LED Camera Flash

Thread Starter

chsaer74

Joined Jan 26, 2007
2
Hello all,
I am new here but have been in electronics for about 10 years.

I have a circuit that i am trying to design for my daughters dance studio. the circuit will be used in a Men In Black type nuralizer for some kids. I need to make it safe for them which is why I am Using Low Voltage LEDs. I have ran into several problems. the first beign that all of the LED boost ICs I have found are to small and require me to purchase them in qty of 3000 when i only need 20. if anyone can point me in the right direction it would be greatly appreciated. I have searched and am about to go insane. there are alot of nice cicuits out there but they all seem to be using ICs that require a min of 3000 to purchase. again thanks for the help
 

beenthere

Joined Apr 20, 2004
15,819
Hi,

Could you tell us what a "LED boost IC" is? You might want to look into Volume III of the on-line E-book associated with this site and look at the LED information under diodes.
 

Thread Starter

chsaer74

Joined Jan 26, 2007
2
The main IC i am finding is a NCP5007 made by onsemi.
The NCP5007 is high efficiency boost converter operating in current control loop, based on a PFM mode, to drive White LEDs. The current mode regulation allows a uniform brightness of the LEDs. The chip has been optimized for small ceramic capacitors and is capable of supplying up to 1.0 W output power.
this is taken form their web site. i will see if the ebook will help any.

EDIT: I look at the ebook and i understand how LEDs work. What i am trying to do is get a Flash out the LED by pressing a button without having the charge a cap first. The circuit i am trying to duplicate would be the same thing used in cell phones for the flash. i need to make this as low of voltage as possible due to the fact that samll kids will be using them and we don't want anyone to get hurt
 

beenthere

Joined Apr 20, 2004
15,819
Hi,

LEDs take very low voltages for conduction. White (actually blue LEDs with a yellow scintillation layer) will conduct with a voltage of about 2.4 volts applied. After that, it's just limiting the current.

For a flash effect, you need to put a fairly high current (20 to 40 milliamps) through the LEDs for a brief time (10 milliseconds or so). A couple of AA battries will supply the voltage & current for this. C cells will lst longer. That's absolutely safe.
 

thingmaker3

Joined May 16, 2005
5,084
Beenthere makes things so darn easy!!

neuralizer.jpg

With S1 open, C1 charges through R1 to 3vdc. Closing S1 discharges C1 through LEDs. 3-2.4=0.6vmax across R1. 0.6/15=40milliamperes. 680uF*15ohm=10.2milliseconds; after 10.2 milliseconds, current will have dropped to about 14.75 milliamps.
 
Top