capacitor and fading led

232

03:40:45

 \When the switch is closed the capacitor charges and the led lights  When the switch is opened the capacitor discharges keeping the led alight for a short time fading to off.

in everycircuit
with timing set to s/s you can't see a fade 
with timing set to 10 ms/s there is a fade

switch 2 allows you to see the circuit without the capacitor 

timing 10 ms/s 
550uF ≈ 1/2 second to fade
1.1mF ≈ second to fade
2.2mF ≈ 2 seconds to fade
4.4mF ≈ 4 seconds to fade
4.4mF ≈ 8 seconds to fade

Breadboard
power 5v 
resistor  1kohm
capacitor 47uf  
led lights brightly   fades in 1/2 second

everycircuit    
timing s/s
power 5v 
resistor  1kohm
capacitor 47uf          
led hardly glows       <<    why

video 
www.youtube.com/watch?v=4Hg7SLhetXM

published 4 years ago

wyoelk

4 years ago

One thing, the default setting for LEDs in this app is 2v and 20ma. So the current limiting resistor would be as follows; 4.82v-2v=2.82v÷20ma=141 ohms or 150ohms

wyoelk

4 years ago

This one has an inductor to show more circuit properties _ _ http://everycircuit.com/circuit/6011425823391744

Malcolm_McGrath

4 years ago

wyoelk :-) I do like the lc oscillator

Malcolm_McGrath

4 years ago

wyoelk I understand how you calc the resistance for the led R=V/I, thanks. My current issue is coming to terms with capacitors why and how/why to choose particular cap . Got some nice formulas and vids but is still greek to me.

wyoelk

4 years ago

Well it more "geek" to me cause I don't really get it either

mlira

4 years ago

Have a look at https://www.allaboutcircuits.com/textbook/direct-current/chpt-16/voltage-current-calculations/

mlira

4 years ago

If you just want to have an led light up it slowly it's easier to have the capacitor control a transistor or something else rather than powering the led directly. That way you can use much more reasonable values for longer delays.

mlira

4 years ago

Something like... https://everycircuit.com/circuit/4705992337784832

Malcolm_McGrath

4 years ago

miira :-)

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