Author Topic: Speaker protect circuits.  (Read 637 times)

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Offline nigelwright7557

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Speaker protect circuits.
« on: July 26, 2019, 01:14:29 am »
As  I build a few amplifiers after nearly blowing up a speaker after one had a fault I came up with speaker protect circuit.
It just drops out a relay if it detects dc in the signal to the speaker.
I used a PIC12F509. I used 2 pins to detect the phase of the audio signal.
I also added a power up delay for the relay.

I then progressed the design to a solid state relay with dc detect, over current detect and power up/down detect.
I designed the pcb myself using PCBCAD360.


PCBCAD51/PCBCAD360/PCBCAD720 PCB design software https://www.murtonpikesystems.co.uk
 

Offline Rick Law

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Re: Speaker protect circuits.
« Reply #1 on: July 26, 2019, 02:45:10 am »
I am not as experienced as most here, but I have seen a number of PCB in photo attachments here - tens of dozens probably.

I must congratulate you.  I found your board very aesthetically pleasing.  It is very nice to look at.
 

Offline nigelwright7557

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Re: Speaker protect circuits.
« Reply #2 on: July 28, 2019, 09:27:37 pm »
I am not as experienced as most here, but I have seen a number of PCB in photo attachments here - tens of dozens probably.

I must congratulate you.  I found your board very aesthetically pleasing.  It is very nice to look at.
My only criticism of the pcb is the size.
It really needs to be smaller to fit in the enclosure with the amplifer.
My latest revision is a bit smaller.
PCB was done with PCBCAD360.
PCBCAD51/PCBCAD360/PCBCAD720 PCB design software https://www.murtonpikesystems.co.uk
 

Offline bob91343

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Re: Speaker protect circuits.
« Reply #3 on: July 28, 2019, 10:14:07 pm »
Is relay dropout fast enough?  I would add a closure to short the speaker as well.  One major spike could still get through.

But yes, a nice job.  I have never been able to get myself into fabricating PC boards but would like to.  The software always seems awkward and often the libraries lack some devices I need.  Do you use ferric chloride?  Or do you just buy the boards?
 

Offline nigelwright7557

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Re: Speaker protect circuits.
« Reply #4 on: July 28, 2019, 10:27:02 pm »
Is relay dropout fast enough?  I would add a closure to short the speaker as well.  One major spike could still get through.

But yes, a nice job.  I have never been able to get myself into fabricating PC boards but would like to.  The software always seems awkward and often the libraries lack some devices I need.  Do you use ferric chloride?  Or do you just buy the boards?

Its a solid state relay, the mosfet's  drop out in micro seconds.

I only buy in pcb's from China. I can get 10 pcb's 10cm by 10cm for $5 plus p+p.
I often buy in a few different pcb's so the cost of p+p is shared out among them.
p+p is only expensive if you get 3 day delivery.
I use PCBWAY and JLCPCB.
PCBCAD51/PCBCAD360/PCBCAD720 PCB design software https://www.murtonpikesystems.co.uk
 


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