Relays, How to connect

Discussion in 'General Electronics Chat' started by jsp2242, Apr 22, 2007.

  1. jsp2242

    jsp2242 Thread Starter New Member

    Apr 22, 2007
    I have a need to install a power relay in a circut with a ext. fuse box at the end. I have several Bosch relays of the correct amp rating but i'm confused with what to do with the switch lead on the 4 post relay, same with the 5 post. what swithch (Type) would I connect it to?-JSP2242
  2. mrmeval

    mrmeval Distinguished Member

    Jun 30, 2006
    Explain more about what you're trying to do.
  3. Tube Tech

    Tube Tech Active Member

    Jan 11, 2007
    Pin numbers are not standardized among relay manufacturers. 5 pin tells us nothing.

    Bosch relays don't have a 4 or 5 pin. Google Bosch relays under images tb, you find the images below

    Typical relay:

    5 and 6 in the images of the typical relay perform the same function as 30 on the Bosch relay. It's the common contact.

    The typical relay is a DPDT switch. Pin 5 normally connects to pin 1, NC, normally closed. When the coil is energized, that contact opens and common connects to pin 3, the NO, normally open contact.

    So: on this typical relay, A and B are the coil. 5 and 6 are the common contacts for the 2 switches. 1 and 2 are normally closed, they are connected to common when the relay is relaxed. 3 and 4 are normally open, connected the common contact when the relay is energized.

    You could just read the tutorial:
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