Continued from yesterday’s article.  Here are the switches I compared.

Mechanical Push Switch (Tactile)

You hear click noises.
[audio:https://gaje.jp/blog/wp-content/uploads/2011/12/tactile.mp3|titles=tactile]

Relay

There are occasional pop noises.
[audio:https://gaje.jp/blog/wp-content/uploads/2011/12/relay.mp3|titles=relay]

Analog Switch

Not bad but click noise intermittently happens.
[audio:https://gaje.jp/blog/wp-content/uploads/2011/12/tactile.mp3|titles=analog_sw_chat_cancel]

JFET Switch

 The most stable so far.
[audio:https://gaje.jp/blog/wp-content/uploads/2011/12/JFET.mp3|titles=JFET]

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My first Optical Organ, described in the following page, has a problem that it makes annoying click noises at key on/off.

https://gaje.jp/projects/synth_effect/optical_organ_e/

I’ve analyzed the issue, and identified that switches to turn sound on/off has the problem.

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Right: charged, left: normal 5V drive

A charge pump is a circuit that boosts DC voltage.  I tried to make a charge pump using Arduino to enhance power supply for a blue LED.  A blue LED typically has higher forward voltage.  Some ones go to 4V, so 5V-supply processors are slightly powerless to drive it.  Thus a charge pump helps to enhance blue LED brightness.

As you can see in the photo above, charged one is brighter.  The supply voltage was increased to 8V in this case.

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