Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

King bright LED

Status
Not open for further replies.
Hello,
I was reading data sheet for LED display..
there was Peak Forward Current 130mA i think it is for making more bright the LED To eyes?
As in my case i was connecting the Led Series with series R of 120 ohm so, following current was ~30mA or 20mA but for getting more bright there should be peak current so, how to do this is there any circuit for that?
 
Hello,
I was reading data sheet for LED display..
there was Peak Forward Current 130mA i think it is for making more bright the LED To eyes?
As in my case i was connecting the Led Series with series R of 120 ohm so, following current was ~30mA or 20mA but for getting more bright there should be peak current so, how to do this is there any circuit for that?
Like all LEDs, the peak current is allowed for only very short durations. If the display is multiplexed and one LED lights for a moment then turns off then the next LED lights for a moment then turns off etc, then each LED will be turned on only for a moment and its average current is low and it will appear dimmed. You can increase its peak current (but observe the peak current maximum duration rating) and it will appear brighter.
 
Hello,
That mean we can get more brighter the LED with same leds any way what is the procedure of circuit to this?
 
Hello,
That mean we can get more brighter the LED with same leds any way what is the procedure of circuit to this?
Please translate that into English.

An LED will burn out if the average current is too high. But if an LED is lighted for only a very short duration then it appears dimmed because our vision's sensitivity to brightness is slow. An LED dimmer uses the width of pulses to determine the brightness. But if you increase the momentary peak current then the LED will appear brighter until the average current is so high it causes the LED to burn out or not last long.

The datasheet for an LED shows the maximum allowed peak current for a certain short duration.

Modern LEDs are very bright. I recently bought a toy helicopter for $1.00 in Mexico. It has a red, green, blue LED with a microprocessor inside that flashes many bright different colors and at different rates. It had 3 tiny battery cells. It used a rubber band to shoot it high in the sky then it comes down slowly and spinning. I put its LED in a solar garden light and it brightly blinks its colors all night long from one AA Ni-MH battery cell.
 
Average current translates to heat. Peak current translates to how fast you can multiplex (duty-cycle) and also play a part in IR communication range.
 
When an LED display has its segments multiplexed, each segment is turned on only for a moment then the next segment is turned on then the next then the next. So each segment is lighted for only a small duration of the total time which makes it appear dimmed because its average current is very low. Is your display multiplexed?

You can increase the current of each multiplex pulse if you do not exceed the maximum allowed current and duration ratings in the datasheet then each segment can have a brightness that appears like the segment is continuously turned on at its maximum allowed continuous current.
 
You can increase the current of each multiplex pulse if you do not exceed the maximum allowed current and duration ratings in the datasheet then each segment can have a brightness that appears like the segment is continuously turned on at its maximum allowed continuous current.

Sir,
How to increase the current ?
and there are both multiplex and simple also!!
 
Sir,
How to increase the current ?
A knight is called SIR in England. I am not a SIR since I was not knighted by the queen of England. I never met the queen.

You need to learn Ohm's Law. Current= Voltage divided by Resistance. Resistance needed= Voltage divided by the amount of Current you want.
For example you have a 2.0V red LED that is normally continuously operated at 20mA. You are powering the LED circuit from a 5.0V supply. The current in the LED is limited by a resistor in series with it.
Since the resistor and 2V LED are in series from a 5V supply then the resistor has 3V across it. Then for 20mA the resistor value is 3V/20mA= 150 ohms.

An LED that is normally operated at 20mA usually has a maximum allowed continuous current of 30mA which will make it appear very bright. With a 2V LED and a 5V supply the resistor value to produce a current of 30mA is 3V/30mA= 100 ohms.
If you use less than 100 ohms then the LED will burn out soon.
 
I'd like to use this as an example, but not the RIGHT example. You can take a 12 V motor and drive it with PWM )pulse width modulation from nearly 0% to 100%. At all times the motor sees the peak voltage, but depending on the duty cycle it moves slower than it's rated speed.

Same sort of deal with a LED. If at 20 mA it's at 100% brightness, Then at 50% duty cycle it might be half that. It's harder to come up with 20 mA average current because of calculus concepts, but not too hard. So, at at SAY 200% (40 mA) and 50% duty cycle the LED is on at 100% brightness That 200%/2 IS 100% an the duty cycle reduces 50% more. so the LED sees 100% average, so it's the same as 20 mA continuous. Of course on for 1 hour at 200% and off for an hour doesn't make it last;

You vary the brightness by varying the duty-cycle. But the size of your array dictates and your eye's persistence dictates how fast you can do this. The datasheet puts limit on this too.

You can't get any brighter than the continuous current except for maybe brief instances.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top