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Relay Use Rule Of Thumb

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danner123

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Hey everyone, I have a real basic question. I am using a SPST (single pole single throw) relay on my test fixture. I have 1.5V as the COM line. I want to switch this 1.5V to the NC (Normally closed) or NO (Normally Open) lines out. Basically I have just using the relay to switch the 1.5V supply to two different lines.

My question is: Is there a rule of thumb on whether to enable the 1.5V supply first and then switch in the relay (actuate relay) or switch in the relay and then enable the 1.5V supply? Or does it even matter the order? Would the relay have a longer time adjusting to the voltage on the line if the 1.5V supply was enabled at first and then the switch was switched in?

The same goes for shutting down the relay that is actuated. Would I first turn the supply off and then unactuate the relay? Or does it not matter? Will the relay be ok if I unactuated it while the supply was still on?


What is the rule of thumb for relay use in this aspect?



Thanks!
 

danner123 said:
Hey everyone, I have a real basic question. I am using a SPST (single pole single throw) relay on my test fixture. I have 1.5V as the COM line. I want to switch this 1.5V to the NC (Normally closed) or NO (Normally Open) lines out. Basically I have just using the relay to switch the 1.5V supply to two different lines.

My question is: Is there a rule of thumb on whether to enable the 1.5V supply first and then switch in the relay (actuate relay) or switch in the relay and then enable the 1.5V supply? Or does it even matter the order? Would the relay have a longer time adjusting to the voltage on the line if the 1.5V supply was enabled at first and then the switch was switched in?

The same goes for shutting down the relay that is actuated. Would I first turn the supply off and then unactuate the relay? Or does it not matter? Will the relay be ok if I unactuated it while the supply was still on?


What is the rule of thumb for relay use in this aspect?



Thanks!
Click to expand...

I guess the problem is elsewhere- in the load to which the relay connects (or disconnects) the 1.5 V source.
If the load should be cut off the source by the relay, then the relay contacts will do it (on or off) without any respect to what happens at source terminals. Imagine a 1.5 V battery as the source.

If the load requires the full 1.5 V to be connected to it by relay contacts when driven to on, then keep the source operating.

This is a typical logic AND operation: switching ON the DC source, plus switching ON the same source, now to the load.

You can avoid the second pair of contacts by simply using the relay to power ON the source.
 
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