I can get the pot working I'm sure the pedal will work, just need to figure out why it doesn't respond.

I apologize for my lack of knowledge . Any help is appreciated, thank you.

[dmitri]

1. You should have contacted me directly if you suspected a fault in the module rather than opening it up. You don't have to do anything inside the module.
2. Sleeve is ground and ring is power.

[Antagonist]

1. You should have contacted me directly if you suspected a fault in the module rather than opening it up. You don't have to do anything inside the module.
2. Sleeve is ground and ring is power.

I didn't think it was a fault in the module(since it was built by you), most likely me doing something wrong, I only opened the enclosure and checked the contacts that I soldered myself, I didn't touch the rest.
2 That did it, sorry confused the terms, opened it, re soldered to a new input and it works perfectly now , thank you for the help, I feel like an idiot

[privatex]

Well someone is patented this idea couple years ago. I found this patent document:

http://www.faqs.org/patents/app/20120048099

[dmitri]

I believe if there is a prior work than the patent is not valid.

[privatex]

Indeed, racer52 was testing this approach 2009, Admir even earlier so it must be scam in try.

[midnightlamp]

This is the schematic:

opto.png

So this is a bump to a very old thread, but I figure it would be helpful for any Megadrum owners in North America who want to build an optical controller easily.

Using this schematic I found the following components worked well and are readily available:
LED = White 5mm 5500mcd@20ma, 20degree angle 3.4V. Example part from Digikey: https://www.digikey.ca/en/products/deta ... 30/7604628
Phototransistor = Vishay TEPT5700, 570nm peak wavelength, 100deg viewing angle, 6V max EC voltage, 20ma max collector current. Example from digikey: https://www.digikey.com/en/products/det ... 00/1681193 . Another part that was tried: Excelitas VTT9814FH and VTT9812FH, all worked fine.

I did have to play around with R1 to get the right current across the LED, and found that 100ohms worked for me. Likewise I had to adjust R2 a bit - I ended up using 5.6k in the end, but tried from 3.3k to 10k.

This works with a spacing of approximately 4mm between the LED and the photodiode, with the impedance switch "up" (low) on the megadrum module, I get a reading between 350-550 (closed to open).

Attached is a picture of my DIY controller in a printed housing: Note this sits under a set of Jobeky hihats and lets you use a standard hihat stand, and a drop clutch (because the pedal follows the hihat motion itself).

[milindneta5]

A common hihat pedal goes from open to close, and that range in terms of phisical cymbal movements is usually 2 cm. How can you make it gradual with a standard acoustic hihat stand?

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[midnightlamp]

The little printed setup I have above is very similar to the design shown in the rest of this thread - using a tapered gate that closes the light transmission between the LED and the phototransistor.

This one is set up more for a traditional drummer - where the motion is actually tiny and is quite sensitive and requires a bit of skill to control. For me personally I use closed sounds, slightly open sounds (sloshy hats), open sounds and quick transitions from open to closed, so using the controller in this form is usually a compromise.

How I adjust it is to have the lower hat sit on the protrusion at the top, and I have a machined spacer that sits between the plunger (the portion that closes the optical circuit) and the top hihat. I adjust this with small shim washers until I find the feel is right! To me this feels a lot more natural than most pedals on e-kits.

In my personal view, if one wanted more range/control you would need to place this on the pedal itself - but I don't think that's needed for me.