Relays

Discussion in 'General Electronics Chat' started by kibble0, Jul 18, 2011.

  1. kibble0

    Thread Starter New Member

    Jul 18, 2011
    5
    0
    Hi all
    quite new to the world of electronics and been mucking about with for a few months now i have a basic idea i would like to try out and was wondering if i could get help here.

    what im tyring to do is make a Humidity sensor using a arduino and a wireless on/off plug for the mains power
    i have wired up the remote and all i need this system to do is just make the connection for the remote to send its signal to the plug to turn on or off.

    i got my self a couple of 5v relays and tired this and it didnt work i have seen something called a reed relay but i wondering if im going down the right road with this. from what it looked like to me a reed relay works when the power is on the brakes the connection is this right?

    sorry for lack of knowledge of this

    thanks for your time


    Dave
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Your wireless remote probably does not supply enough current to cause the relay coil to energize.

    It's going to be difficult to make progress until you can supply us with details for the remote, preferably a datasheet, at a minimum the manufacturer and part number, and the same kind of information for your relays.
     
  3. kibble0

    Thread Starter New Member

    Jul 18, 2011
    5
    0
    thanks for reply back so quickly

    as for data sheets i dont have any and as for the relays i dont have the info to hand as for the remote.

    i got from a diy shop that comes with 3 plugs and using the remote can turn them off the remote has its own battery power which is grand all i have done is taken the on button and off button and soldered on some cable all they have to do is connect and the remote dose the rest.

    tho i havent programed the script yet was going to use the 5v on the arduino to get the relay to turn on and make the connection for the remote. and it only has to be on for a max of 1 second. thats the plan. from what i get the relay i have got i think its this one but will check when i get back.

    http://www.maplin.co.uk/2a-dpdt-bt-type-47-equivalent-relay-37522?ordercode=N18AW

    this uses to much power and my best bet would be a reed relay tho dont know which one.

    tho saying this im not 100% on that


    cheers

    Dave
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Reed relays are usually VERY low current and for low voltage only. If you want to control mains power, the relay must be rated for the voltage and current that will be switched, and you should use a fuse in series with the contacts that is rated for less current than the contacts - but the same or higher voltage.
     
  5. kibble0

    Thread Starter New Member

    Jul 18, 2011
    5
    0
    ok cool im staying away from mains power at the moment that is the reason for the remote on/off set

    this not the same as what i got tho the idea is same
    http://reviews.dealsdirect.com.au/0553/37405/reviews.htm

    2 reasons im using this saves me being electcuted and as its wireless so i can putt everything in a small box
     
  6. Metallica_Boy

    Member

    Nov 8, 2006
    10
    1
    you can make a transistor as a switch circuit before the relay

    Using a transistor as a switch
    When a transistor is used as a switch it must be either OFF or fully ON. In the fully ON state the voltage VCE across the transistor is almost zero and the transistor is said to be saturated because it cannot pass any more collector current Ic. The output device switched by the transistor is usually called the 'load'.
    The power developed in a switching transistor is very small:

    In the OFF state: power = Ic × VCE, but Ic = 0, so the power is zero.
    In the full ON state: power = Ic × VCE, but VCE = 0 (almost), so the power is very small.

    http://www.kpsec.freeuk.com/trancirc.htm
     
  7. kibble0

    Thread Starter New Member

    Jul 18, 2011
    5
    0
    cool i will look into this

    as for the relay i found its a LU-5

    and after finding it online and finding a digram i got it working its now working with the arduino which is class.

    was looking at a relay from a book and was thinking it was the same layout thus it didnt work.
     
  8. kibble0

    Thread Starter New Member

    Jul 18, 2011
    5
    0
    and thanks for the link thats really useful :)
     
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