Samuel Groner

    Zürich, Switzerland
  • Posts: 2935
"Balanced Power" For Relays
« on: September 24, 2006, 01:05:38 PM »

Just thought that it would be possible to power relays from e.g. +/- 12 V supply lines instead of a single 24 V. That would make our beloved ground essentially free from any switching currents (even more free than just running a separate relays ground), which might help a good deal for low-level swiching (mic preamp) or for large systems (console). The only disadvantage I see at the moment is the more complex PSU. Any thougths? Allready done?



"Balanced Power" For Relays
« Reply #1 on: September 24, 2006, 01:33:04 PM »
The -12V line in a +/-12V system would carry exactly the same noise as a dedicated "dirty ground" line in a +24V-only system, wouldn't it..?

Jakob E.
..note to self: don't let Harman run your company..

Samuel Groner

    Zürich, Switzerland
  • Posts: 2935
"Balanced Power" For Relays
« Reply #2 on: September 24, 2006, 02:59:59 PM »
Yep, but the balanced lines are not directly connected to any other ground (as is the "dirty ground"), only by the ground reference of the regulators/center tap. This might remove any chance to modulate things, right?

Sure, if you do it right, the standard way works.



"Balanced Power" For Relays
« Reply #3 on: September 25, 2006, 11:27:51 AM »
if you're working in a fixed system, where you cannot be sure of the "quality" of your ground, then yes, hanging your relays (and LEDs, etc) between the bipolar rails will stop it from modulating the ground when switched.

another option, which i've not tried, but seems like it could work, is to assign a current source, delivering the max current needed by your relay or LEDs, for each device or chain of devices.  this is terribly wasteful of power, but at least when the devices kick on and then off, there isn't a spike in current draw.



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