# 16 Step Sequencer Quantized Vari-Clock Module

Posted on Feb 5, 2014

A mechanism by which a normal pot could be used as a digitized pot since I need each pot`s setting to be converted to a number between 0 and 15. I use that information to determine the duration for each step. I accomplished this by designing an analog to digital convertor that could take a pot`s position and convert it to a number between 0 and 15 relatively quickly (within 300 microseconds or so).

The A to D convertor is the type that uses a D to A convertor to create a stepped ramp voltage to which the input is compared. When the stepped voltage output of the D to A convertor is a few millivolts above the current input level the current count from the D to A convertor is clocked into a latch. The latched output is the D (digital code) in this A to D convertor. The circuitry is described below. The A to D convertor is realized by U1, U2, U3 and U4. U2 is a CD40193 binary counter whose outputs are connected to the classic R/2R network (made up of R6, R7, R12, R16, R15, R18, R19, R20 and R22) which converts the binary output to a voltage level which is linearly related to the binary count (I refer to this as the D to A element of the A to D convertor). R23 (470K to +12V) causes the output of the R/2R ladder to be positively biased a bit. This is to allow sensing of zero volts by the A to D convertor. The counter is clocked by U1-A, C17 and R26 which are wired as a simple phase shift oscillator. The CD40193 is wired to count upward and thus the output of the R/2R ladder (D to A) is a positive going stepped ramp wave whose voltage levels correspond with the binary output of the counter. U3-A buffers the R/2R network output and applies it to the non-inverting input of U3-B via 10K resistor R17. U3-B`s inverting input is connected to the level shifted input voltage (Point DV). Point DV connects to the common I/O point on...

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