Relays, How to connect

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

  1. jsp2242

    jsp2242 Thread Starter New Member

    Joined:
    Apr 22, 2007
    Messages:
    1
    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

    Joined:
    Jun 30, 2006
    Messages:
    833
    Explain more about what you're trying to do.
  3. Tube Tech

    Tube Tech Active Member

    Joined:
    Jan 11, 2007
    Messages:
    46
    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

    http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/relay.jpg

    Typical relay:

    http://www.bcae1.com/images/jpegs/relaycov.jpg

    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:

    http://www.bcae1.com/relays.htm
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