[WriteLog] Parallel Interface

[Kevin Stover]

Thanks to George and Jim for their input.
I'm thinking I'll just fix up the parallel port interface but install a 
second LPT in the machine.
The cards are cheap and easy to setup. If something goes terribly wrong 
I've still got a printer port.
Really looking forward to contest season this year from the "black hole". 
HI HI!

Thanks again.
Kevin, NØRKX




At 05:47 PM 7/6/01 -0400, you wrote:
>Kevin,
>You could use the Comm port CW line and the 4N33 CW circuit to drive your
>level translator.
>
>But the LPT port is a TTL output (5 VDC and Gnd) and does not have
>sufficient "drive" current to drive the LED in the 4N33.  The LPT port can
>"sink" enough current but that current must be supplied by another 5 VDC
>power supply with its own return line connected to the LPT computer Gnd
>line.  I have tried to drive the LED from the LPT port here and it is both
>risky and unreliable.  It is risky in that you may burn out the LPT drivers.
>It is unreliable because when you limit the drive current you get may or may
>not provide sufficient current to adequately switch the 4N33 output stage
>and key your circuit.
>
>I have thought of trying to steal the additional 5 VDC from the computer
>itself but have not tried it yet.  I just use the 2N2222 circuit directly
>and have not had any ground loop problems in that circuit in several years
>of contesting.  It will drive your level shifter nicely.  I have used that
>circuit here also...  (with a TS 530)
>
>George .. W1ZT
>----- Original Message -----
>From: Kevin Stover
>To: Writelog@contesting.com
>Sent: Friday, July 06, 2001 5:03 PM
>Subject: [WriteLog] Parallel Interface
>
>
>Hello all.
>In response to my last message it was suggested that I use an opto-isolator
>in the parallel interface to the rig to absolutely isolate the computer from
>the rig.
>Can I swap out the 2n2222 in the parallel circuit for the 4n33 of the serial
>in the documentation.
>Either way this circuit is going to have to drive the grid block keying
>circuit of my last post.
>
>Writelog documentation: http://www.willinet.net/~kstover/cwint.jpg
>
>Grid block keying circuit: http://home.att.net/~jacksonharbor/gridbsch.pdf
>
>Thanks for the input.
>
>Kevin, NØRKX
>


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