ok thanks now here is one as I don't want to have to take this whole board apart and start over here is the diagram I am using for my relay based keyer the reason for the 2 transistors is the ttl board has the RTS line high when not in use. can I simply replace Q2 with a PC187 opto or is there more involved? I have just never really used these things before other than replacing blown ones.

Thanks,
Yonu

 

hi,
You could replace Q2 with an opto, the 300R would drive the opto emitter, [ check the opto d/s to ensure that the 300R will supply the required current].
BUT
the output of the opto will not be able to drive a relay directly, you will most likely need a transistor on the output of the opto to drive a relay.

Post a circuit diagram showing the purpose of the opto.?
E

 

I will redo the calculations on the resistor to make sure I had planed on that. I can post a circuit if you like but the sole purpose of the relay in that diagram is to short the radio ptt line to the radio ground. I had planed on omitting the relay in this design to cut down on the size of the board and simply use the opto to short the connections.

Thanks,
Yonu

 

hi yon.
The opto output will not short the connections, use a open collector transistor on the output of the opto.

 

drats ok was under the impression from some of the diagrams on Ham site to opto could directly short the ptt on a transistor based rig.

 

ok while I am waiting on the audio components I am working on the board installing the sockets and soldering the components I have a odd question I am adding 2 10k pots for the audio tx/rx levels. I assume thet should be on the pc side?

Thanks,
yonu

 

drats ok was under the impression from some of the diagrams on Ham site to opto could directly short the ptt on a transistor based rig.

The UK magazine; Practical Wireless has run various articles about opto-isolating PTT inputs etc.

Might be worth checking their website to find a email to ask someone - but they might want you to order back issues or photocopies of articles.

 

crutschow on your diagram I have a couple question as I had more parts on hand than I thought is V3 the incoming audio signal? can I use a pc817 opto I have a few of them? and for v2 my incoming voltage will be 8 or 12vdc how do I recalculate the resistor value?

Thanks,
Yonu

 

Well I did a bit of research guess I will order a couple of the optoa you listed in the diagram if I understand the datasheet right the pc817 is slower

Thanks,
Yonu

 

crutschow on your diagram I have a couple question as I had more parts on hand than I thought is V3 the incoming audio signal? can I use a pc817 opto I have a few of them? and for v2 my incoming voltage will be 8 or 12vdc how do I recalculate the resistor value?

Yes V3 is the incoming audio signal.

Even if the pc817 is a little slower it should still be okay for voice frequencies.

Increase the value of R1 in proportion to the supply voltage. Thus for 8V, it should be 8/5 * 600 = 960 ohms. Of course, as I previously noted, you may have to adjust it's value to get the output voltage level you want. Increasing the value of R2 will also increase the gain.

 

Ok then you just awnsered another question I have of where to put my adjustment pots at least I think so could I just put it on R2. or should i put it In the audio line?

Thanks,
Yonu

 

Ok then you just awnsered another question I have of where to put my adjustment pots at least I think so could I just put it on R2. or should i put it In the audio line?

What is the purpose of the adjustment? Is it a one time thing to initially adjust the levels or will you be adjusting it for different signal levels during the equipment usage?

 

it depends I have started using a new piece of software for digital modes that seems to be real picky so more than likely I will have to be adjusting some while in use.

Thanks,
Yonu

 

ok I have started putting the board together however I even made a trip to the local unradio shack to see if they had closer resistors than what I had and they didn't the closest I had was 22k and 560ohm I notice you specified 20k and 600ohm in the diagram. should I beable to assume the are close enough or do I need exact?

Thanks,
Yonu

 

22k and 560 ohm should be fine.

 

sorry for just getting around to responding I finally got time to put the diagram you provided put together it does fine on voice and RTTY and it doesn't have the audio range for MT-110A digital mode. and since I have had to redue my board as the usb-serial adapters I had order were actually larger than the listed specs I got to thinking would A IR audio transmitter like is in IR headphones offer more of a audio range?

Thanks,
Yonu