I have been experimenting with electronic switching and found the sytems very effective , fast and noiseless and a big saving . The total dollars count for all parts is much smaller that the cost of an heavy duty DPDT foot switch . As seen on the previous page suggested electronic switch circuits can be made easily and I have found that their applications is justified .
New mechanical switches on the market like large game switches can be used as a foot switch , they are rugged enought for this application , large and attractive and their cost is very low .
Sequential electronic switch
Developping further the basic electronic switch I have designed a circuit which by using a single push button foot switch will allow switching sequentially up to three effect circuits plus a by-pass .
The Circuit below was designed for my son and after using it said to me " Dad you should patent this as there are none on the market except for those found on expensive computerized multiplexed board " . He was enchanted with its performance , fast , noiseless , no signal loss and easy to use .
ERRATA=Please make correction to the TRIGGER circuit on the schematic and layout .
The .4uF capacitor and the 1K resistor should be connected between the transistor base and ground .
How does it work
As previously mentionned , a normally opened push button switch is used to activate a simple pulse preconditiong circuit made with Q1, 1K ohms resistor and a .4uF capacitor . The output of this circuit trigger is connected to pin 14 of a CMOS 4017 Counter . As the counter is programmed to count from 1 to 4 by connecting pin 10 to pin 15 , each time the switch is depressed , the output of the 4017 , pins 2,3,4 and 7 are switched on sequentially to activate one of the four switches of a CMOS 4066 Analog switch IC . This action is very fast and noiseless . See more about the CMOS4017 applications on pages 34 and 35 then press "BACK" to return to this page .
To identify which switch is activated , an LED is connected to the 4017 outputs with a current limiting resistor , R1-R4 , connected in series , In addition to identify the switches it insure that the switches are off when a positive signal is not applied to the switches gate . These LEDs are labelled in their sequential order from 1 to 4 as shown on the schematic .
The capacitors C1-C4 are shown as optional , but should be used for insurance of good DC by-pass and minum noise . Also as an option the outputs can be tied together as in the case to feed into one input or as seperate ouputs . If you need less than the four switches , tie the unused switches associated pins to ground . and see page 34 for informations on the 4017 maximum count setting .
Suggested layout . PCB is actual size size
Wiring the switch
Install the switch circuit into a sturdy enclosure that will be large enought to accomade a 9 Volts battery , the switch main input and output plugs in addition to three input and output 1/4" receptacles to accomodate three effect circuits as shown . Internal wiring will depend on your choice of distribution whether you will tie the outputs together , if so , use a 10K resistor for each output to isolate the effect circuits, followed by a 2 to 5uF capacitor to the main ouput plug .
To control the ON/OFF power , use a stereo 1/4" plug for the main input for the guitar and wire the voltage source as shown to the switch . As shown the power from the battery can only by switched ON when the guitar plug is inserted into the switch input plug .
By-Pass As shown the by-pass switch is wired internally from the ouput before the capacitor back to output of switch #1 .
LEDs are mounted on top of the enclosure and labelled accordingly such as BY-PASS , WAH , SUSTAIN etc...
Ground loop It is imperative that all plugs grounds be connected together and to the battery negative side to ensure good grounding of the shielded cables to prevent ground loop feed back noise and hum .
For a successful project , please ,
study the wiring layout carefully to determine
the size of the enclosure , types of plugs to use .
Dont' forget the battery and switch size .
I will gladly answer your queries if you get stuck , don't hesitate to send me an e-mail .
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