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Class : Apprenti
Posts : 2
Registered on : 03/02/2009
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Hi; excuse me for teh bad english...
I have a transformer with those specifications:
pri: 230V alternate 50Hz 55mA
sec: 7.5 V continue 500mA 3.75 VA
I have infrared leds but not have the specifications.
There are a possibility to use the transformer?
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Class : Apprenti
Posts : 7
Registered on : 29/01/2009
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Hi,
You can use this transformer. And If you do not know the specifications of the leds, do not exceed 50 mA. Forward current which is over 50 mA may burn your leds.
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Class : Apprenti
Posts : 2
Registered on : 03/02/2009
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and so how i can calculate the resistance in the led assembly wizard?
Is correct that ? I calculated now:
7.5 V +30% (so indicates the wizard)
in serial assembly
3x 100 Ohms resistor (i already have....brown-black-red and gold stripes)
3xled
one switch
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Class : Apprenti
Posts : 7
Registered on : 29/01/2009
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300 ohm is too much if you use 70 mA.
V=I.R=70mA x 300ohm= 21V !! Your power supply does not support this value.
If your led Voltage is 2 V, total led voltage is 6V in serial connection.
7,5V + %30 =9,1 V
9,1V - 6V=3,1 V for resistor.
3,1 V/70 mA = 44 ohm. You should use this resistor or near this value.
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