Author Options:

How to Lit a 1watt LED using a NOKIA charger Answered

I would like to lit 1w Power LED using NOKIA Charger.

Mostly, a 1watt Power LED's specification is 3v0~3v4 DC Volts and 350mA Current.

Printed specification on Charger Cabinet it is for - Input 100/240v 50~60 Hz…„ Output 5.7v/800mA.

For Series Resistor's Value…„ if we calculate upon Ohm's Law - for VoltageSupply, Vs 5.7v…„ ForwardVoltage, Vf 3.3v…„ ForwardCurrent, If 330mA to lit single LED. In Result we can use a Standard Value of Resistor 7.5 Ohm and because of Resistor's Power Dissipation 792 Milliwatts, can use a 1watt.

In series I planted 10 Ohm 1w Resistor instead of 7.5Ω. LED lit up in normal. Neither too much nor too little shining. But…„ about two and a half hours later it was flashing. I switched it's off and checked that the charger unit also became hot.

Where I made mistake…?

Please HELP how to lit this 1watt LED using this NOKIA charger.

I also have one another charger with printed specification on cabinet it is for - Input 100~240v 50/60Hz…„ Output 5.2v/400mA. I also want to use this for one another 1watt Power LED to lit. Please help for this too.

please ignore my  bad english.

3 Replies

iceng (author)2017-01-31

Like Downunder said use a proper constant current driver.

What I think is the Nokia charger is not designed for continuous operation, (typical -minimum-cost-design) and expects a slowly diminishing load as the battery reaches full charge.

Then when the LED warmed up, it lowered its nonlinear resistance and pulled a little more current as Downunder pointed out would happen... This heated the Nokia charger a little more and the protective temperature circuitry shuts the charger regulator OFF to prevent irreversible damage to it.. Then when it cools just a little bit the protect circuit turns the output back ON only to get too hot again etc etc etcetera.. Making the LED blink.

Select as Best AnswerUndo Best Answer

free2atc (author)iceng2017-02-02

@iceng sir…„

Very nice answer,
completely comprehensible for me.

Select as Best AnswerUndo Best Answer

Downunder35m (author)2017-01-30

You need a suitable LED driver, everything else won't be good enough in the long run.
Without a "costant current driver" the temp changes during usage will cause the LED to get a lower resistance.
That means more current is drawn, heats up more, more current....

Select as Best AnswerUndo Best Answer