Re: Remote Power Supply Connection

"Trevor Wilson" <trevor@[EMAIL PROTECTED]
> wrote in message 
news:69bqsaF321ke3U1@[EMAIL PROTECTED]
>> Lets face it the whole safety thing can be fixed. You put the
connectors 
>> at each end under covers. The covers can only be lifted by removing a 
>> screw (or two), under the cover is a micro switch. Long before anybody 
>> can access the actual connectors, the power is switched off by the 
>> microswitch. I have seen this on a number of pieces of professional 
>> equipment, for the safety of both the operator and the equipment
itself.
>
> **Except that such a solution only works with AC. DC power requires that

> capacitors be discharged as well (I need not remind you that
microswitches 
> are spectacularly unsuited for high Voltage DC).
>
> AC power cables make far more sense. Using DC is dumb.

Use some sense Trevor, you do not switch the power with the micro-switch, 
you use it to energise a relay or relays.

 Let me spell it out for you - you supply an unswitched low voltage from
the 
power supply to the amp. That pulls in a relay that connects the B+ input 
pin(s) to the B+ line in the amp. This voltage is fed back through the
cable 
to a similar switch in the power supply. When both switches are made 
(optionally after a delay) a relay is pulled in in the power supply which 
applies B+ to the cable. If either micro-witch is opened then power is 
dropped isntantly to both relays. Simple enough?

If you can open either cover, pull the cable and stick it in your mouth
fast 
enough to beat the relays, then you deserve what you get. It also prevents

arcing from trying to pull the cable under power.

I have seen this sytem used in a number of pieces of professional
equipment. 
If the gear uses serious amounts of DC power, you have no alternative to a

separate power supply and transferring DC over a cable.

Keith