vigyanabikshu
Member level 1
- Joined
- Oct 2, 2008
- Messages
- 32
- Helped
- 5
- Reputation
- 10
- Reaction score
- 5
- Trophy points
- 1,288
- Location
- KERALA, INDIA
- Activity points
- 1,528
If you design it properly, “it will work fine”. Long duration pulses? Low noise environment?
But why PWM, Why not a single pulse of a specific duration? Why a whole microcontroller when you could do this with an RC circuit and a comparator?
And how do you turn a speaker off?
I would suggest a far similar system: Keep the wiring as it is but instead of using PWM, use a simple two byte serial stream. Byte one to identify loudspeaker 0 through loudspeaker 255 and byte two to select or deselect it. The advantage is it is easier to send serial data than PWM over long lengths, the data only needs to be sent when selecting or deselecting a loudspeaker and it allows for multiple selections at once. Most MCUs already have UARTs in them so you probably don't need any additional hardware. You also get some spare bits of data to use for other purposes, maybe to flash an alert light on the selected loudspeaker or set volume level.
With care you can even use the same wires for audio as for control!
Brian.
Thank you very much for your valuable suggestion. But I am confused with UART will reliably work over some 200mtrs and for some 25 MCU slaves simultaneously.
I agree about using RS-422 or RS-485. It can work over many km in a party line topology with correct end termination.
I'm however surprised that you are planning 200 m regular speaker cable, apparently with low ohmic speakers. Most people would used constant voltage over this distance, 200 m low impedance cabling gives considerable power and particularly high frequency loss. See https://en.wikipedia.org/wiki/Constant-voltage_speaker_system
Sending the data over the audio cable is an interesting idea, but would require modulation to avoid audible interferences. A power line modem chipset is an obvious option. Effort is of course considerably higher than separate data line, could make sense if you are working in an existing public address infrastructure.
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?