Goal: feed audio from a PC to a circuit that will trigger a relay

Thread Starter

DavidDavidScollay

Joined Dec 5, 2021
25
1. With D1 removed the relay does not engage
2. the resistor colors are just the camera. I measure all my resistors and this one measured 33k
3. FYI am using 1n4002 diodes (it's what I had in my parts drawer) but that shouldn't make a difference, should it?
 

sghioto

Joined Dec 31, 2017
3,071
1n4002 is OK. Need to get out your voltmeter and make a few readings to see where the problem is if you have time.
Disconnect the audio from the PC and read the voltage on the collector of Q1 to start. It should read appx .1 to .2 volts.
 

sghioto

Joined Dec 31, 2017
3,071
That's a problem. Remove D1 to separate the two transistor circuits. Read the voltage on the base of Q1 it should read appx .7 volt
 

sghioto

Joined Dec 31, 2017
3,071
Something is not right. Remove the big blue capacitor so I can see the connections to Q1 and Q2 on the breadboard.
With D1 removed was is the voltage on the collector of Q1?
 

Thread Starter

DavidDavidScollay

Joined Dec 5, 2021
25
.693v so pretty much.7
Hold the phone. The 220 K resistor R2 was not making a clean connection to the plus supply.

So that solved the problem of the circuit going immediately into transmit upon power up. Now what is happening is when I send audio from the laptop the relay engages and disengages rapidly I’ll try to take a video so you can hear the sound
 

sghioto

Joined Dec 31, 2017
3,071
There might be a short gap between the pulses or the 22uf cap is not installed correctly.
Do you have a scope to see the audio from the PC?
 

Thread Starter

DavidDavidScollay

Joined Dec 5, 2021
25
I think we got it. It needed more volume from the PC to keep the relay engaged. I also needed to adjust the Mic input on the radio. I am transmitting unfortunately on this particular frequency there isn’t much activity at night.

I’m going to play around with this tonight. I really really appreciate the time you have taken to help me troubleshoot this. I’m wicked impressed
 

Thread Starter

DavidDavidScollay

Joined Dec 5, 2021
25
Here is a video of the circuit in action. You don’t hear the tones of FT8 because I haven’t added the speaker to the circuit. But you can see the computer going into transmit mode and hear the clicking of the relay and you see that the transmitter is operating and being received by a station which reports on a website


 

Thread Starter

DavidDavidScollay

Joined Dec 5, 2021
25
Nice. Are you satisfied with the circuit or does it need any improvements?
this particular band suffers in the winter months due to atmospheric conditions at this frequency. I know I am transmitting because I can see my call sign being spotted on the website and I am receiving stations but I have yet to make an actual contact.

Once I make a few connections with other hams then I will have a better sense of what needs to be added. But it seems to be working fine right now. Thank you again so very much for your assistance
 

Thread Starter

DavidDavidScollay

Joined Dec 5, 2021
25
Nice. Are you satisfied with the circuit or does it need any improvements?
no sooner did I click send on my last post did I make the first of two connections using the interface. Attaching a screenshot of what it looks like on the computer went to ham radio stations exchange location and signal reports. So it works!
 

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Thread Starter

DavidDavidScollay

Joined Dec 5, 2021
25
Nice. Are you satisfied with the circuit or does it need any improvements?
well now I have to report unfortunately some thing has happened and I am not getting the right level of audio out of the circuit to drive the transmitter. The attached picture of the scope is what I see coming into the circuit from the laptop, what I see coming out of the transformer, and what is going to the radio. The laptop is sending the maximum level of audio that it can which is what I need to trigger the relay.
 

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MisterBill2

Joined Jan 23, 2018
11,640
In ham-speak, the function desired is called "vox", short for Voice Operated Transmit. That sort of circuit has been published in every Radio Amateur's Handbook since the early 1980's and is fairly well designed. It uses a quad opamp, a 555 timer IC, and a single transistor, and will run on 12 volts. The circuit in this thread will also work, but the value of C2 will need to be reduced.
And the power and common connections as shown will be a bit confusing.
 

Thread Starter

DavidDavidScollay

Joined Dec 5, 2021
25
In ham-speak, the function desired is called "vox", short for Voice Operated Transmit. That sort of circuit has been published in every Radio Amateur's Handbook since the early 1980's and is fairly well designed. It uses a quad opamp, a 555 timer IC, and a single transistor, and will run on 12 volts. The circuit in this thread will also work, but the value of C2 will need to be reduced.
And the power and common connections as shown will be a bit confusing.
Do you have a link to this circuit? I like the 555 it’s an old friend
 
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