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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 Experimenting.

Millivolt Milliamp Source

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 a R-2R Resistor Ladder DAC.  U4 buffers the Ladder output and U6 gives a Negative polarity output of same analog value.

millivolt or milliamp
                        source

PNG-Schematic     PDF-Circuit     DSN-Source
Milli Volt Source for Printer Port - del20004
To 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 generator too.

Millivolt 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