No effect even though I add one more.

Discussion in 'The Projects Forum' started by Lightfire, Dec 21, 2010.

  1. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010

    I was experimenting last day or so. I tried to connect one more bulb through a parallel circuit. When I add it, the other bulb is becoming low bright. When I remove it, it becomes bright and back to it normal brightness.

    Now, I tried to connect the two bulb via connecting in directly from a battery. I did not make it any circuit, whether it is parallel or series. When I add one, the bright of one bulb is still a normal. Nothing change. When I remove one, still nothing change.

    So means that, if I will directly add all the devices into a battery, the power is the same on each other?

    Also, I bought an electric fan. It have three wires. The one is black, the another one is red, and the last and the one that I do not know is the white. My teacher told me that it is for the ground, I mean earth.

    Also, when I connect the electric fan opposite. I mean, I connect the black wire to positive terminal of battery and I connect the red wire into negative terminal of a battery then it do not work. But when I add it correctly, it work okay. No problem. Why it is like that?

    Sorry for a bad English grammar. I am brother of the said name.:)

    Thank you a lot.
  2. hgmjr

    Retired Moderator

    Jan 28, 2005
    You need to provide more details.

    What is the type of light you are using? (LED, Incandescent, or other) What is the voltage of the light you are using? Can you supply us with a part number of the bulb?

    I understand from your post that you are the brother of lightfire.

  3. retched

    AAC Fanatic!

    Dec 5, 2009
    Model number for the fan?

    Also, many 3 wire fans use the 3rd wire for speed.

    It could be a high/low Where red is HIGH and blue is LOW, or it could be a RPM gauge.
  4. SgtWookie


    Jul 17, 2007
    It sounds like the addition of the 2nd bulb may be too much of a load for the battery - either that, or you are actually trying to connect the two bulbs in series, and each is only getting 1/2 the voltage it normally gets.

    It has to be SOME kind of circuit, or nothing would happen!
    You have a power source, and you have two light bulbs, and some wire.
    You are connecting them to the power source somehow in order to get them to light up.

    I think that in this case, you have connected the bulbs in parallel to the power source, and in the previous case where the 1st light was getting dim, you were connecting them in series.

    If each device has two connections to the power source, then they are connected in parallel.

    Is this fan for computer cooling, and rated for 12v?
    Usually, such fans require +12v on the red wire, GND (or power return) on the black wire, and the white wire is used to signal the computer the fan's RPM (speed). Sometimes the 3rd wire has different functions than a tachometer.

    These fans are BLDC (brushless DC) motors, and will only run in one direction.

    They are designed to only spin in one direction. They usually have a protection diode in them in case the power is connected backwards. The fan blades are designed to be efficient in moving air in one direction only.

    Welcome to All About Circuits. You should create your own login account; it is easy to do.
  5. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
    Firstly, I would like to introduce myself. As I said earlier, I am brother of the said name. Yes, it is. I will make a thread which introduces myself.;)

    So here we go then.

    I made an image of a simple circuit. I am very sorry if it is looks like that I made it rush. Because I am not good in editing photo.:p

    As you may see, the two bulb was lighted. They are both simple circuit. Am I right? Why I think they are both simple circuit? Because their wires are directly put in battery. I do not know then.

    But anyway, whether it is parallel, series or simple. The question is, why when I make it in parallel, when I add one more bulb, the current bulb is becoming not bright anymore, when I remove it becomes bright and back to it normal dim.

    When I make it in simple circuit, circuit that shows in attachment, no matter if I add or remove. The dim of every bulb are just the same. Nothing changes and happen. Even though I add an electric fan which is consuming more power (Am I right?:p)

    As for the electric fan, yes it is 12 volts and it is the fan from the computer.

    Thank you.:confused:
  6. SgtWookie


    Jul 17, 2007
    From the image you provided, you are connecting the bulbs in parallel.
    Incandescent lamps (those in a glass bulb with a tungsten filament) are power-hungry. It seems that your battery is not able to supply enough current for both lamps at the same time.
  7. wayneh


    Sep 9, 2010
    Your circuit as drawn would be called parallel, but I understand your term "simple", as in "direct". I'm not sure what you did to make your "parallel" circuit but I suspect there is something that is adding resistance and reducing current. For instance, two bulbs on one thin wire will dim compared to one bulb each on its own wire. If you have a voltmeter you could show this - you will see a voltage drop across the wire itself while the bulb is lit. What is the power draw of your bulbs, and gauge of your wire?

    Depending on what bulb you are using, it probably draws more current than your fan. Most simple two-wire DC fans will spin in reverse when connected reverse polarity. Your third wire is most likely for rpm measuring or control, and this requires the polarity to be fixed in one way.