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Red LED Fader help

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Hero999

Banned
What about just connecting another two LEDs plus 100R resistor in parallel?
 

audioguru

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The base voltage of the transistor goes up to +6.5V. Its emitter goes up to 5.7v. Each red LED is about 1.8V so 2.1V is across the 100 ohms which is an LED current of 21mA.

Higher power LEDs have a higher voltage so the dimming will not be correct unless a higher battery voltage is used which will cause the transistor to get hot.

Use a 12V supply with 2.5V high power red LEDs.
The base of the transistor will go up to 8.7V. If the max LED current is 60mA then the transistor dissipates 198mW which is warm, not hot. The emitter voltage will go up to 7.9v and the current-limiting resistor will have 2.9V across it. For a max current of 60ma the resistor value should be 2.9V/60mA= 48.3 ohms. Use 51 ohms/one-quarter W.
 

amalfushi

New Member
could i get you to clarify so that even an art major could understand (because i am one, lol). Thanks a bunch for your help
 

audioguru

Well-Known Member
Most Helpful Member
I said what needs to be said. If you don't understand Geek-talk then do Art instead of Electronics.
 
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