View Full Version : COM Port Issue Controlling Olson 595

12-01-2012, 10:46 AM
Hi everyone,

I'm having an issue I can't figure out. Some background. I've used an old desktop in the past to control an Olson 595 controller with the parallel port. No issues. This year the desktop crashed (bad mother board) so now I am trying to use an older laptop I have. The laptop does not have a parallel port but the docking station that it sits in does. When I hook everything up nothing happens. I connected a scope to the clock and data lines on the parallel port while the Olson 595 was connected. Signals are making their way out the port, however, they are significantly rounded and barely hitting 5V. I think the signal are not being recongnized. I assume it is that the docking station I have does not have as much driving capability as the desktop I used to use.

Any thoughts on how to get it going?


12-01-2012, 11:35 AM
I would use a cmos buffer chip that has a schmitt trigger, like CD74HC14. To keep the cmos in its center of the hysteresis curve, I would capacitive couple it from the LPT port.
This may or may not be necessary. Since this chip is an inverter to keep the same polarity you want it feed to another gate input, using two gates for every LPT port input. This chip has 6 gates so you have 3 ports that can be converted.

12-01-2012, 11:43 AM
I thought of that too. Was hoping not to have to put together a circuit.

12-01-2012, 11:56 AM
Since your current configuration doesn't work, something will need to be tried.
Another simple check is to use .1uf ceramic capacitors to AC coupling the port signal to the 595 input. Don't know if a resistor or two is required to center the dc point on the 595 inputs.
I suppose this is still "circuitry" and may not be your solution.

12-01-2012, 12:17 PM
A simpler solution might be to use a Ren-C and the serial port, bypassing most of the problems of finding a parallel hardware port compatible with the 595. Adding the Ren-C allows the same controll that you have now, but adds the option of dimming as well as greater distance between the computer and the controller because RS232 or RS485 can be used.

Just a thought...