Portsdown 4 sequencer

[Rishtonite]

Am I correct in thinking the following would work...
GPIO pin 40 feeds the LED of optoisolator (standard or darlington?) and the output arrangement is like the attached screen grab,
but with 12v, not 24v, and (in the image) the motor is replaced by a small SPDT relay which is connected to act like the TX/RX switch in the G8ADE
sequencer circuit (CQ-TV 125)

[gm1mfn]

That circuit is more complicated than necessary and lacking a vital component. A relay is an inductive device and there should be a reverse diode across the coil to dump the back-EMF when switching off.

This is what you should use:

[Rishtonite]

Thanks for the comments and new diagram. After posting I did think more about it and realised it wasn't the best solution.
Is "V in" straight from pin 40, no opto ??

[radiogareth]

Yes, that's right, via the 1k resistor. Its what I use for my 'PTT' control, both Portsdown and Langstone have a 100mSec delay after making that pin high before any RF is emitted.
Gareth

[Rishtonite]

Thanks.
Testing my (not fully wired yet, pluto with stubby antennas, no Power amp) system I checked with testcard selected, pressed TX on the Pi screen and it took about 3 seconds for 3.3v to appear on pin 40 of the Pi header.
Unless I've misunderstood the coment about 100mS, from your comments that sounds like it's wrong.
Or maybe the 3 seconds is correct, then it takes another 100mS for Pluto to start TXing?
I'm confused when I look at the functions of other pins. For working 23cm (only) should there be any other header pins taken hi or lo (via a resistor?)