# Using a relay to switch voltage in a circuit

#### USBthree21

Apr 5, 2022
3
Hi everyone, I am planning a circuit that is normally 32v DC but would switch to a 12v battery (equipment works fine on both, and is made to recognize and run at slower speed when on a 12v power source (to save battery).

The power source are 2 mean well PSU (MDR-40-5 and NDR-120-24) in series and voltage adjusted to achieve 32v DC total between the two. To achieve the switch I would use a relay (Omron LY2N-D2 DC24) which is a 2 form C (DPDT) relay, with a 24 vdc coil (powered by the 24v PSU), when power goes down, it would swap to the 12v battery.

Normally I always connect the power source to the 5 or 6 pole (wiring picture of the actual relay attached) and then the actuator side would be on poles 1,2,3 or 4. Would it be a problem to connect the PSU on poles 1 and 2, and the battery on 3 and 4, while having the pump (in this case) on the 5 and 6 poles? This way I should be able to switch both polarity cables from one source to another, but I am worried somehow the voltage differential of those very close contacts be an issue. What do you guys think?

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#### WHONOES

May 20, 2017
1,215
Please give us a diagram of what you propose.

#### USBthree21

Apr 5, 2022
3
Here it is, normally you would put a diode between the 2 PSUs in series (in case one turns on before the other), but these ones already have it in the internal circuitry. Also, they are both 5A so they won't overpower each other.

#### Attachments

• Screen Shot 2022-04-06 at 10.54.35.png
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#### USBthree21

Apr 5, 2022
3
Sorry, my mistake, the second PSU (on the right), says voltage regulated at 26v, but that was supposed to say voltage regulated at 6v.

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