How to make a parallel port monitor

Nowadays, it is less complicated to keep computer equipment in good condition, as more knowledge and equipment is available to keep such equipment working properly. An interesting device to check the operation of the parallel ports of computers is, without a doubt, a monitor that can show with light the good operation of the pins of a parallel port. Next, we will see how to make a parallel port monitor really simple and very functional.

Control8 Software


- One 25-pin DB connector.

- 8 resistors of 470 Ω.

- 8 LEDS.

Assembling our parallel port monitor

We can say that this device is quite simple to assemble and does not require a printed circuit, as the LEDs can even be connected directly to the connector pins, although it is advisable to create a circuit in order to make a much more professional device.

Let's start with the principle of operation of this device, each pin of the connector from 2 to 9 must be soldered in series with a resistor and then with an LED. This circuit can be better visualised in the diagram below:

parallel port monitor diagram

The operation is quite simple, when we connect our device to the parallel port of the PC, we can observe that the output connections that work will light up the LEDS. In this way, we will have the option to repair or exchange the damaged parallel ports of a computer.

We must remember that the parallel ports communicate with the outside of the PC on ports 2 to 9, which is why we check the direct operation of these pins.

parallel port monitor

Another point to bear in mind with this device is that we must use a program, such as Control8, to send communication through the parallel port, and thus, verify its correct operation.

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