Ac interference

[GalaxyGuy]

Just now, al-yeti said:

But audio is still ac 

 

What's your definition of audio?   A speaker makes a noise because the diaphragm is driven in and out by the voice coil. An AC signal will drive the speaker coil in both directions rapidly at various changing frequency, thus giving audible sound. By just switching the diaphragm between one direction and rest, at various frequency, as in pulsed DC, you will also generate audible sound.

[al-yeti]

2 minutes ago, GalaxyGuy said:

 

What's your definition of audio?   A speaker makes a noise because the diaphragm is driven in and out by the voice coil. An AC signal will drive the speaker coil in both directions rapidly at various changing frequency, thus giving audible sound. By just switching the diaphragm between one direction and rest, at various frequency, as in pulsed DC, you will also generate audible sound.

Audio is ac basically, I am not questioning the DC output drive on a panel , but audio signal itself is ac ?

[GalaxyGuy]

18 minutes ago, al-yeti said:

But audio is still ac 

 

What's your definition of audio?   A speaker makes a noise because the diaphragm is driven in and out by the voice coil. An AC signal will drive the speaker coil in both directions rapidly at various changing frequency, thus giving audible sound. By just switching the diaphragm between one direction and rest, at various frequency, as in pulsed DC, you will also generate audible sound.

[al-yeti]

1 minute ago, GalaxyGuy said:

 

What's your definition of audio?   A speaker makes a noise because the diaphragm is driven in and out by the voice coil. An AC signal will drive the speaker coil in both directions rapidly at various changing frequency, thus giving audible sound. By just switching the diaphragm between one direction and rest, at various frequency, as in pulsed DC, you will also generate audible sound.

Yes but makes no difference going in circles with this speakers are AC and audio is generally ac 

 

Maybe go through all the theory again instead of looking at an alley no offence .....

 

 

[GalaxyGuy]

1 minute ago, al-yeti said:

Yes but makes no difference going in circles with this speakers are AC and audio is generally ac 

 

Maybe go through all the theory again instead of looking at an alley no offence .....

 

 

 

So, how does the current change direction on an output that can only switch from +12v DC to 0v ?   

 

Ah, I see that you've changed to "generally ac" now.

[al-yeti]

16 minutes ago, GalaxyGuy said:

 

 

 

Ah, I see that you've changed to "generally ac" now.

This is a discussion forum I thought 

 

 

[james.wilson]

If using pulsed dc drive you would only have half throw so less volume than ac drive? 

[GalaxyGuy]

1 hour ago, al-yeti said:

This is a discussion forum I thought 

 

 

 

Yes, indeed.   In the context of the original question, the point is moot, as both AC and DC can cause interference with the 'circuit' signal. In the case of the differential pair of the RS485 bus, this is less of an issue, as it's the differential that's important and as both wires are impacted by the same external noise, the data signal isn't impacted.  The problem usually comes with mains based signals where heavy currents drawn by mains based appliances can cause huge induced voltages in nearby cables, that can damage the bus drivers and the analog to digital multiplexers that read zone voltages. The actual zone voltages can also be disturbed, causing nasty false alarms that can be really difficult to diagnose.  

 

I'm not sure if there's enough current driving the alarm speaker to cause any issue, but if the manufacturer advises against it, then it's probably based on some measurement or experience of a problem in the past.

 

15 minutes ago, james.wilson said:

If using pulsed dc drive you would only have half throw so less volume than ac drive? 

 

Yes.

[sixwheeledbeast]

Getting back on topic...

It's not good practice to run speaker circuits within the same cable as other circuits. I don't believe there is a rule for this apart from some manufacturers say you must not do it.

Main concern in the wild is normally the other way, as in getting annoying data noise from bus devices out of your speaker.