Dear all,

Would you please help me with this circuit. I have a voltage source vary from 9V to 18V. I am using Osram LWE6SG .
Is it enough for turn on the LED?
If the circuit is not correct, would you please give me a reference (just simple because my PCB is very small 2x3mm).
I would very much appreciate any help or guidance you are able to give me.

Thanks,
Sunday

 

Well your circuit looks good but have you checked a power dissipation in current source?
Also are you gonna to use a single LED only?

 

Welcome to the forum!

my PCB is very small 2x3mm

So how are you going to mount D3? Its maximum dimension is 3.86mm and it requires 100mm^2 of 1-oz copper pad to handle 208mW max. With a 9V battery D3 will be dissipating ~180mW, which is uncomfortably close to the limit. With an 18V battery D3 will probably fry.

 

Well your circuit looks good but have you checked a power dissipation in current source?
Also are you gonna to use a single LED only?

Yes, I use single LED only.

Welcome to the forum!
So how are you going to mount D3? Its maximum dimension is 3.86mm and it requires 100mm^2 of 1-oz copper pad to handle 208mW max. With a 9V battery D3 will be dissipating ~180mW, which is uncomfortably close to the limit. With an 18V battery D3 will probably fry.

I need a simple constant current source that provides ~30mA current from a 9-18V source, because this source is come from the other design that I cannot approach.
Would you please refer me another circuit that can drive this led?

Thank you so much for your help.

 

This will do what you need if it is not to large.
You can use the sot223 package.
http://www.mouser.com/ds/2/405/lm317-373199.pdf

 

I"m sorry, my PCB is 2x3 cm.

 

I"m sorry, my PCB is 2x3 cm.

Then the circuit above should work. :=)