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What's relay delay for?

sam

Member
Joined
Jan 17, 2020
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#1
In some teardowns by Amir or in external sites, I have seen lots of relays used as time delay purposes.
They are all used for the AC power input, but I'm not sure what this is for.
Is it something like the soft start feature of some DCDC converters?
 

PaulD

Active Member
Joined
Jul 22, 2018
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#2
There are a number of uses for relays, a non-exhaustive list is:
- To short the output of a signal device until it has powered up properly
- Signal switching and routing
- To switch resistors in/out of circuit for volume control
- Speaker or headphone protection
 

kn0ppers

Active Member
Joined
Jul 4, 2019
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#3
What you will also find sometimes are inrush current limiting resistors or NTCs on power supplies that are bypassed by a relay once the DC supply rails have ramped up.

The most common use of a delay relay seen here is (from my observation) what PaulD mentioned, headphone/Speaker protection purposes. Depending on the design, it might be a simple delay or delay combined with a fault detection (most times DC-Offset) circuit.
 
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