led forward voltage ? - Page 3 - Electronic Circuits Projects Diagrams Free

ronsimpson · 31st October 2009, 05:20 PM

This is from National's data sheet.
LM317 can be used as a voltage or current regulator.
The LM317 tries to make 1.25 volts between ADJ and Vout.
In current mode it will sent current to the load (LED) untill there is 1.25 volts through the resistor.
1.2 ohms = 1 amp
12 ohms = 100mA
The regulator needs Vin to be > Vout by a couple of volts.
The LM317 will get hot so add a heat sink.

bublee · 1st November 2009, 02:38 PM

I hav tried above circuit n found that along with constant current this circuit also provides sufficient forward vltg for almost 4 LEDs......... this one is good

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31st October 2009, 05:20 PM	#31
ronsimpson	This is from National's data sheet. LM317 can be used as a voltage or current regulator. The LM317 tries to make 1.25 volts between ADJ and Vout. In current mode it will sent current to the load (LED) untill there is 1.25 volts through the resistor. 1.2 ohms = 1 amp 12 ohms = 100mA The regulator needs Vin to be > Vout by a couple of volts. The LM317 will get hot so add a heat sink. Attached Thumbnails

1st November 2009, 02:38 PM	#32
bublee	I hav tried above circuit n found that along with constant current this circuit also provides sufficient forward vltg for almost 4 LEDs......... this one is good