Milli Volt Source for Printer Port - del20004
This circuit uses a R-2R Ladder Resistor Network to
convert digital data from PC Printer Port to Analog.
This can be used as a Millivolt Source or
Programmable Power Supply.
This circuit is a R-2R, Digital to Analog Converter.
You can replace the R2R with a D-A Chip for better
performance. This circuit is just to
understand the Concept, for learning and
The MFR resistors are 1%, hence the precision of
this Conversion is not very good. It is ok for servo
applications or closed loop conversion along with
the ICL7135. That can be tried with software.
The eight outputs from printer port are latched to
U1 and U2 by controlling U3B using software. Place
data at output then instruct U3B to latch the data.
Then we have a digital byte at output of U1-U2 which
is set by software. This is converted to analog with
Ladder DAC. U4 buffers the Ladder output
and U6 gives a Negative polarity output of same
Source for Printer Port - del20004
view circuit click the Link of PNG or PDF, The PNG
Image can be Drag Scrolled with Mouse.
A 4053 Analog Switch controlled by PC software will
give you a negative or positive output. R41 trimpot
is to calibrate or scale output. If you modify this
circuit, you could output data at a fast rate, then
you have a staircase generator. You can write
software for a waveform generator or function
Source with Digital Potentiometer
You can design a dual tracking power supply over
this. You can loop it with the DVM circuit shown
earlier and make a 12 bit accuracy millivolt or
milliamp source. It will depend more on the software
and little addons to circuit.
The design source is here 20004.zip.
A visual basic 6 program with source, to test this
circuit and experiment is here demo_mvs.zip