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14 & 8 volt dc supply from 18 volt transformer..

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yusuf

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Hello all friends !

I have 18volt transformer.
And I have two separate circuit which is:
1)12 volt relay driver circuit.
2)8volt timer circuit.

I want to give separate dc supply to both of them from my 18volt transformer..

Which is I want 14 volt dc for my relay driver circuit to drive properly my relay.
And second I want 8 volt dc supply for my timer circuit to work properly.

Kindly help. because I am new in electronic field..

Thanks.
:)
 
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Is the 18v coming out of the transformer via two wires (the winding) of the transformer? Or are there components such as diodes and electrolytics connected to the winding.
 
I have only 18v transformer and it only contains two wires at primary and secondary..
and nothing else is connected to it...
I have bought this new transformer from market..

And thanks for your reply !
:)
 
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**broken link removed**


You need a set of diodes, an electrolytic and 2 regulators. You can use either a 12v regulator and jack-up the output voltage or a 5v regulator and jack up the output voltage to 14.
Then connect a 5v regulator to the output of the 14v regulator and jack up a 5v regulator to produce 8v. . . . . .
 
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I want 300ma current. in both 14v and 8v supply !

And kindly give me the complete circuit..
And I want to use 18volt transformer so how should I do it...
 
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You lost me a little here:

I have 18volt transformer.
And I have two separate circuit which is:
1)12 volt relay driver circuit.
2)8volt timer circuit.

I want to give separate dc supply to both of them from my 18volt transformer..

Which is I want 14 volt dc for my relay driver circuit to drive properly my relay.
And second I want 8 volt dc supply for my timer circuit to work properly.

If the relay circuit is 12 volts why the 14 volts? I would think 12 volts for a 12 volt relay circuit. What am I missing?

Ron
 
Firstly you wanted 100mA per output, now you change it to 300mA.
Take the regulators from the 25v DC output of the bridge.
 
If the relay circuit is 12 volts why the 14 volts? I would think 12 volts for a 12 volt relay circuit. What am I missing?
We should give always little high voltage to relay because sometimes it stuck or jams ... and it can't switch properly..

So by giving a little more voltage it work great without jamming or stuck !

So I have used 14 volt here ..
we can also select 13 volt...
 
ake the regulators from the 25v DC output of the bridge.

Hi colin thanks for you reply...

But as you know I am newbie in electronic ... so if possible can you give me a complete circuit which suit my needs...
Because I understand better from circuit rather then theory ..
 
Yusuf, good relays work just fine at their rated coil voltages and actually have a pull in rating below their rated coil voltage and a drop out voltage specification for their coil. I guess if you want to run 12 volt relays at 14 volts it's your design but I do not see it as a good design practice for someone starting out and learning. While most relay coils are forgiving I do not see it as a good practice to design in over voltage for a relay coil. Something else to consider is the relay coil has resistance so for a given voltage it will draw a given current to operate correctly. Since the coil resistance is a fixed value if we increase coil voltage the coil current will increase proportionately so we use more current. Automotive relays are a good example of relays with a coil designed for a wide voltage range but for other relays this is not good practice. If a relay gets stuck or jammed it is likely because the wrong relay was chosen for an application.

Just My Take
Ron
 
Thanks Reloadron !
:)
I hope you have good excellent knowledge of electronic..

So can you also help me in my new thread which I have posted .... it is upon bistable !

Thanks again !
 
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