Hi, Can anyone help me? I am building a machine at the moment and I am stuck on a bit of it. I need a switch that I can use to reverse the mains input. I don't want anything too huge and heavy duty but I am aware that a simple rocker switch wouldn't work as I need a clean break in the middle to prevent sparking etc. Any ideas are welcome - perhaps using relays / logic etc. Cheers Jo
Let me know if this isn't clear I'm not very good an explaining things!
Why? What do you hope to achieve? It is hard to answer questions without knowing the problem. Wot's Your Real Problem?
Voltage, amperage?
A 4way switch will do what you want, if you your needs are modest.
Basically I have 2 lines coming into the machine one Live and one Neutral (mains voltage) and i want to be able to reverse the input so that the live wire carries neutral and vice versa. I have found a machine with a switch that does the job and in the instructions it says "A heavy-duty rotary switch with a centre off position which enables the live and neutral connections to the power socket to be reversed. The switch has a mechanical interlock which ensures that the lever movement must pause at the centre position, open circuit" Unfortunately this appears to have been specially made I can't find anything similar to buy. Hope this is clearer Jo
You have not explianed why you would want to do this inherantly UNSAFE action nor what sort of load you want to switch.
I'm still a bit confused as to why you would want to reverse the mains input, as in AC electrics this will not achieve anything other than to confuse people and possibly make it more dangerous. Are you trying to reverse a motor? If so, please post the motor type and I will try my best to help. Regards, PF
This is a safety "no-no" if the user can access the reversed line and neutral at the power socket you mention. If the line and neutral stay within the equipment and are not accessible to the user, that safety concern goes away.
Assuming you do not have a safety issue, you can accomplish what you posted easily. You can get a DPDT center off switch from Allelectronics for $1.50 - CAT# MTS-120PC. That allows reversing polarity and stopping in the center. The switch is rated for 5 amps at 120 volts AC. No matter how rapidly you flip the switch, the circuit will be interrupted before it is reversed. Or did you need a relatively long pause??
Regardless of the length of the pause - 10 microseconds or one hundred years or whatever - you can get sparking any time you interrupt the circuit.
Assuming that a momentary interruption of power is all you need: If you need higher current/voltage, you can look for "beefier" switches, or you can use the switch already mentioned to operate relays which will handle the higher specs. CAT# RLY-427 for $4.00 (you need 2) will handle 35 amps at 277 VAC See
Here's a diagram:
Ry1 Ry2-1 Hot-fuse---C +-------------------A \ | Ry2-2 / A--+---B C----load---C B / | Neutral-------------A---------------+
As drawn, C is the common point in the set of relay contacts, A is the open point, and B is the closed point. A and C connect when the relay is energized, while B and C connect when the relay is not energized.
The switch would be wired so that in one on position it energized both relays, and in the other on position energized only relay 1.
Sw1-1 Hot--+--C A---+---relay 1 coil-----+------Neutral | \ | | | B---+ | | | | Sw1-2 | +--C A-------relay 2 coil-----+ \ B
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