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What is a latching relay vers a non latching relay

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by MrDEB, Apr 22, 2007.

  1. MrDEB

    MrDEB Active Member

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    Looking for a simple DPDT 12vdc coil relay. Contacts to carry 24 v dc to control a solenoid.
     
  2. Leftyretro

    Leftyretro New Member

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    A latching relay has internal magnet(s) that will hold the relay once energized so that power to the relay only has to pulse it on or off, thereby saving energy by not requiring that the coil be continuously powered. Some latching relays have two coils, one for setting and one for resetting, some only have one coil and rely on power polarity reversals to set and reset the relay.

    Sounds like you only require a standard non-latching relay which is by far the more common flavor :) Be sure to find out the current requirments for your solenoid so that you can make sure the relay contacts are rated for that amount or higher.

    Lefty
     
  3. aaatif

    aaatif New Member

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    Latching relay control through Microcontroller

    Hi all

    I need some help related to the latching relay...

    I am using 5VDC single coil latching relay TN-L-5V...I have to control it using a single line of microcontroller...but it needs two pins for set and reset (As mentioned in the above reply; polarity reversal for set/reset)

    I have to control 20 relays on the PCB, of the size 4x4 inches. If i use a simple inverter for polarity reversal, my PCB size cannot accomodate 4 ICs plus 20 relays.


    Is there any other option than Inverter?
     
  4. dave

    Dave New Member

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  5. aaatif

    aaatif New Member

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    another problem, which i forgot to mention is, micro controller cannot supply sufficient current to relay. Use of transistor also makes it impossible to develop PCB of size 4x4
     
  6. erosennin

    erosennin New Member

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    How about you make a double sided board?
    Micro + Transistors on one side, relays on the other. I realise if you are going to make this manually at home, vias could be an issue - you can just use hook up wire :rolleyes:
     
  7. aaatif

    aaatif New Member

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    Use of transistors is never suitalbe. I told earlier that i am using 20 relays. If i use transistors, for each relay, i will have to use two, and for 20 relays, 40 transistors will be required. :(

    vias may not be the problem. Space is the biggest issue.
     
  8. erosennin

    erosennin New Member

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    Is your micro able to sink the current required, rather than source it? That may solve your problem if it is able to. Remember you need diodes as well =P
     
  9. Helder Ferreira

    Helder Ferreira New Member

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    Pic type microcontrollers from Microchip can source/sink 20 mA per pin (not all at the same time) that is >= 250ohm relay coil. If you common one connection of all the relays and if you don't have to switch more than one relay at a time, you could take advantage of the tri-state condition of the pins. With couple of transistors, you connect the "relay common" connection to + or - and switch the micro's pin from high impedance to high or low, depending on the operation required.
     
    Last edited: Nov 22, 2007

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