This IR Responder volume control unit transmits a pulsed infrared beam that is bounced off your hand and then picked up by the IR Receiver. Using a pulsed beam minimizes the problem one might encounter in different levels of room lighting. The circuit board I made takes this detected IR signal and converts it into controlled white LED light which controls a LDR that is governing how much sound passes through to the main amplifier. My LED and LDR combo are a homemade LDR Opto-coupler which has become difficult to find on today's market.

Raw Sample.mp3 or Bit of Reverb

VELLEMAN Transmitter - Schematics - Receiver

Where to Buy for $7.18 plus shipping.

Note: You might buy an extra kit for backup. The foil side of the board cracks loose and damages easily!

Volume Board PDF (127k) You etch this board.

Currently no schematic is available for this board, 
study the layout. The board uses 9 volts. Connections are made to the Comp connection and the Audio In & Audio Out.

Use a Vactrol  VTL5C1

Note: The VELLEMAN IR sensor and two IR LED's could be mounted on a cable away from the main pc board so they could be placed in something more artistic. The main electronics could then be in a remote location.

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Misc IR Volume Control Lab Notes Below:

The VELLEMAN IR boards are extremely fragile, do not move any components after they are soldered in place or "you will" rip the the copper foil pads from the pc board adhesive and tear it loose from its copper trace. The copper foil is paper thin.

Power Supply:  
The IR boards must have 9 volts +/- .4v or else they "will not" work. Use a low current adapter 200 or 300 ma. Here is a good 9 Volt AC/DC Adapter Regulated & Filtered  273-314 16.99  View at Radio Shack   Wired up properly this one adapter can power all of the RS Illusion boards and volume control.

The RS Illusion Theremin uses about 10 ma while the pulsed IR Volume control section uses about 100 ma.

You can plug the power adapter into the IR receiver board at SK2 and from SK3 run power to the IR transmitter board, the homemade IR responder board and through the Audio cable power the RS Illusion M3 board which powers the L2 oscillator board. The RS Illusion should receive proper grounding through the audio amp connection. The audio amp must have a "three" prong power plug so earth ground is available.

View the VELLEMAN IR Receiver schematic for better understanding.

When using the power jack on the VELLEMAN IR Receiver board with the AC/DC power adapter then you will need to put a jumper wire across the jack terminals on the pc board which break contact when the power plug is inserted into the jack. You want the SK3 contacts to remain active along with the SK2 jack contacts.

Do not move or twist the IR Transmitter or receiver LED's after they have been soldered in place, you will damage the foil side. Angle the board mounting for proper IR LED alignment.

To avoid damage to the underside foil mount the VELLEMAN IR Receiver boards red indicator LED closer to the board to avoid accidental foil cracking due to bumping.

IR Responder board:
Use night light "LDR" along with its white "LED".

Bend LDR with needle nose tip spacing, LED is a full bend.

Glue with epoxy the LED tip to the LDR then paint "black" leaving the back side of the LED clear so you can see it turning on and off. Blacken this area later after everything is working. 

The flat side of the white LED is the negative side. Observe this after gluing the LED to the LDR.

Adjusting IR Responder board:
The first test is to reflect the infrared beam from VELLEMAN Transmitter board back to the VELLEMAN Receiver board which should turn off the indicator red LED on the Receiver board. Start with the adjustment of Pot 1 on the RS Theremin IR Responder board fully counter-clockwise, the LED should be on. Begin turning the Pot 1 adjustment screw clockwise until the LED just fully extinguishes. The bright white LED against the LDR should now turn off as it senses reflection from the VELLEMAN Receiver board.

Required Modifications:

Modify the VELLEMAN IR Transmitter board by placing 100 ohm resistor in series on the positive side of the power connection to the  board. Also add a 47 uf capacitor across the positive and negative side after the 100 ohm resistor for more filtering. This modification will reduce the 5khz pulse modulation noise generated by the transmitter board along with improving the proximity response of your hand control of the audio. These two parts can be adapted onto the transmitter board. Schematic of this modification coming soon.

When using the power jack on the VELLEMAN IR Receiver the jack normally close contacts break open when a plug is inserted. Avoid this by adding a jumper wire on the foil side of the pc board. You want the jack power to continue to be supplied to the battery power connections for feeding the Transmitter board and the IR Responder.

Place a .1 uf capacitor across the Audio "Input" side terminal of the RS Theremin IR Responder to reduce the IR PWM background noise from passing through the sound.

The stereo cable between the IR Responder and RS Illusion can carry power from one common power source.