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, Input-Output – del20005

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.

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.

Triac based Lamp Dimmer power control

This is a phase angle control of a Triac which is a evolution from an SCR. The 50 Hz or 60 Hz Sine wave of mains can be turned on at any point after the Zero Crossing.

Design Notes – Power Electronics – 03

Triac based Lamp Dimmer power control

The Voltage ramps up in the sine wave which gives a near “Linear” slope which can be used to trigger the ON at a time delay after zero crossing when the voltage is zero. This is like a PWM but works on low frequency only. Some of the early SMPS(HV for TV and Mains Inverter) by Siemens were built around SCRs. Turning off a SCR is a difficult job for a designer, MOSFETS and IGBT are now used for PWM drive stages.

High Energy Circuits

You can use it with a bulb to vary brightness of bulb, this is a live circuit it can give a shock, enclose in plastic box, the pot should have a plastic knob, use a fuse, you can also use it for temperature control of soldering irons.

The Source file in CadSoft EAGLE format is here

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.

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.

Milli Volt Source for Printer Port

Milli Volt Source for Printer Port

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.

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.

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.

Connection Diagram of AC Control SSR

SSR or Solid State Relay or Electronic Relay Connection Method. This is a Thyristor Based Normally Open 230V Switch that can be turned on / off at a fast rate. This switches at Zero Crossover .Built In Snubber reduces EMI and protects the SSR. USE SAME PHASE FOR I/P & O/P.

AC-AC-SSR Solid State Relay

AC-AC SSR Wiring

  • No moving parts hence no wear and tear.
  • Dissipates Heat when in On Condition.
  • Use adequate Heat Sink or SSR will fail. ( 10g / Amp)
  • Dissipation is 1.5 Watts per Amp thru Load.
  • Input to Output is optically isolated 2kV.
  • This one is AC 230V Control AC 230V N.O. Output.
  • Off state snubber Leakage is around 5 mA.

Notes –

The Termination’s of High Current Lines going to Load must be very tight and crimped. Loose contacts will Spark and cause Fire. Fuse Rating of HRC Fuse – High Rupture Capacity (HRC) Fuse is Safe and Reliable. 5kW Heater at 230V is 5,000 / 230 in Amps of Fuse Rating.