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I'm considering to use the Omron G5V-1 Relay in order manage a 5 VDC 1.5 A charge. Reading the datasheet I did not completly understood what is the Relay maximum supported current, considering that I'm working at 5 VDC.

What's the difference between Rated Carry Current and Max Switching Current? Which of these two should I consider as the current limit?


In the last page of the datasheet I found this paragraph:

Long-term Continuously ON Contacts

Using the Relay in a circuit where the Relay will be ON continuously for long periods (without switching) can lead to unstable contacts, because the heat generated by the coil itself will affect the insulation, causing a film to develop on the contact surfaces. Be sure to use a fail-safe circuit design that provides protection against contact failure or coil burnout.

What Long-term means? Are we talking about hours, days or what?

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What's the difference between Rated Carry Current and Max Switching Current? Which of these two should I consider as the current limit?

The rated carry current is always the higher figure - basically if you switch a relay on/off at its maximum carry current then you are doing the contacts harm - you should only switch at the max switching current. If that current then grows to the rated carry current that is fine but, before switching the relay off the current has to fall-back to the max switching current.

It won't instantly "fail" if you don't follow the rules but its life will be impaired and it will eventually fail sooner because of this.

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    \$\begingroup\$ Thank you, you answer is very clear. What about the Long-term Continuosly ON Contacts? \$\endgroup\$
    – Oceanic815
    Oct 20 '13 at 22:50
  • \$\begingroup\$ @Oceanic815 contacts tend only to degrade when opening and closing but of course relays are mechanical items and you have to check the data sheet to see how many on-off operations they are rated for - it's usually in the millions. \$\endgroup\$
    – Andy aka
    Oct 21 '13 at 7:08

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