I have a plethora of these relays at my disposal:
NAIS JS-M-1a-12V-4 relay datasheet
And I also have a few of these:
Omron LY2-UA-006244 DPDT 120Vac coil
So I thought I would try to put them to use to disconnect my drivers from my amplifier when the AC mains is switched off (and then re-connect them when the AC is switched back on).
The idea is to use the 120Vac relay contacts to short the coil(s) of the other relays (that are making/breaking the loudspeaker-amplifier connections). The DC driving current for the JS-M relay coils is obtained from the power amp rails via a series resistor. This allows enough current to flow through the coils that the relay pulls in reliably. The 120VAC coil LY-2 relay contacts are normally closed, and when the relay is energized by AC these open, and current flows only through the coils of the JS-M speaker disconnect relays. When AC is switched off, the JS-M coils are shorted by the contacts of the LY-2 relay and the power stored in the caps drains. Of course a power resistor must be used for the current setting resistor. I use a 10W, with an actual dissipation when the amp is "on" of a little over 2W, increasing to a peak of 3.5W when the AC is turned off and the rail start to drain. I may also add a second "drain resistor" for the rail using the other contacts of the LY-2 relay. The amp uses so much capacitance that it can keep playing for about 1 minute at modest volume if the caps are not drained by any other means.
What I like about this circuit, apart from using parts that I had lying around, is that there shouldn't be any flyback EMF from the relay coil when it is connected or disconnected. Thus, no suppression is needed. Also, it switches on/off in 10-20msec or so and does not need auxiliary voltages. It does use an extra relay and that does represent additional cost. Apart from that, I would like to know if this circuit has any flaws or drawbacks (I can't find any really), or if you have any other general comments please post. Thanks.
See attached circuit drawing.
NAIS JS-M-1a-12V-4 relay datasheet
And I also have a few of these:
Omron LY2-UA-006244 DPDT 120Vac coil
So I thought I would try to put them to use to disconnect my drivers from my amplifier when the AC mains is switched off (and then re-connect them when the AC is switched back on).
The idea is to use the 120Vac relay contacts to short the coil(s) of the other relays (that are making/breaking the loudspeaker-amplifier connections). The DC driving current for the JS-M relay coils is obtained from the power amp rails via a series resistor. This allows enough current to flow through the coils that the relay pulls in reliably. The 120VAC coil LY-2 relay contacts are normally closed, and when the relay is energized by AC these open, and current flows only through the coils of the JS-M speaker disconnect relays. When AC is switched off, the JS-M coils are shorted by the contacts of the LY-2 relay and the power stored in the caps drains. Of course a power resistor must be used for the current setting resistor. I use a 10W, with an actual dissipation when the amp is "on" of a little over 2W, increasing to a peak of 3.5W when the AC is turned off and the rail start to drain. I may also add a second "drain resistor" for the rail using the other contacts of the LY-2 relay. The amp uses so much capacitance that it can keep playing for about 1 minute at modest volume if the caps are not drained by any other means.
What I like about this circuit, apart from using parts that I had lying around, is that there shouldn't be any flyback EMF from the relay coil when it is connected or disconnected. Thus, no suppression is needed. Also, it switches on/off in 10-20msec or so and does not need auxiliary voltages. It does use an extra relay and that does represent additional cost. Apart from that, I would like to know if this circuit has any flaws or drawbacks (I can't find any really), or if you have any other general comments please post. Thanks.
See attached circuit drawing.
Attachments
Everyone is speechless I guess...
I'm using this setup in a pair of active speakers. Works like a charm.
I'm using this setup in a pair of active speakers. Works like a charm.
If the 35Vdc supply has large capacitors.....
It looks like the speakers remain vulnerable until the 35Vdc Caps can discharge through 330ohms to ground.
Another option would be to use one DP relay to select between OFF shunt connecting the speakers relays directly to ground for a QUICK DISCONNECT, or to ON connect the speaker relays to 35Vdc through a second properly sized "relays current only" resistor.
Use the second SP relay to connect the 35Vdc through a slow discharge second sized resistor to ground when AC is off. Probably no reason to early burn out the relay contacts with a fast discharge of the 35Vdc.
Attachments
Sorry, can't get your point. At this moment, the AC relay will be shortening the supply for the two series DC coils, so that they will be off. It looks like the speakers will be disconnected from the amplifier...
This is exactly the case. When the AC mains is removed, the relay "Omron LY-2" closes its contacts (they are marked NC after all) and shorts across the coils of the JS-M relays. The JS-M contacts immediately open.
I have been trying this setup for about a week now. The drivers have silently disconnected each time the power was switched off.
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