Discuss Can I use this switch button to turn an AC/DC PSU on and off? in the Electrical Forum area at ElectriciansForums.net

multimarcus
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I would like to control a Power supply AC/DC connected to mains with an input of 230v (2.4A/115VAC; 1.2A/230VAC) and output 5v / 40A (200Watts). Can I use a switch button rated 3 A @ 250 V AC to turn it on and off? It would be one of these or something similar.
 
DPG

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I would like to control a Power supply AC/DC connected to mains with an input of 230v (2.4A/115VAC; 1.2A/230VAC) and output 5v / 40A (200Watts). Can I use a switch button rated 3 A @ 250 V AC to turn it on and off? It would be one of these or something similar.

That looks like a momentary switch. You would need a latching one. I haven't checked the voltage/current ratings.
 
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multimarcus
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That looks like a momentary switch. You would need a latching one. I haven't checked the voltage/current ratings.
Thank you! Since it will have to handle up to 40A of current, should I also add a relay between switch and PSU?
 
telectrix

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as above 40A (200watts) @ 5V is roughly 0.8A @240V. allowing for losses in the PSU , 1A is close to the mark. you'll need some fat cables on the 5V side though. 6.0mm?
 
DPG

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The PSU is rated at 1.2A, so you need a switch rated for 230VAC or above and current of around 2A or above.
 
Lucien Nunes

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Don't forget that SMPSUs can have high inrush that can weld switch contacts together. I would look for a switch with at least 3A inductive or 10A resistive load rating to ensure reliability.
 
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multimarcus
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That's ok then, the output current may be 40A, but the input current will not be. Remember, power is I x V and so the higher input voltage means less current.
Thank you! Yes indeed I was a bit confused as to which amount of current I was supposed to look at and provide a switch for. First time working with switches and AC.
 
DPG

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Thank you! Yes indeed I was a bit confused as to which amount of current I was supposed to look at and provide a switch for. First time working with switches and AC.

No problem. Bear in mind Lucien's good advice about choosing a suitable current rating. Your switch will last longer then.
 
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multimarcus
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Don't forget that SMPSUs can have high inrush that can weld switch contacts together. I would look for a switch with at least 3A inductive or 10A resistive load rating to ensure reliability.
Thank you! This is really useful. The PSU will be powering 11 LED matrices, each potentially drawing up to 3A (though it will stay below that as I won't use full white colours)
 

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