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Make Electronics Experiment 8 -Problem

Discussion in 'General Electronics Discussion' started by HelpMe123, May 22, 2019.

  1. HelpMe123


    May 22, 2019
    Hi, I am trying to build the circuit shown below but it doesnt work. The left led is always on, no matter of i push the button or not. On the other Hand the right led is always of. Can you please tell me what I am doing wrong?

    Thanks in advance

    circuit diagram 1:


    circuit diagram 2:


    my circuit:


    [mod edited to put circuits inline]
    Last edited by a moderator: May 23, 2019
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Make them smaller, less than 250 kB usually works well.

    Re your problem: does the relay operate when you press the button?
    - check the connection from the button to the relay coil.
    - check the supply voltage.

    Your relay has a 12 V coil, if you use it with a 9 V battery as diagram #2 suggests the relay will not operate. Note that for a 12 V supply you should increase the series resistor for the LED from 470 Ω to ~620 Ω, although 470 Ω will work, only with the LED being a bit brighter.
    HelpMe123 likes this.
  3. Bluejets


    Oct 5, 2014
    I have found in the past that some of these dc relays are polarity dependant on the coil.
    That might be worth checking also.
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    It is also worth checking if you have wires the switch correctly.

    Depending on how the switch connections are configured, the relay may be always on, never on, or turn on and off with the switch. Because your talking to us, we know it's not the third one.

    A bit of explanation about the switch. Logically you're looking for a 2 terminal device that has no connection normally, but had a connection when you press the button.

    However, that switch has 4 terminals. It is possible that you have chosen the wrong two. In the orientation shown on your image, you have it wired assuming that the left two terminals are only connected when the button is pressed.

    One common configuration for this type of switch is that the two terminals on the left are always connected, as are the two on the right. In this case you need to have the wires on the left and right sides. You could try that and see if the problem is resolved.

    If the problem remains unresolved, use your wiring as a switch. Disconnect one end of one wire from the switch and note which LED turns on with the power applied. Then reconnect that wire, but to the left of the existing wire. When power is applied the other LED should turn on. If this works then you have the switch wired incorrectly, or maybe the switch is broken.

    If you still haven't seen both LEDs on, then you have either wired the relay incorrectly, the voltage to the relay is insufficient to switch it, or maybe the relay is broken.

    I realise a text description may be hard to follow, but I can't draw you anything right now.
  5. Bluejets


    Oct 5, 2014
    Photo shows switch across the two 5mm spaced terminals which I believe for a tactile switch that this is correct.

    Difficult to know where the relay pins are with respect to the breadboard connections though, especially for the coil.

    Photo also shows the relay not energised.
  6. HelpMe123


    May 22, 2019

    Thanks for the answer. The Problem was indeed the supply voltage. I switched to a 12 V power supply and everything is working fine now

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