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Topic Title: Mains Present LED Before or After Fuses
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Created On: 23 May 2013 09:42 AM
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 23 May 2013 09:42 AM
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I'm trying to decide whether a "mains power present" indicator LED in a PSU circuit should be placed before or after the fuse. There are arguments for both configurations:

1) LED after fuse - Fuse blows and LED extinguishes but mains power is still present at the input of the PSU creating electrocution risk
2) LED before the fuse - Fuse blows and LED remains illuminated reducing electrocution risk. However, this creates a potential fire hazard.

Preferred solution for the application is LED after fuse but I'm wondering if anyone knows if there are any standards out there that govern how this should be done.
 03 September 2013 04:26 AM
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Fast fuse and slow fuse.
Fast fuse with slow fuse the main difference is that its capacity of instantaneous pulse current
Slow fuse can resist the impact of the switch machine surge current without action, so as to ensure the normal operation of equipment, so slow fuse is often also called surge resistant fuse.
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 05 September 2013 02:38 PM
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Go for both. Use a mains indicating neon/LED rocker switch (Mains supply present) and an LED to indicate psu/control output voltage present/healthy.

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