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Old 11-01-2008, 11:50 PM   #16
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Connecting AC to a DC device


VA isn't quite watts, but you might as well consider it watts in a situation like this. VA=watts for DC or when the load is pure resistance (or the power factor is perfect) for AC. Anyway not to get too complicated, yes VA is basically watts.

If the power supply isn't getting too hot, you are probably ok.

The 4amps is just a surge when it first starts up right? The camera only normally pulls around 1.2 amps you said. Also the PTZ probably won't pull much power when it's not actually moving.

Since you have an ammeter you can measure the actual amps each pulls when running, panning, etc. It might be ok and it might not, but remember the heat dissipation capability of the wires and the power supply are the limiting factor here, if nothing is getting hot (and the voltage isn't dropping too low) then you are OK.

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Old 11-02-2008, 01:13 AM   #17
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Connecting AC to a DC device


Gigs,
Yes the camera only pulls around 1.2 amps when it is idling, however the 4 amps is what I measured when the camera was panning and scanning at the same time. I believe it pulled somewhere between 2.5 to 3.5 amps when it was only doing one type of movement. I am willing to try connecting both devices to a single power supply and feel to see if anything starts getting hot, but I don't really have any method of initiating the heater in the enclosure while everything else is connected. Thus, I would have to actually wait for it to get cold enough outside before I would know whether such a connection would be safe to use.
Because of this, I would feel better if I had a higher amperage power supply, assuming that would solve the problem. Which is another thing I wanted to ask. If I used a single 24VAC 100VA transformer, all this means is that this transformer is able to supply more current if necessary, meaning it would be a safer method of powering both devices?
Or another idea, if I wired the two power supplies together in parallel, would this sum the amperage of the two power supplies?
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Old 11-02-2008, 01:41 AM   #18
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Connecting AC to a DC device


It's good to be conservative and give yourself a little headroom. The items will only use the amps they need.

Putting two transformers in parallel raises new issues. If they are not the exact same rating, one will bear more load than the other, get hotter, and possibly trigger what's called a cascade failure, where the failure of one causes the failure of both. I would not do it. The same can happen with DC power supplies in parallel.

It is safe to use a single larger transformer or power supply to power both. Whether that saves you money or not you'll have to figure out. It is good that you are carefully considering this before rushing forward.
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Old 11-02-2008, 09:11 AM   #19
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Connecting AC to a DC device


Quote:
Originally Posted by kimbokasteniv View Post
And Yoyizit, you were saying that such power supplies are short circuit proof.
Some might be but doorbell xformers are.

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