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10-02-2009, 11:44 AM   #1
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An easy question for your guys which is hard for me~ pls help~~

I tried put those light bolb together which are 6V2W, i tried to put them together with 9V 200mA power supply but it's not enough voltage for them or i should put the resistor on each bolbs but i really donno how to calculate and how many ohm that i should put.
so i tried 2 times with another power supplies.. 1 is 12V 0.3A ( not enough for V 7 light bolbs too) and 1 is 12V 1200mA (it was enough V for those bolbs this time) but they both were dead within 1 hr. so can somebody help me here?

Thank you very very much!

Last edited by Scuba_Dave; 10-02-2009 at 11:46 AM. Reason: removed links - entire text was linked

10-02-2009, 11:47 AM   #2
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What are you trying to do exactly?

10-02-2009, 11:50 AM   #3
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Quote:
 Originally Posted by Scuba_Dave What are you trying to do exactly?
I'm trying to do a little pond with lights around for my son, i finished the box for the pond already, but i failed to put those light on it... 2 power supplies was dead already~
Thank you~

 10-02-2009, 03:52 PM #4 Member   Join Date: Aug 2009 Location: Maryland Posts: 61 Rewards Points: 75 Along with SD, I'd like to help. However, I have only a vague idea of what you're attempting. Are you trying to light 6volt lamps which are 2watts each? If so, each lamp will draw about 350ma. (.35a). For seven of these bulbs a 6v/2.5a supply is required (one with a bit extra capacity for safety). Certainly with too low a voltage supply, you don't add resistance. The bulbs died predictably if you applied 12v to 6v bulbs, which at that time each would have needed a series resistor of about 15 to 20 ohms/3w. But that 12v/1.2a supply was still about half of what is needed. By the way, you don't need an elaborate power supply. A simple 6v filament transformer, easily obtained and inexpensive, will do the job. Have I helped? Last edited by oilseal; 10-03-2009 at 06:13 AM.
 10-03-2009, 08:44 AM #5 Member   Join Date: Sep 2008 Location: Oregon Posts: 1,497 Rewards Points: 500 Might want to search the internet and learn about LED lights. These use very little power. They sell some very bright LED's at Radio Shack (as well as elsewhere). Many LED's will need a resistor of about 1 K ohms in series so they don't burn out. Others come with the resistor already installed. With LED's, there is a + and a -. If it does not work, switch the wires around. These are ready to be connected to 12V DC power (don't need resistors)... http://www.superbrightleds.com/1157.htm
 10-03-2009, 08:53 AM #6 Newbie   Join Date: Oct 2009 Posts: 5 Rewards Points: 10 I'm thinking about to use LED too, it's more safety and easier.. Thank you for your suggest. I really so confused, because those lamps didnt' die, but 2 12V power supplies was dead if i turn on the light around a hr. but 9V power supply didn't die. i seems so doesn't make sense to me. because 12V is bigger than 9V. Thank you for everyone who gave me some suggests here! Thanks alot~
 10-03-2009, 10:38 AM #7 Member   Join Date: Sep 2008 Location: Oregon Posts: 1,497 Rewards Points: 500 Some power supplies have fuses inside them (the little black boxes you plug into an outlet). The fuses are not designed to be replaced. They are there to prevent overloading. And if used normally, they would never be overloaded and the fuse would never blow.
10-05-2009, 09:37 AM   #8
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Quote:
 Originally Posted by Billy_Bob Some power supplies have fuses inside them (the little black boxes you plug into an outlet). The fuses are not designed to be replaced. They are there to prevent overloading. And if used normally, they would never be overloaded and the fuse would never blow.
but the funny thing is 9V didn't get any overloaded... but 12 dead.

10-05-2009, 11:54 AM   #9
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Quote:
 Originally Posted by keifoo but the funny thing is 9V didn't get any overloaded... but 12 dead.
I suspect you overloaded all of the power supplies, but only the power supplies with fuses stopped working - fuses blew.

10-05-2009, 11:58 AM   #10
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Thanks so much Billy.... i just bought some LEDs with 470ohm resistor and a brand new 12V 500mA power supply and 1 extra 9V power supply in case this time... I hope it works..

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