Power supply determination?

SeanC

Joined Feb 7, 2017
3
I have a desktop fish tank that has a filter and led light that uses same wall wart that has 2 wires coming from it. My question is what voltage and amperage do I need for a wall wart just for light separate so I can plug into a timer seperate. The easy way to do this is the filter says it's 12v 3w so if my math right it's drawing 250ma. What confuses me is the wall wart states output: 12Vac 600ma 7.2Va . So the 7.2Va is throwing me off what does it mean/isn't circuit 12v? Also the light is a total of 24leds but has a switch to run 21 white or 3 blue for night light. I will provide pictures and need to know what voltage and amperage wall wart is needed/safe. I have a wall wart with same connector/plug as light wire but it's 9Vac 200ma will it work? I know being 9v it will be dimmer but is amperage safe? Please help need this light on a cycle for my plants asap Thank you

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wayneh

Joined Sep 9, 2010
17,153
12VAC x 0.6A = 7.2VA = 7.2W For this discussion, watts and volt-amps are the same. Don't worry about it.

The 9V wall wart might light the LEDs but probably not. LEDs require a minimum voltage and if they work at 12V, they probably won't work at 9V. They might. More importantly, your 9V wall wart is only rated to 1.8W. It will be severely overloaded with the LEDs, or the filter, or with either. Unless you know the filter or the LEDs use well under 1.8W, don't use that adapter.

Don't worry about an amperage rating above what you need. That's just extra capacity that will go unused, and is a good thing. So for instance if you have two wall warts with the same 7.2W rating, that would be fine. You'd have no worry that either will get overloaded.

SeanC

Joined Feb 7, 2017
3
12VAC x 0.6A = 7.2VA = 7.2W For this discussion, watts and volt-amps are the same. Don't worry about it.

The 9V wall wart might light the LEDs but probably not. LEDs require a minimum voltage and if they work at 12V, they probably won't work at 9V. They might. More importantly, your 9V wall wart is only rated to 1.8W. It will be severely overloaded with the LEDs, or the filter, or with either. Unless you know the filter or the LEDs use well under 1.8W, don't use that adapter.

Don't worry about an amperage rating above what you need. That's just extra capacity that will go unused, and is a good thing. So for instance if you have two wall warts with the same 7.2W rating, that would be fine. You'd have no worry that either will get overloaded.