Can I superimpose a low voltage AC signal along a 24VDC line and then demux it back out? I am planning an analog / digitally switched intercom system. How will this be done?
Can I superimpose a low voltage AC signal along a 24VDC line
Yes.
and then demux it back out?
No.
What you need to do is to AC couple onto the line, that is just connect your signal into the line with a capacitor. To get it back you again use a capacitor, and then feed your device that needs the D.C. from that point through an inductor.
This is exactly how LNBs are controlled on a satellite dish, or intocoms over mains wiring.
mattlogue:
Can I superimpose a low voltage AC signal along a 24VDC line and then demux it back out? I am planning an analog / digitally switched intercom system. How will this be done?
What kind of signal? Audio? What frequencies/bandwidth? Amplitude? Is it just signal or is it meant
to power a speaker?
What is the nature of the DC load on the 24V (ie could it generate noise that would interfere with your signal?).
What is your 24V power supply (ie could it generate noise that would interfere with your signal?)
Hello,
Telephones as well as Phantom Power microphones operate in the same way:
Phantom Power microphone:
Phantom Power microphone detail:
Telephone Circuit Diagram:
But the phone line is a bit more complex than the Phantom power, because it also has the buzzer. And the phone line provides about 30mA in short, while the Phanton Power line provides about 7mA per channel (two-way + GND)
I may just run an extra line if it'll be as complex as the phantom microphone. Wire is cheap and I am now worrying about noise and interference.
mattlogue:
I may just run an extra line if it'll be as complex as the phantom microphone. Wire is cheap and I am now worrying about noise and interference.
The microphone (XRL) system is better than the phone because it operates with balanced lines, and the phone is unbalanced, so we have more noise on the phone.
But shielded cables are also used for the microphone, while only braided cables are used in the phone.
mattlogue:
I may just run an extra line if it'll be as complex as the phantom microphone. Wire is cheap and I am now worrying about noise and interference.
rtek1000 is making things way way more complicated than is needed. Don’t let him put you off.
Grumpy_Mike:
rtek1000 is making things way way more complicated than is needed. Don’t let him put you off.
Oh, sorry!
I'd use a couple of audio transformers, assuming you aren't drawing a lot of current. 1k to 8 ohms, then 8 ohms to 1k. That has worked for me, with straight audio.
Although you aren't really clear what signals these are. Just straight audio, analog voice signal?
It would help us, to help you, if you describe what it is you are trying to do.