[SOLVED] Capacitor value for LED fading

Using Arduino General Electronics
21

Noobian:
Ok.

4K7 - the value of capacitor or resistor? why they are both 4.7K? does both have to be same value?

I just googled, "4K7" and got the answer.

22

aarg:
I just googled, "4K7" and got the answer.

the cap is also 4.7k

23

the cap is also 4.7k

No it is not.

The capacitor is 4.7mF only no one uses mF as a unit of capacitance, so it is normal to say 47000uF

does both have to be same value?

No.

24

Grumpy_Mike:
No it is not.

The capacitor is 4.7mF only no one uses mF as a unit of capacitance, so it is normal to say 47000uF

No.

47000uF or 4700uF?

is it the resistor value or the capacitor value deciding how long it takes for LED to fade?

also will the power from the cap damage the LED, so do I need a resistor between cap and LED too?

25

is it the resistor value or the capacitor value deciding how long it takes for LED to fade?

Both.
The units of resistance times the units of capacitance equals the unit of time.

So RC ( Resistance times Capacitance ) is often known as a time constant.

also will the power from the cap damage the LED,

Only if you let too much current flow.

so do I need a resistor between cap and LED too?

Yes, but that is not what you asked, you asked how he did it in that video. You would have known how if you had clicked the "more" under the video and followed the links, but you didn't.

47000uF or 4700uF?

Yes sorry 4700uF ( micro Farad or ten to the minus 6 of a Farad )

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Grumpy_Mike:
Both.
The units of resistance times the units of capacitance equals the unit of time.

So RC ( Resistance times Capacitance ) is often known as a time constant.
Only if you let too much current flow.Yes, but that is not what you asked, you asked how he did it in that video. You would have known how if you had clicked the "more" under the video and followed the links, but you didn't.
Yes sorry 4700uF ( micro Farad or ten to the minus 6 of a Farad )

ok

his schematic didn't have a resistor between led and cap

so if i make it, shall i use a 4.7k resistor between led and cap, or any other value?

28

dlloyd:

is the led in wrong direction?

29

is the led in wrong direction?

No.

30

I guess that's it :slight_smile:

Thanks for all your help and support.

31

I guess that's it

Until you try it and find the LED comes on the instant the relay closes and then fades off. Is that what you want?

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