Regulator with floating ground and speaker protection

Hi,

I'm building a regulated PSU based on LT1083 positive chip regulators. There is no negative counterpart so I'm using two of these chips with floating ground. Everything looks great except the speaker protection circuit. It doesn't like my floating ground and doesn't activate the relay. The circuit is powered from the main transformer trough a resistor divider to drop the voltage. Could I solve the problem using a second tranformer only for the speaker protection and connect one of the secondary wires to the floating ground?

Thank you.
 

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whizgeek

Member
2010-02-16 11:47 pm
On your protection circuit, you have ac inputs, with common ground. Is this the connection to the resistor divider?
This is whats upsetting the floating ground bit.

You only need to use the dc from one of the LT1083 regulators. +ve side as i presume the protection circuit ground is common to all the circuits.
Its only a few milliamps for relay current, so negligible loading. do you really need the 317 regulator?
Also is d4 good enough for relay current?
 
On your protection circuit, you have ac inputs, with common ground. Is this the connection to the resistor divider?
This is whats upsetting the floating ground bit.

You only need to use the dc from one of the LT1083 regulators. +ve side as i presume the protection circuit ground is common to all the circuits.
Its only a few milliamps for relay current, so negligible loading. do you really need the 317 regulator?
Also is d4 good enough for relay current?

I thought of that but I'll loose instant power off on AC loss.
 
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