Need help building a 110v/240v automatic switcher.

Thread Starter

born2dive00

Joined Oct 24, 2016
285
Hello everyone I need help building an automatic switcher that can handle 10A@ 110v, 5A@ 240v.
I have a need to be able to connect 1 cord to a wall outlet that can be either 110v or 240v and to switch a relay tripping a 110v/240v switch on a 12v power source. Let me explain more I have a power inverter 12.5A/dc on the inverter there is a switch for using 110v or 220v. I have replaced the switch with a 240v relay so that when 240v power is introduced it energizes the relay and connects the NO contacts for 240v. when the coil is off it is connected to the NC contacts with 110v.

My concern is that with the contacts closed in the 110v position, when I apply 240v to switch on the coil and close the contacts to the 240v position, that, that millisecond of 240 applied to the 110 contacts will burn out the components of this ac/dc inverter.

Do I need to worry about it, or should I have some sort of high low voltage automatic switcher??? how would I design this.

Please let me know
 

MrChips

Joined Oct 2, 2009
22,099
I like the idea of using a 240VAC relay on the power line.
Now install a manual power switch on the input of the transformer windings.

Post a clear warning that the power switch must be OFF before plugging into power outlet.
 

MrChips

Joined Oct 2, 2009
22,099
What and where are you going to plug the same device into either a 120 or 240 wall outlet?

Ken
Presumably this is a product for the international market. The receptacle on the unit could be the same. The power cord could change depending on the country of destination. That's my guess.
 

Hypatia's Protege

Joined Mar 1, 2015
3,226
Hello everyone I need help building an automatic switcher that can handle 10A@ 110v, 5A@ 240v.
I have a need to be able to connect 1 cord to a wall outlet that can be either 110v or 240v and to switch a relay tripping a 110v/240v switch on a 12v power source. Let me explain more I have a power inverter 12.5A/dc on the inverter there is a switch for using 110v or 220v. I have replaced the switch with a 240v relay so that when 240v power is introduced it energizes the relay and connects the NO contacts for 240v. when the coil is off it is connected to the NC contacts with 110v.

My concern is that with the contacts closed in the 110v position, when I apply 240v to switch on the coil and close the contacts to the 240v position, that, that millisecond of 240 applied to the 110 contacts will burn out the components of this ac/dc inverter.

Do I need to worry about it, or should I have some sort of high low voltage automatic switcher??? how would I design this.

Please let me know
Please be advised that proper/safe/sane design will obviate liability to supply contention via (exclusive) selection of the power source - as opposed to the load!:rolleyes:

Best regards and take care!
HP:)
 

AlbertHall

Joined Jun 4, 2014
10,558
I like the idea of using a 240VAC relay on the power line.
Now install a manual power switch on the input of the transformer windings.

Post a clear warning that the power switch must be OFF before plugging into power outlet.
You might as well use the original manual voltage change switch.
 

AlbertHall

Joined Jun 4, 2014
10,558
If you want to make this automatic switch then you need another relay which only connects the power after a delay to allow the voltage selector relay to have fully operated. But I don't like it - see post #5.
 

Thread Starter

born2dive00

Joined Oct 24, 2016
285
Presumably this is a product for the international market. The receptacle on the unit could be the same. The power cord could change depending on the country of destination. That's my guess.
MrChips, this is exactly right, I use this ac/dc power supply when I am in the states, and when I am working international. Ergo the need for 110 and 220v going to the same wire to the same power, just have to remember to flip the switch which I have not done all the time and have on occation sent 220 thru the 110 circuit and Puff. this is the reason I want a automatic switcher.
 

Thread Starter

born2dive00

Joined Oct 24, 2016
285
If you want to make this automatic switch then you need another relay which only connects the power after a delay to allow the voltage selector relay to have fully operated. But I don't like it - see post #5.
Thank you Albert Hall, I understand the concern and warning this is why I need to do this safely, If you think of your computer and most chargers for phones, they already do this automatically, but can not handle the 10 amps dc I need. So having that said, how do I get the delay that you spoke of?? contact out put from the 240 on relay one into the coil and NO contact of relay 2?
 
Is there any way to do this with out relays like on a computer charger? but with 10A DC out?
AFAIK most chargers use 'ORing' techniques -- which being FAIAP inapplicable to AC...

If you actually wish to switch DC in said manner -- you may merely use diodes (rectifiers) possessed of the requisite If specification -- howbeit such seems inconsistent with your OP?:confused:
Best regards
HP:)
 

crutschow

Joined Mar 14, 2008
25,664
Change the relay operation so that the NC (relay unenergized) connects the 220V circuit and the NO contact (relay energized) the 110V.
That way the momentary connection before the relay changes state is 110V applied to the 220V connection which should do no harm.
 
Change the relay operation so that the NC (relay unenergized) connects the 220V circuit and the NO contact (relay energized) the 110V.
That way the momentary connection before the relay changes state is 110V applied to the 220V connection which should do no harm.
But the inverter is not synchronized to the line:eek::eek::eek: -- Perhaps I'm misinterpreting the OP?:confused:...

Best regards
HP
 

crutschow

Joined Mar 14, 2008
25,664
But the inverter is not synchronized to the line:eek::eek::eek: -- Perhaps I'm misinterpreting the OP?
I believe you are.
His concern seems to be that 220V will be momentarily applied to the 110V input during the delay of the relay switching (below).
That's why I suggested reversing the process so the unenergized position of the relay is to connect the 220V input instead of the 110V input.
My concern is that with the contacts closed in the 110v position, when I apply 240v to switch on the coil and close the contacts to the 240v position, that, that millisecond of 240 applied to the 110 contacts will burn out the components of this ac/dc inverter.
 

Thread Starter

born2dive00

Joined Oct 24, 2016
285
Change the relay operation so that the NC (relay unenergized) connects the 220V circuit and the NO contact (relay energized) the 110V.
That way the momentary connection before the relay changes state is 110V applied to the 220V connection which should do no harm.
I like that idea and thought about that BUT there needs to be 1 cable in and one cable out, that handles both 110v and 220v. Thus if I run the power from the cable to the relay, the coil will either have 110v or 220v then I jump it from the coil to the contacts.
 

Thread Starter

born2dive00

Joined Oct 24, 2016
285
Is there any circuit that can be built to do this, 110v out turns energizes a relay coil, and 240 does not energize a relay coil.
Remember that the unit must have only one cable in using both 220v and 110v, to the circuit turning on a relay coil with 110v, and keeping the relay off with 220vUntitled.png
Is there any way to make this circuit as described? I could us a 110v relay then connecting the 220v to the NC but would need to prevent 220v going to the relay coil to prevent switching.
 

AlbertHall

Joined Jun 4, 2014
10,558
Change the relay operation so that the NC (relay unenergized) connects the 220V circuit and the NO contact (relay energized) the 110V.
That way the momentary connection before the relay changes state is 110V applied to the 220V connection which should do no harm.
But then you need some way of getting the relay to operate when 110V is applied but to not operate when 220V is applied.
 

Thread Starter

born2dive00

Joined Oct 24, 2016
285
But then you need some way of getting the relay to operate when 110V is applied but to not operate when 220V is applied.
Albert hall, what were you thinking?? I am not really following you. I agree with 220 connected to the NC position, if I am running both 110/240 thru one cord, the coil would be energized if I applied 110v to energize the coil to trip the NO circuit, but when the 240v hits the coil if it is a 110v coil it will burn out would it not?

Unless there is a 110v-220v coiled relay that I am not finding, then this would also work. 220 NC, 110 NO, and tripping the coil with either 110or 240v.

IS there a relay with a coil that can handle 110-220v AC??
 
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