# Goblet Drum Two Channel Sound to Light Circuit

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## Introduction: Goblet Drum Two Channel Sound to Light Circuit

This fun project came about when sound analysing my doumbek goblet drum tonal characteristics.

It became apparent that reliable frequencies could be chosen for the high and low sounds of the drum and filter calculations performed accordingly.

A supply voltage of 18VDC was chosen for the following reasons:

1) Ubiquitous availability of the PP3 battery.

2) The common requirement of 12VDC operation for LED strip lights.

This project is aimed at the competent hobbyist/engineer experimenter. :)

Check out the video for easy 'nuts and bolts' illustration. Enjoy! https://youtu.be/acg4jc02VnI

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## Step 1: Determine Your Goblet Drum Tones

Using a sound analyser (free app for smartphone) determine the tonal frequency of your low and high percussion sounds.

If your drum sound characteristics fall within the scope of the circuit calculated filter values shown, then
no further consideration is required. If your drum characteristics are tuned quite differently you might need recalculate your filter frequencies accordingly. It should be possible to optimise this by adjusting the multi-turn trimmer pots in each filter stage to new calculations using the online filter design tool:

http://sim.okawa-denshi.jp/en/OPtazyuBakeisan.htm

## Step 2: Build the Circuit

Build and test the circuit using a sine wave tone generator and LED brightness (or oscilloscope).

I used a smartphone app to generate the required tones. Direct connection via headphone socket to circuit is preferable.

!! UPDATE !!

I have since found that tuning the low frequency 'doum' filter 5Hz down from the original instruction improves close quarter playing, e.g. if sat on a sofa it's proximity lowers the bass tone of the drum reducing or stopping LED output. New range is now 110Hz to 120Hz instead of 115Hz to 125Hz.

!! UPDATE Sept 2019 !!

Schematic diagram now updated due to component value changes.

More details and a new playing demo on my channel:

## Step 3: Assemble the Circuit Into the Drum

If your build appears to be working (using sweep tone assessments) then fit your project into the goblet drum.

You will need to have suitable fixtures in place for the two channels of LEDs, microphone, circuit board, batteries and on/off switch. I used velcro strips (and pillar standoffs)* for the veroboard assembly / batteries and switch.

For the long LED strip it was necessary to glue it securely. The microphone is glued in place atop a loop of duct tape for suitable mechanical decoupling from the drum body.

*It should also be possible to assemble the veroboard electronics into a low profile ABS box and use velcro strips on the corners, to the inside of the drum. Access to the trimmer pots is required to allow post assembly tweaking for playing styles once the goblet drum is operational again.

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## 2 Discussions

Cool project. Could you share some more details about the assembly process.

Essentially, you have to be familiar with identifying and soldering electronic components onto a copper clad veroboard working solely from the schematic circuit diagram. Your experience will be required to determine the exact layout and connections on the veroboard. This means where to cut tracks, add wire links etc, as well as correct orientation of the components. That will get you the core 'guts' of the project. All parts are your responsibility to order from an electronics supplier, e.g. Mouser Electronics, Farnell components or eBay. Resistors are 0.1% to 1% and capacitors 5% (or less) tolerance of stated value according to the circuit diagram. Cost and availability will be the determining factor.

Tools you will need: Cutters, soldering iron, solder, sucker/solder braid, trimmer tool for pots, DMM for resistance and voltage checking, tone generator (smartphone app will do).

The LED strip will need to be glued just below the drum head and allowed to set (use tape or gentle clamps) to hold in place. If you're lucky the backed adhesive might work (it failed miserably with my 'Phobya' LED strip shown in the video).

The Red LED cluster is really up to you. I bodged (after some dremel reaming) 4 high brightness 5mm LEDs into a fresnel lens cap. You could go hard with a 1W SMD type LED or similar and work with that instead. On my cluster I used the (now epoxy covered) LED legs to wrap the pipe cleaner around to suspend it in the middle of the drum.

There's not much else can add here, unless your more specific maybe. Hope this helped, Atb.