Friday, December 28, 2018

Test Circuit for Logic Analyzer software

This is a Test Circuit for Logic Analyzer software, with the Simple port circuit. The VB Logic Analyzer works, but is just an example program to test and learn.

Test Circuit for Logic Analyzer software
The speed at which the logic state changes say like 10 M Hz while probing even a PIC or 89C51, is too fast for this circuit. For that, the incoming data has to be spooled or stored in RAM at real time, by the external Hardware itself.

Test Circuit for Logic Analyzer software - del20006

As this is a Parallel Port Interface, an Embedded High Speed Digital RAM Storage of Multiple Logic input Channels with Signal Conditioning in the front end, could do the job. This is the minimum, if you want to program the rest of the instrument on Computer Software.

Thursday, December 27, 2018

Simple Printer Port Interface

Printer Port Circuit to see the inputs logic state and drive a few outputs. The preset control program helps test out the circuit operation. Use safe 5V Levels.

Simple Printer Port Interface
So i made some example circuits and VB programs for students. A demo Milli Volt source, Digital Voltmeter and Logic Analyzer examples for learning, are on these pages. I have tried to derive power from PC itself in this circuit, Care should be taken not to short circuit or apply any voltages above 5V to PC Port Pins

There are protection in all chips these days, but you may stress the limits, so design and use opto couplers to be on the safer side.

Simple Printer Port Interface

74HCT373 is the only chip used to interface the real world with the PC Parallel port. The Inputs to this chip are protected with Resistors and Zeners. 3 outputs of PC are also monitored using LEDs. This gives you a IO interface for experimenting. Below is a Preset counter simulation that you can use with this circuit for testing. Schmitt Triggers and Signal Conditioning may be required for Noisy and Non-Sandard Inputs.

Wednesday, December 26, 2018

Milli Volt Source for Printer Port

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.

Milli Volt Source for Printer Port
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.

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.

Milli Volt Source for Printer Port - del20004

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.

Hobby DIY Electronics