using serial or parallel port for TTL input

HI,

I would like to be able to use my PC to detect when a transistor is
high. I have found several circuit designs on how to control a
transistor from a serial or parallel port, but none for detecting the
state of transistor.

I want to build a laser beam break detector like this
:http://repairfaq.ece.drexel.edu/sam/laserexp.htm#expbbd

When the beam is broken, a transistor will be triggered and I would
like the computer to sense when the line is high.

Can this be done with a serial or parallel port?

thanks
chad

.

Relevant Pages

  • Re: Analog output from a computers RS232 serial port
    ... > parallel port, you have done your own design in half way, use your own ... > transistor emitter and ground, connect the transistor collector to 5V ... > circuitry, the DC output voltage is from transistor emitter, the base ...
    (sci.electronics)
  • Re: using serial or parallel port for TTL input
    ... I have found several circuit designs on how to control a ... > transistor from a serial or parallel port, ... control external circuitry, as well as using these ports to monitor external ...
    (sci.electronics.design)
  • Re: using serial or parallel port for TTL input
    ... > transistor from a serial or parallel port, ... S0-S2 not accesable) is on pin 15. ... the computer if something goes wrong in your circuit. ...
    (sci.electronics.design)
  • Re: using serial or parallel port for TTL input
    ... > transistor from a serial or parallel port, ... You could alternatively use a control input on the serial port, ... need a larger voltage swing for that (or may not - despite outputting ...
    (sci.electronics.design)
Quantcast