I tried to connect a 12V fan and a 3V LED to a 9V battery. But I did not get the required power for the fan. So I connected 2 batteries in series. When I connect the fan alone, it draws the required power. But when I connect the LED along with it, the fan turns slower than before. However, I would like to maintain the speed of the fan. This is for a project to make a unit that looks like fake flames. So I need the fan to maintain some good RPM so that the cloth that I will attach later flutters well and looks like a flame. I am new to this. Please help.

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    \$\begingroup\$ 1) A PP3 battery (I'm guessing that's what you used) won't last very long running a fan which is powerful enough to flutter cloth. You could use eight AAA cells and get a much longer running time. 2) It is important to limit the current through an LED to prevent it from burning out - what current does your LED need according to its specification? \$\endgroup\$ – Andrew Morton Sep 24 '16 at 18:11
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    \$\begingroup\$ @Vigneshwaran, the first thing to understand is that electronics is not "plug and play". You need to carefully choose and understand each part you are using or you will get failures and explosions. Explosions are fun but not the desired outcome. An LED is a component with various needs, one of which is something to act as a current limiter (normally, a resistor). You have a 9 volt battery and a 3 volt LED. As a circuit designer, you need to put something there to deal with the other 6 volts, effectively. \$\endgroup\$ – Ian Bland Sep 24 '16 at 18:50
  • \$\begingroup\$ Thanks. I had purchased a 1Kilo Ohm resistor just in case. Will try and add that to the equation. \$\endgroup\$ – Vigneshwaran Srinivasan Sep 26 '16 at 2:07

It seems that you are trying to connect the led directly to the 12V thereby reducing the voltage due to the internal resistance of the two batteries. That is not the way. Remenber also that 2 batteries of 9 V can make the ventilator turning but also there the voltage will drop. If this is the case place a resistor in series with the led. Let us say put some 560 ohm in series with the led and try again. It is better to look for a proper 12V supply.

  • \$\begingroup\$ Thanks @Decapod. I had purchased a 1 kilo Ohm resistor just in case. Will try adding that to the equation. I dont want to use a 12V battery for the simple reason that This is for a stage production. Kids are gonna use the torch and that too as stage props. Having them carry heavy things on stage is not desirable. \$\endgroup\$ – Vigneshwaran Srinivasan Sep 26 '16 at 2:05
  • \$\begingroup\$ If your happy with my answer please upvote and accept \$\endgroup\$ – Decapod Sep 26 '16 at 3:20

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