Simple LED question

[ppadru1]

I am planning an awesome LED suit for halloween. I guess my question is, what kind of power would be required for 100 LED's to BLINK for several hours (6-7 hours). How difficult would it be to build a circuit which maybe creates a pattern in the blinking of the LEDs?

Sam

 

[rezer]

What color of LEDs are you using? This will determine the over-all current draw from the source. But more importantly, the configuration.
Depending on the configuration of the LEDs, if you have them wired in a series/parallel configuration, that is, having 5 wired in series with multiple branches of 5 LEDs for a total of 20 branches, you could use a 12V 2AH battery. Simply put, it will deliver 200mA with this configuration (calculated at 10mA/branch). This will give you enough power with your time requirements. Your battery should last for 10 hours. However, for a higher current draw, you would need a bigger battery. I would use less than the maximum current requirement of the LEDs (it may be around 20mA). 10mA if fine. For this then, I would use a resistor in each branch of 330 ohms, 1/4W. This will provide ample ratings no matter the color or rather forward voltage drop.
You can use a PIC microcontroller as a pattern generator to control the timing and patterns of the LEDs. But then you will also need a voltage regulator. So this then would also dictate the configuration and power requirements of your LEDs base on a 5V source instead of 12V. You probably would not want to use a transistor to switch the LEDs in that this would add complexity and bulkiness to your suit. But then with a 12V battery in your rear end, you may not care. Perhaps its a clown suit in which case you have plenty to work with. In any case, using a PIC to drive transistors for controlling the LEDs you can still use the 12V calculations above.

 

[Hero999]

If you want the LEDs to all blink in phase then use a flashing LED driving a transistor connected to all the LEDs.

If you want them to all flash out of phase with each other then, just use a flashing LED in each group of LEDs.

Don't forget that if they flash at 50% duty cycle it will last twice as long for the same current draw.