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DC Relay

Discussion in 'Electronic Basics' started by Joe Webster, Mar 10, 2005.

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  1. Joe Webster

    Joe Webster Guest

    Hello,

    I'm just a complete novice when it comes to building circuitry. The
    current project I'm working on involves a electronic door strike. The strike
    requires at least 6vdc to unlock, I'm not sure how many amps right now and I
    don't have it with me. Given things I can't change, when the door is to be
    opened I'll have 3.3vdc to trigger the lock. My first thought was just to
    get a simple relay that will switch the 6vdc when I supply 3.3vdc to the
    coil of the relay.

    So I need a relay w/ a nominal voltage of 6vdc w/ a minimum coil voltage
    of 3.3vdc. Searching online at RadioHack and Mouser, this seems easier said
    than found. I've found some that come close. RadioShack part# 275-232 which
    has a min. switching voltage of 3.5vdc.Same goes for mouser.

    So my question is "is there a better way to solve my problem" -- or
    "could I somehow step up the 3.3v to say 6v and maintain that for at least
    5-10 seconds?"

    Thanks everyone,
    Joe
     
  2. It's a bit hard to understand what you are asking but if I have it right,
    you want a relay with a coil that operates on 3.3vdc to switch a 6vdc supply
    to the door strike ?
    Is the "min switching voltage" of the relays mentioned the actual voltage
    required for the coil ? since a "min switching voltage" sounds a little
    strange to me.
    I would be inclined to try one, and mebbe increase the supply volts for the
    strike too :)
     
  3. Sounds you have a 6V power supply already and I assume it to be powerfull
    enough to activate the door strike. All you need is a resistor, a transistor
    and a diode. The transistor needs to be able to handle the current the door
    strike needs. Use a TIP41 for instance.

    +---+--------6V
    | |
    | |_
    1N4003 - )|
    ^ )| door strike
    | _)|
    | |
    +-+-+
    |
    100_Ohm |/
    3.3V-----|___|-----| TIP41
    |>
    |
    |
    |
    -----------------+-----------
    (created by AACircuit v1.28 beta 10/06/04 www.tech-chat.de)


    petrus bitbyter
     
  4. Chris

    Chris Guest

    Hi, Joe. Not quite enough information to work on, but I'm going to
    assume you're working with a 3.3V logic signal. 3V relays are made,
    but they usually require more current to drive the coil than a logic
    signal can provide, and they're not that common. Also assuming the
    3.3VDC control signal and the 6VDC-plus power source have the same
    common, it might be better to use a transistor to turn the lock
    solenoid on and off (view in fixed font or M$ Notepad):


    6VDC Plus
    o------------o--.
    1N5402| | Solenoid
    - C|
    ^ C|
    | C|
    | |
    3.3VDC '--o
    Control Signal |
    (1 = ON) ___ |/
    o-----|___|-o-| TIP120
    4.7K | |>
    .-. |
    | | |
    4.7K| | |
    '-' |
    GND | |
    o-----------o---'
    created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

    You can get the specified darlington transistor as well as the diode
    and the rest at Radio Shack or Mouser. This circuit is good for
    switching up to 1 amp, and 3 amps with a heat sink on the transistor.
    If you need to switch up to 6 amps, you'll have to replace the diode
    with a 6 amp diode.

    Good luck
    Chris
     
  5. Joe Webster was thinking very hard :
    Sorry that link is www.adilink.com
     
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