# Thread: what resistor do i need

1. ## what resistor do i need

I have glb flight landing gear lever for 737 and it has an led for the knob which
requires 5v supply and resistor.
I will connect to a cpu 5v power supply but not sure what resistor i need.

Thanks

steve

2. ## Re: what resistor do i need

R = (Vs-Vl)/I

R = resistor size
Vs = supply voltage (5v in your case)
Vl = LED voltage (check this, if you're saying 5v, then the result equals zero)
I = LED current (usually 10 or 20mA (0.01 or 0.02A)

If you can't determine the values needed, go for a higher resistor and work down. Maybe try somewhere around 300 ohms first?

R = (5-2)/0.01 = 300

3. ## Re: what resistor do i need

Sorted,went with 330.

4. ## Re: what resistor do i need

Generally LED's are 2.2 - 2.6 volt devices and so we need to limit current on a 5V supply general good starting point is 330Ohms resistor
color code orange - orange - brown
then adjust up or down to get the light intensity you require - just be aware some LED's are low light efficiency if viewing from the side and so dont reduce resistor too far
hold on steve - I recognise you now and I know this is is solved - will leave the reply in for other members

5. ## Re: what resistor do i need

Originally Posted by UKV1342
Generally LED's are 2.2 - 2.6 volt devices and so we need to limit current on a 5V supply general good starting point is 330Ohms resistor
color code orange - orange - brown
then adjust up or down to get the light intensity you require - just be aware some LED's are low light efficiency if viewing from the side and so dont reduce resistor too far
hold on steve - I recognise you now and I know this is is solved - will leave the reply in for other members
Thanks Mike,
Yes I got the right resistor off Derek (flyuk) after my chat with yourself and derek,not forgetting young seans