How to Lit a 1watt LED using a NOKIA charger


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.

iceng8 months ago

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.

free2atc (author)  iceng8 months ago

@iceng sir…„

Thanks;
Very nice answer,
completely comprehensible for me.

Downunder35m8 months ago

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....