Hi Andrew
Just had a closer look at your SSLR document and a question occurred. Checked the first 250~300 posts in this thread but didn't see it discussed so here it is.
Your latest SSLR is switched in the return line. Won't this mean there is no protection if the active line is accidentally shorted to earth?
Best wishes
David
Just had a closer look at your SSLR document and a question occurred. Checked the first 250~300 posts in this thread but didn't see it discussed so here it is.
Your latest SSLR is switched in the return line. Won't this mean there is no protection if the active line is accidentally shorted to earth?
Best wishes
David
Yes, but I assume one has the sense not to do that . . . 🙂
Note that the SSLR is the switch part only - it does not cover the sensing part.
For the ultimate in simplicity, just sense the ground return current and then activate the switch part. If you think shorting the hot speaker lead to the chassis a real potential problem, then simply sense the hot lead current and then activate the switch part.
On the e-Amp, I sense the current across the output stage degen resistors using an opto. You can use a similar technique with the ground return SSLR.
Looks like I should add a few application diagrams to my article to clarify these points.
Thanks for the observations - I appreciate it.
Note that the SSLR is the switch part only - it does not cover the sensing part.
For the ultimate in simplicity, just sense the ground return current and then activate the switch part. If you think shorting the hot speaker lead to the chassis a real potential problem, then simply sense the hot lead current and then activate the switch part.
On the e-Amp, I sense the current across the output stage degen resistors using an opto. You can use a similar technique with the ground return SSLR.
Looks like I should add a few application diagrams to my article to clarify these points.
Thanks for the observations - I appreciate it.
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check out post #13 about
http://www.diyaudio.com/forums/pass-labs/160416-threshold-amps-dc-protected-2.html
for my favorite solution
other approaches without relays are follow:
http://www.diyaudio.com/forums/elektor/11523-elektors-ulti-amp.html (post #4)
http://www.diyaudio.com/forums/solid-state/155939-mosfet-relais.html
http://www.diyaudio.com/forums/solid-state/20745-another-simple-dc-protection.html
a reasonable approach by the use of relays are two relays in parallel mode, e. g. two of this one (go to number 4 about "features"):
http://www.panasonic-electric-works.de/catalogues/downloads/relays/ds_61005_0001_en_ds.pdf
but with different times of activation of the coils.
more relais for audio:
http://www.diyaudio.com/forums/solid-state/153935-best-audio-relays.html
P.S. until this day nobody could me provide an evidence, that a top quality electrolytic capacitor between the amplifier output and speaker-terminal is an audible disadvantage.
Theoretically, this represents of course an unwanted high-pass function.
Nevertheless - for most today's speakers this effect is rather advantageous.
http://www.diyaudio.com/forums/pass-labs/160416-threshold-amps-dc-protected-2.html
for my favorite solution
other approaches without relays are follow:
http://www.diyaudio.com/forums/elektor/11523-elektors-ulti-amp.html (post #4)
http://www.diyaudio.com/forums/solid-state/155939-mosfet-relais.html
http://www.diyaudio.com/forums/solid-state/20745-another-simple-dc-protection.html
a reasonable approach by the use of relays are two relays in parallel mode, e. g. two of this one (go to number 4 about "features"):
http://www.panasonic-electric-works.de/catalogues/downloads/relays/ds_61005_0001_en_ds.pdf
but with different times of activation of the coils.
more relais for audio:
http://www.diyaudio.com/forums/solid-state/153935-best-audio-relays.html
P.S. until this day nobody could me provide an evidence, that a top quality electrolytic capacitor between the amplifier output and speaker-terminal is an audible disadvantage.
Theoretically, this represents of course an unwanted high-pass function.
Nevertheless - for most today's speakers this effect is rather advantageous.
But if everyone had sense we wouldn't need protection😉.
It's not a real concern for my application (or yours), but I would expect for professional units that accidental shorts to the chassis would be second only to cable shorts.
I am more inclined to put the SSRs in the power lines from the supply capacitors.
Use them to protect the speaker from the amp and the amp from low impedance and also replace the usual line fuses. Would still work if the speaker cable was shorted to the chassis. And one wouldn't have to try to convince people that the distortion of the FETs is practically nil😉
And simply don't connect the power to the amp 'til it is stable and with a balanced power supply there should be no thump.
Best wishes
David
I'll draw up some circuits to show how this can be done and add them to the doc- I'll need a few days though - very busy at the minute.
Im in need of a on delay dc speaker protect,
Ill be using relays,
So many threads on this so I decided to post here instead of new one.
Im in need of a small but nice working circuit and board if someone can advice,
Stereo or seperate channel protection is ok, amplifier is 100W into 8R.
Relay Question:
I have these relays and would like to know if they would be up for the job.
I have plenty (25+) and can use one per speaker ( 2 sets of contacts per speaker) and another relay for on delay.
Regards
Tyco (SCHRACK) RT424024
http://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Data+Sheet%7FRT2%7F0511%7Fpdf%7FEnglish%7FENG_DS_RT2_0511.pdf
Ill be using relays,
So many threads on this so I decided to post here instead of new one.
Im in need of a small but nice working circuit and board if someone can advice,
Stereo or seperate channel protection is ok, amplifier is 100W into 8R.
Relay Question:
I have these relays and would like to know if they would be up for the job.
I have plenty (25+) and can use one per speaker ( 2 sets of contacts per speaker) and another relay for on delay.
Regards
Tyco (SCHRACK) RT424024
http://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Data+Sheet%7FRT2%7F0511%7Fpdf%7FEnglish%7FENG_DS_RT2_0511.pdf
Vostro,
For DC speaker protection, if you use a mechanical relay, the contacts need to be DC-rated, the one you plan to use has contacts designed for AC only. If you used that one and had a DC fault occur, the contacts could weld themselves together and fail to open, which would then allow your speakers to fry. I haven't used mechanical relays for years, I'll only use MOSFET based solid state relays for speaker protection.
Mike
For DC speaker protection, if you use a mechanical relay, the contacts need to be DC-rated, the one you plan to use has contacts designed for AC only. If you used that one and had a DC fault occur, the contacts could weld themselves together and fail to open, which would then allow your speakers to fry. I haven't used mechanical relays for years, I'll only use MOSFET based solid state relays for speaker protection.
Mike
Hi,
Just in case somebody it is interesting in built one. Attached it is a link to my thread.
http://www.diyaudio.com/forums/chip...ng-speaker-output-using-microprocessor-6.html
Just in case somebody it is interesting in built one. Attached it is a link to my thread.
http://www.diyaudio.com/forums/chip...ng-speaker-output-using-microprocessor-6.html
Thanks Mike,
Ill look for a ss relay circuit and pcb then.
@tauro0221 Ill have a look at your design for some tips,
and see If I have the time to make a PICmicro one for myself.
Time doesnt seem to last as long as it used to.
Ill look for a ss relay circuit and pcb then.
@tauro0221 Ill have a look at your design for some tips,
and see If I have the time to make a PICmicro one for myself.
Time doesnt seem to last as long as it used to.
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Any body that wants to use my design are welcome. Since the programming it is already done. The only thing to do it is to change some parameters to run in any system. So that means if you make the board I will program the microprocessor and the only thing you will pay me it is the cost of the microprocessor. I have one that run using a 24 volts relay already. But I will recommended to use the current sensor with solid state relay. It is more simple to built. There are current sensor from 5, 12, 20, 30, 50, and 100 amps. It can be stand alone or build in into the amplifier either way works for me. The boards are design using the ExpressPCB software and can be modify to fit any requirements.
I have just updated the SSLR write up on my site and the associated PDF. I have included some thoughts on current sensing and also providing simple latching functions using a opto trial driver.
Hi Andrew.
Just had a look at the updated PDF on your site. Another fine contribution.
Still don't think it fixes my concern however.
If you "simply sense the hot lead current and activate the switch part" then the system will correctly detect a hot lead short and activate the switch, but this won't help because the switch is only in the return lead.
Has one of us has missed the obvious?
Best wishes
David
Dave, you are correct. The circuit will NOT protect against a speaker hot line short to the chassis. FTP protect against this fault mode, you need to switch the hot line. This is what I do in my e-Amp, using photo couplers. I will make this more explicit in my write-up.
Still appears like you are switching the gnd end in your e-amp just by looking at your protection schematic....
SSRs in rails
I am still inclined to put the FETs in the rails and protect the speakers that way.
This can also protect from internal faults and replace fuses.
Seems all I need to do is use PhotoVoltaic couplers and it will be very simple.
1. Will fail to safe if the PVs fail.
2. I can use same polarity FETs for both rails because the PV outputs float.
So why do Avago make PV couplers that seem to differ only in which way round the output pins are connected? (ASSR-V621 and ASSR-V622) Seems too trivial to be just for board layout.
Best wishes
David
I am still inclined to put the FETs in the rails and protect the speakers that way.
This can also protect from internal faults and replace fuses.
Seems all I need to do is use PhotoVoltaic couplers and it will be very simple.
1. Will fail to safe if the PVs fail.
2. I can use same polarity FETs for both rails because the PV outputs float.
So why do Avago make PV couplers that seem to differ only in which way round the output pins are connected? (ASSR-V621 and ASSR-V622) Seems too trivial to be just for board layout.
Best wishes
David
Putting fets at the rails fine except that I think there is still the likely chance of turn-on/off thumps. Best to try it and see....
Rlim, yes your are right. You need to delay the amplifier to the rails settle and then close the speaker output relay.
Turn on thump
A reasonable concern.
I think turn off should be OK, the outputs are disconnected from the power almost instantly.
Turn on is more of a concern. If the IPS and VAS are stabilized first then the connection of the outputs should be fine because it will be symmetrical.
Could take the power for the IPS & VAS from before the FETs perhaps?
Since their current draw is small it should be safe.
Extra FETs in sequence would work but seems overkill.
If power is simply connected to the rails then the OPS will already be powered as the small on-board filter capacitors of the IPS are ramped up. That could be OK if the IPS stays balanced. SPICE transient simulation needed.
Any other ideas?
Best wishes
David
A reasonable concern.
I think turn off should be OK, the outputs are disconnected from the power almost instantly.
Turn on is more of a concern. If the IPS and VAS are stabilized first then the connection of the outputs should be fine because it will be symmetrical.
Could take the power for the IPS & VAS from before the FETs perhaps?
Since their current draw is small it should be safe.
Extra FETs in sequence would work but seems overkill.
If power is simply connected to the rails then the OPS will already be powered as the small on-board filter capacitors of the IPS are ramped up. That could be OK if the IPS stays balanced. SPICE transient simulation needed.
Any other ideas?
Best wishes
David
Uh, I was here at page 2 but dropped out for awhile. As Mooly said on this thread www.diyaudio.com/forums/parts/217907-choosing-relay-loudspeaker-switching.html oxydized relay contacts can cause distortions on soft signals. So why, other than cost, don't designers use copper relay contacts between the supply rails and the output transistors. That seems to be a high energy point. I've got six "free" 3 pole 22 A 460 V contactors, AB 100-A12ND3. I'm going to try one on each side on the rails instead of the PCB land melting diac->triac speaker shorting circuit. I'm going to use the diac on each side to turn off the triac that turns on the relay.