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Newly Enlightened
I know you guys are eager to get a very reliable constant current source to drive LED's. I found an ideal device to make a simple constant current source easily programmable while requiring very few external components.
1) The device is ST890 from ST Microelectronics. You can find the datasheet from www.st.com. Click products, key-in 'st890' at P/N search, click PDF file to see the sheets.
2) This device is a linear device. The input voltage is 2.7V-5.5V, current adjustable upto 1.2A.
3) This device is suitable for 3cell NiCad/Ni-MH or 1 cell Lithium Ion battery. It can be used with 3 cell Alkaline batteries but I recommend to use Ni-MH or Li-Ion as the voltage stays at 3.6V most of the running period and so the power loss is minimal. Not for 3V Lithium battery(CR-123)!
4) You just select a resistor to fix the current required. Easy!
5) This can be used to run upto 3 1watt Luxeon LED's in parallel. It may require small resistor in series to balance the current thru individual LED's which may have slightly different Vf.
Cheers...
1) The device is ST890 from ST Microelectronics. You can find the datasheet from www.st.com. Click products, key-in 'st890' at P/N search, click PDF file to see the sheets.
2) This device is a linear device. The input voltage is 2.7V-5.5V, current adjustable upto 1.2A.
3) This device is suitable for 3cell NiCad/Ni-MH or 1 cell Lithium Ion battery. It can be used with 3 cell Alkaline batteries but I recommend to use Ni-MH or Li-Ion as the voltage stays at 3.6V most of the running period and so the power loss is minimal. Not for 3V Lithium battery(CR-123)!
4) You just select a resistor to fix the current required. Easy!
5) This can be used to run upto 3 1watt Luxeon LED's in parallel. It may require small resistor in series to balance the current thru individual LED's which may have slightly different Vf.
Cheers...
