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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


    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,
  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.

    | |
    | |_
    1N4003 - )|
    ^ )| door strike
    | _)|
    | |
    100_Ohm |/
    3.3V-----|___|-----| TIP41
    (created by AACircuit v1.28 beta 10/06/04

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

    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
  5. Joe Webster was thinking very hard :
    Sorry that link is
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