I have been trying to learn about controlling my PC's parallel port and have run into a problem.
I am currently trying to control a relay on an adjustable timer and the output from pins 2 -9 trigger my solid state relays no matter what state they are supposed to be in.
When I measure the voltage between the ground pins 18 - 25 and 2 - 9 when they are supposed to be low they are at 3.68 to 3.7 volts (fluctuating) and 4.08 when high.
I can get pin 1 to .075 low, 4.09 high - which works, but I would like to use the data pins.
Could this be a problem with the type of parallel port that my PC has or how it is set up?
The relays that I have are IDEC RSSD with 3 to 32 vdc control at 1 mA. Do I need to or should I use an IC between the port and the relay? I had tried a circuit with a 74LS367 but the one at http://www.southwest.com.au/~jfuller/sio.html seems far better. Is it wrong to wire a relay of this type directly between one of the data pins and the ground pins?
I have what I would consider to be very little knowledge about electronics, programming, and computers in general.
Any help will be appreciated.
Thanks,
Jason