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paulspencer 26th August 2005 08:13 AM

power supply transformer wiring question
 
2 Attachment(s)
I'm building this kit:

http://www1.jaycar.com.au/productVie...Max=&SUBCATID=

http://www1.jaycar.com.au/products_u...oduct_7082.jpg

It's a power up kit - where a master appliance switches on a slave when the master is powered up or down.

It has its own power supply, but I have come across something unclear. The schematic shows two 6.3V wires from the transformer to 4 diodes (bridge rectifier), however it does not show the 0V wire. The transformer supplied with the kit has this 0V wire, and I don't know if it needs to be hooked up somewhere, or if I can just plug it up.

0V wire in question is shown with a big black dot I added after scanning.

I have built power supplies before, so I'm not a total novice, but I had schematics that didn't leave anything out!

MY QUESTION: What should I do with the 0V wire from the transformer?

quasi 26th August 2005 01:30 PM

This wire is most likely the center tap of the secondary winding. Just insulate the end and tuck it in somewhere out of the way.

paulspencer 26th August 2005 02:29 PM

If it doesn't need to be connected, then why is it included?

Centauri 26th August 2005 03:06 PM

The 2851 is a very common general-purpose transformer which can be used for a variety of applications, and normally has this centre tap. In the case of this project, they only needed a single 12.6V supply, so the centre tap wire is ignored. I am surprised though, that a spare isolated pad was not provided on the board, or at least mention of the wire in the text.

As Quasi says, just insulate and ignore it.

Cheers
Graeme

paulspencer 27th August 2005 12:36 AM

So the centre tap is there so that you have different voltage options?

UPDATE: I'm now going to add a key switch, so I can disable the whole audio system with a key! :)

Only thing is, the key switches don't handle much power, so I'm going to use a relay with the key switch controlling the power to the coil.

This is a nice feature to have in a diy system, since I can disable it if I'm working on something, so no one can turn it on! I've now made it user friendly enough that others actually CAN operate it now!

Wombat2 27th August 2005 02:12 AM

I have a power supply with a key switch I won't be using you are welcome to. I purchased a new 24 volt PSU off eBay and will be taking it out of the enclosure to use in an amp.

paulspencer 27th August 2005 02:25 AM

Thanks for the offer Wombat, but I've just bought the relay to make it work (after 2 trips to Jaycar, the first time got the wrong relay! :smash: )

paulspencer 27th August 2005 01:16 PM

That project was supposed to take 4 hours, but it has taken me WAYYYYYY longer! I'm still not finished, but it's amazing how quickly the box gets crowded with the extra switch and relay :smash:

Hopefully tomorrow I'll have it working ...

paulspencer 29th August 2005 03:38 AM

FINISHED! ... and working well. With the press of "macro +1 or +2" on my remote it all turns on in 5 seconds, off in 8 seconds.

Now to get my remote volume control going ...


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