LED tracffic sign

[amindzo]

Hi, i want to make a traffic sign LED and i want to turn on 19 LED. every LED consume 20-25mA and i need to design a power source that give every LED just 20mA. could yoy help me with this? how should i connect the LED's? parallel or series&parallel?

 

[colin55]

Both......

 

[amindzo]

could you help me more? i think for 19 LED parallel is better.

 

[colin55]

NO..........

 

[MrDEB]

LED Resistor Calculator
Need specs on desired LEDs.

 

[amindzo]

should i use resistor to limit the LED current? resisitor is increase the power consumption, is there a better method? power consumption is very important for me, because we want to use solar cell and battery for this LED traffic sign.

 

[ronv]

What is the voltage available to drive the LEDs. What is the forward voltage drop of the LEDs. With those numbers some ideas will come.

 

[crutschow]

For best efficiency you need to use a switching constant-current supply for the LEDs such as one of these.

 

[amindzo]

our supply voltage is 6 volt and LED's need 2.5 to 3v and 20ma. i want to turn the LED's on and off every few seconds to reduce power consumption. are these switching constant-current supply IC's have this application or i need an extra circiut or microcontroller for this?

 

[ronv]

Since the voltage drop across the diode is 3 volts you can't put 2 in series so it needs to be one each. You could put a 150 ohm resistor in series with each one. This would waste about .06 watts each or a little over a watt for the 19 leds. If that power waste is to much you would need the LED driver solution. You will need something to turn it on and off - either hardware timer or a micro.

 

[4pyros]

You could do two in series and limit the voltage to 2.5 volts each and use a resistor to drop 1 volt at 20ma and a diferant resistor to drop 4 volts at 20 ma for the last LED. Andy

 

[amindzo]

i want to make something like this and i want to know that what kind of LED do you suggest?

 

[4pyros]

that would depend on what are going to use to for traffic?

 

[amindzo]

i have done this and it works well for 44 LED, but there is a problem. if one LED is going out of order we have 4 LED off (one row is turning off) what can i do to solve this problem? (if one LED is out of order only one off LED)

 

[colin55]

We use a 3v9 zener across each LED to keep the other LEDs on when one fails.
It's a lot of extra componentry but is needed when you have long strings.

 

[4pyros]

Or use one resistor per LED, But you have not told use what this is for, who brite does it need to be? Andy

 

[ronv]

This one has a fairly wide viewing angle and is pretty bright. I think there are some Chineese parts that are similar.

https://www.electro-tech-online.com/custompdfs/2010/10/OVFSRAC8PDF.pdf

 

[amindzo]

i want this for traffic sign so i will use solar cell and battery charger and battery for this project. power consumption is very important for me because it should work without solar cell in the night and without the electricity so you think the zener diodes are a good idea?

 

[4pyros]

amindzo; Google "Joule Thief" this is what you need to get every bit out of your battery. Andy

 

[blueroomelectronics]

You can buy such a sign for about $300 US.
Solar Power LED Traffic Signal Board products, buy Solar Power LED Traffic Signal Board products from alibaba.com