Re: [CAD_CAM_EDM_DRO] Parallel port power increase

m0nkey0ne wrote:

>Hi all, I have to start a new chain here on my project. I have my
>M57-102 Compumotor and Driver connected to port 2 through 5 on my
>parallel port on my laptop. I have a .dll file in my systems folder
>and call it from a program I am building on VB6. The motor is
>receiving a signal because it moves slighty as instructed, however
>the port is not going high, only to about 1.5 volts. Is there a
>schematic for using MOSFETs or iso-optical transistors, (I only have
>a vague idea of what the heck I'm talking about), that will send
>higher voltage from a higher powered source? I expect to use a 5 V DC
>power source so shouldn't need the circuitry to control that.
>
>

Optical isolation is a good thing, so here's a circuit.

Use a Fairchild H11A817D (available from Digi-Key for $0.56 each)
for each bit. It has a guaranteed current transfer ratio of 300%, meaning
it triples the input current. Connect pin 1 to +5 from some source, such
as pin 1 of the game port, or a hard drive connector. Connect pin 2 to
a 120 Ohm resistor, and the other end of the resistor to the parallel port
pin of interest. This will cause the LED to light when the parallel port
goes to a low (0 volt) level. Now, get a separate source of +5 V (a
wall-wart
supply will work, or maybe there is a 5 V output on the Compumotor
drive.) If I recall, the Compumotor drive had plus and minus inputs
for step and direction. Connect the + input to the external + 5 V supply.
Connect the - input to pin 4 of the optocoupler. Connect pin 3 of
the opto to the - of the external power supply. This should deliver
sufficient current to the driver.

Jon