Soviet volume pedal and japan sewing machine pedal.

[Death Super Mario]

Many thanks to all. Now it's time to buy and test out.
I post pictures and videos if it works or I have some problems( I think there not going to be any).

[PRR]

> What that LX means.

"Lux".

Back when I was a small boy, there were still candles made of Whale oil.

Before that, for scientific work, there was a carefully specified whale oil candle. The light from it, at one Foot distance, was "one foot-candle".

This wasn't very precise, or convenient. Electronic methods took over.

It does not relate to other basic measurements. The Metric System has been organized so units agree.

The modern unit of light intensity is the Lux.

Typical Lux values:

Living room  ---- 100 Lux
Good workbench -- 1,000 Lux
Direct sunlight - 50,000 Lux

You measure this with a Lux Meter.

You do not have one. But maybe the chart above gives an idea of how many Lux in different situations.

Photo-Resistors are "mostly" used with "dim" light. Dusk-dawn lighting controls. Flame sensors in furnaces. Small lamps. Rarely anything as bright as direct sunlight. So Photo Resistor specifications usually cover the 1 Lux - 1,000 Lux range or a bit more.

> you have to experiment

EXCELLENT advice.

[petemoore]

 These are app notes and suggestions, I found out more after working with LDR's [etc] on some builds.
I preamble by the suggestion: consider and experiment with 'does 'it' matter'' [is there a difference with X scenario, and importantly..if so..which approach is preferrable to your application]...
What will be driving the LDR / do the differences of the LDR compared to the volume pot matter?...
Is compensation or even some EQ effect desirable or not? [might be fun to try out.
Including a direct signal bypass switch makes it easier to find out 'what matters', [and is great for direct vs. effect signal comparisons during experimentation ].
2 LDR in parallel = goes to lower R than one LDR, [or a fixed R in parallel will create a different R curve [reduced max and minimum R].
Because 9V will be right there at the lamp makes an inviting house for an allpass or frequency compensated booster..
Adding or subtracting a cap across the LDR is easy as *solder one end to an LDR lead, touch or clip it across the LDR to try that out.
Note that I have a history of contributing to stompbox building addiction, and have every confidence you'll soon have a cool volume pedal. 

[Death Super Mario]

I got all the electronic parts for the pedal.
I find out that the bestway for testing photoresistors.  I need to make test rig.
I just use clamp cables and 9v battery with resistor and led inside the  volume pedal enclosure.    
First I need to shield the box inside. I think that aluminum tape works. If this helps to protect from breaking parts when they accidentaly connect with metal box.