Digital Potentiometer - del50003
Variable Parameters like voltage, current can be
obtained by using a Digital Potentiometer.
Microcontrollers or Counters operate FET CMOS Analog
Switches. The switches configure resistor networks
to adjust circuit performance. It could be a Speed
Control of a Motor or Brightness of a Lamp. Volume
controls and Tuners also can use this.
Trimpots and Presets
Description. - 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
Digital Potentiometers - Maxim
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.
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.
MilliVolt Source Prototype made in the 80s
Here is a Millivolt Source i built for Calibration
in the early days. It uses only CMOS Digital and
Mixed Chips from Intersil and CD40xx Series. 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.
Later i tried a unit with 8748 part of the code in
my uC section. This is with Ramp-up and Ramp-down
using only two buttons. This works even now, The
support below is an HRC Fuse Holder made of Phenolic
or Epoxy Resin. The mV Terminations are on Top.
MCS-48 Examples and code
This was supposed to have Analog in and Analog out.
Some parts of the circuit may be in the 80C51 page.
This has ramp-up and ramp-down settings for the
Increment and Decrement buttons. This helps setting
setpoint quickly. There is also debouncing for the
Data sheets and Information.