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Digital Potentiometer - del50003Description.In this Circuit, digital potentiometer, connect pushbutton switches to fast and slow with one end to +7.5V, when you hold the button down the analog voltage will ramp up-down, fast or slow, this will enable you to make a digitally controlled millivolt source or power supply.I did make a millivolt source with this and it still works after 15 years. Some ideas used in this i got from a magazine elektor and some learning i got from another mag Radio Electronics. |
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Theory of Operation.The Fast and Slow push switches each operate a Nand Schmitt oscillator. A flip flop Nand pair detect up or down press and sets counters accordingly. All this work is done by CD4093. Now the counter CD4029 can be up-down and binary-decade and even has preset or jam inputs for thumb-wheel or dip-switch interface.The Cascaded Counters counts the clock you generate by key press to count up-down in binary. The binary digital data is converted to analog by a R-2R resistor network. The opamp is a buffer-non-inverting-amp. The CD4053 Analog switches act like small relays for the R-2R network. they have > 1 tera ohm of OFF resistance and around 100E of ON resistance at +/- 7.5V supply. Data sheets and Information.
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