Parino philosophy.

Picture of the Parino card The Parino I/O card is a real Input/Output card. There are more I/O cards for the LPT port of a PC, but in most cases there is a more or less bigger drawback.
Conrad as an example has an I/O card which has no I-function. 8 Relays and no inputs. This convicts you to timer functions as your only "feedback" mechanism. You can switch a motor on, but you have no way whatsoever if the motor driven part has reached its target position or not. So the only possible control you have is to make sure the targetposition is supported by a big bolt and you let the motor spin until it must have reached the end-point. This automatically means a lot of noise from the motor before it's turned off..
Inputs are essential when you want to control. For this reason I did not go for compromises when designing the Parino card.

The LPT port normally has 12 lines that can be controlled by the attached computer (the outputs) and 5 lines which can be read by the computer (the inputs).

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PCB population options

Since I have this habit of not wasting things, even when it is related to individual bits (yes, Cartoonsmurf, he who does not cherish the small, is not worth the big [dutch proverb]) I used every bit that is present in the complete LPT interface. This resulted in the following schematic:

Parino circuit description.

Please click on the picture to get a more detailed view! The schematic is a downsized PNG file. If you click on the picture, a new window opens and you get a picture with more details.

What it comes down to is:


Explanation of the circuit.

Even if there is not an infinite amount of detail in the drawing, still the overall structure will be clear:

Analog
outputs		 The signals of the printerport which can be written to first enter a buffer (there are 7 in a ULN 2003A) after which a relay coil is energized.
The relay pulls two contacts together and an electrical connection is made between two poles of a PCB connector.
Digital
outputs		 After I connected the relays 11 and 12 (B and C respectively) I ended up with two unused ULN 2003A gates. You know it: wasting is a shame, so we had to find an application for them. So I put an opto coupler on each buffergate. This gave the Parino card two lines of digital output.
Analog lines, like relays, can do 25 Hz, if you're lucky, while wearing out rapidly.
Digital lines like this can easily do 250 kHz.
Current
sources		 The inputs needed to be foolproof. So, no matter what DC voltage was applied to the inputs, the current through the opto coupler LED must be the same.
This called for decisive actions. With just a resistor you won't be able to get it done. So we needed to have a current source. The easiest current source is a TL 317C with a resistor between V-out and V-adj. See the schematic for details.
This way, the user can take whatever voltage between 3 and 40 Volts DC to force the opto coupler to change state. The current source will make sure the opto coupler is not overloaded.
Power
supply		 The Parino card needs it's own power supply. The Schrack RE 030012 relays have a 12 VDC coil at 720 Ohms. That's about 17 mA per relay. Too much for a 9V battery. So we needed a separate power source. The power supply is integrated on the Parino card with a rectifier, filter capacitor and a 7805 regulator.
This 7805 may be too powerful since the +5 Volt is rarely loaded by more than 40 mA, but the 7805 is cheaper than the 78L05 and the T)-220 case of the 7805 can dump more heat so it runs much cooler and the regulator will last forever.
The presence of a rectifier enables you to run the Parinocard from either a DC (12 to 15 V) or an AC (7.5 to 9 V) voltage. And it doen't matter how you connect a battery to these terminals.
Opto
couplers		 The PC 817 opto couplers that I used on the Parino card are small and cheap chips with a high reliability. They come in a 4 pins case, so (in the rare case that one breaks down) you can exchange one individual coupler without having to automatically replace the other two (undamaged) chips.
With a PC 837 this would be impossible since it contains 3 opto couplers and if one breaks down, the two good ones must be replaced as well. And that's a waste!
Relays The relays are compact and relatively cheap relays. Conrad always stock them under number 50 48 66.
Schrack is an Austrian brand that was taken over by Siemens a few years ago.
We use the Schrack RE 030012 type of relays here.
PCB
terminal
blocks		 The PCB terminal blocks are industrial grade connectors. The power supply is connected to a separate 2 pole terminal block.
The in- and outputs are located on separate 6- and 8-pole terminal blocks. These very long terminal blocks are especially convenient because they are rigid and all 6 or 8 pins are soldered to the PCB. This makes operation of the connectors safe and there is only a very small chance on damages due to forceful tightening of the screws.

On all fronts, quality was the bottom line. All parts are OTS (Off The Shelf) commodities. These have been around for years on end and will be so for decades to come. Eveything has been overdimensioned. This makes that time will have only a small impact on circuit performance.

The above schematic was made with the PADS kit. The file PARINO42.SCH is also available from this site. So, if you take some time to get PADS and download the schematic via the DOWNLOAD option in the navigator, you can work with the original drawings. This will also enable you to make perfect prints on your own printer. Printed schematics are 20 to 100 times better than scanned GIF files.

Layout of the built-up PCB.

After I composed the schematic, I exported it to a socalled netlist. This netlist was then imported by the PADS PCB router. The PCB layout is available in the file Parino42.job. Below you will find a shrunk picture of the topside of the PCB, just to give an impression of what it looks like.

Click on the picture to enlarge!
The picture you see above is a downscaled image. Please click on it to get a more detailed view.

Parts kits or ready made (and tested).

I still stock a lot of parts for the Parino system. I guess I still have some 70 odd empty PCB's lying around. If you want to construct a card yourself, a professional quality PCB is a good startingpoint. Furthermore I have varying supplies of the following materials:

For many parts it is advisable to first visit Reichelt in Germany. First grade equipment for modest prices.

Bill of materials

Here is the BOM (Bill Of Materials) for the 'Parino 4' device. The table speaks for itself.

Part Description Amount Price Total
PCB Printed Circuit board 1 4.00 4.00
Sockets IC socket, 16 pin, 300 mils wide 2 0.05 0.10
IC socket, 8 pin, 300 mils wide 2 0.05 0.10
IC socket, 6 pin, 300 mils wide 2 0.05 0.10
ULN 2003A Sevenfold high current open collector buffer 2 0.20 0.40
Centronics 36 pin Centronics connector, female 1 1.20 1.20
Relay Relay, Schrack RE0030012, SPST 12 2.00 24.00
7805 Voltage regulator, fixed, 5 Volt, 1 Ampere, PowerWatt 1 0.20 0.20
Rectifier Round rectifier, 1500 mA, 80 Volts 1 0.20 0.20
Capacitor Capacitor 100 nF 1 0.15 0.15
Capacitor 22 nF 5 0.10 0.50
Electrolytical capacitor 470 uF, 25 Volt 1 0.20 0.20
PC 817 Opto coupler, Sharp PC817, 4 pin DIP package 7 0.44 3.00
Resistor Resistors, metalfilm, 1/4 Watt, 2 x 180 Ohm, 5 x 120 Ohm, 5 x 4700 Ohm 12 0.08 1.00
LM 317LP Low power LM 317 LP, TO92 package, connected as current source 5 0.20 1.00
Jumpers Jumpers and shorting blocks for [en/dis]abling relays B and C 2 0.12 0.25
Terminals 2 pin terminal block, PCB mount, pitch 200 mil 1 0.15 0.15
6 pin terminal block, PCB mount, pitch 200 mil 1 0.40 0.40
8 pin terminal block, PCB mount, pitch 200 mil 4 0.60 2.40
Hardware Screw (M2.5 x 10), nut M2.5, washer M3 2 0.10 0.20
Total for parts 39.55
Profit Engineering charges 1 35.00 35.00
Grand total 75.00

Bottomline: if you feel I am underrating the engineering charges, please feel free to add an amount that gives you a better feeling.

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Page created June 2003,

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