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Karu  
#1 Posted : Monday, August 17, 2009 7:05:52 AM(UTC)
Karu

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Hi,

How many VA's the 7V transformer needs to be to drive 2*Volumite, 2*controller, and 2*Joshua Tree?
Karu  
#2 Posted : Tuesday, August 18, 2009 6:53:19 AM(UTC)
Karu

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Since LM7805CT is rated for 1A, am I correct to calculate:

Dropout Voltage = 2V
min. Voltage in = 5V + 2V = 7V
Minimal dropout current

2KBP01M Bridge Rectifier:

Forward Voltage @ 1A = <1V
min. Voltage in = 7V + 1V = 8V
Minimal dropout current

Transformer:
min. Voltage Out = 8V/sqrt(2) = 5.7V

So, at minimum 6V 1A transformer can power one of everything.
For the whole set 15VA 2*7V should be safe and enough?
Russ White  
#3 Posted : Tuesday, August 18, 2009 3:20:41 PM(UTC)
Russ White

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I would think that should work fine.

But you might want to go slightly larger if you have the space just to be safe.
Karu  
#4 Posted : Thursday, August 20, 2009 5:59:42 AM(UTC)
Karu

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Thanks!

I'm currently planning to use 30VA 9V toroid. PSU will produce 5V 3A to power the units.
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