NEWBIE - Power supply to multiple relays

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Looking at PRR's simple relay design
underthotrelay.gif

I am planning to use 7 relays in the Calrec circuit (I think)
I have a 24V DC power supply coming in just for the relays..

Is it okay just to split the 24v line 7 times before I feed each relay 24V and then use a common ground

The reason I ask is that .. if I do that and press down on one of my SPST pushbuttons will it affect the other relays - or am I thinking too much?

I am replacing the resistor and LED with a 24v lamp (inside the pushbutton - a EAO series 19 locking switch)

one more question...
one of my relays (a 4PCO has an earth pin - do I connect this at all? the other one a 2PCO doesn't have one)
 
Hi,

As long as the power supply can deliver enough current to keep all the relays you'd likely need "on" at any one time, yes, you can just split the incoming supply to the seven relays. Make sure that you keep the ground for the relays separate from the audio ground until it reaches your PSU common terminal.

Also add some back-emf suppression diodes to each relay coil individually- use a 1N4003/4 etc connected directly across the relay coil close to the relay pins. The diode is connected backwards w.r.t the current flow- i.e. cathode to +Ve supply, anode to 0V. This helps prevent any large voltage build up from the falling magnetic field in the relay coils, plus extending the life of your switches from arcing.

When using lamps- make sure your PSU can supply enough current to light them all- they can be quite current-hungry compared to LED's!

The ground pin on the relay- where in the circuit are you switching? If it's a low level signal, it may be worth connecting it to 0V. Sometimes the ground pin connects not only to the case, but an internal screen between the coil and contacts which can help keep any interference from coil to contacts low. Try it and see- you can always solder it in as a link!

Mark
 
Thanks guys....
Am half way through designing the PCB and am powering it from a 30VA transformer (just for relays and lamps in all my projects) - me think I had better look up the requirements
 

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