Maker Pro
Maker Pro

Flashing 5watt led?

CDRIVE

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May 8, 2012
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I'm not even going to try to understand that statement but I'll take your word for it. :)

Chris
 

CDRIVE

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Sounds good. Put it up on youtube.

Chris
 

samsm255

Dec 29, 2012
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I did it again with the leds hooked up and they are flashing faster than what the voltage meter is telling me. So guess this was really nothing after all. Just the meter trying tell me something.

Here the video anyway
 
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CDRIVE

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Hey, thanks for the vid! Yeah, a DVM can't respond accurately to pulses that short. Too bad you didn't keep the cam on the LEDs longer. Since everything I post here is simulated I never get to see the final (real thing) circuit actually working. :)

Chris
 

CDRIVE

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Yes, I'd appreciate that.

Chris
 

CDRIVE

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The LEDs flashing.

Chris
 

Harald Kapp

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To verify the basic coincidence of calculation/simulation and the real thing, reduce the flash rate by a factor of 10 (the DVM is too slow, as Chris rightfully mentioned). You should now see a good coincidence between the LEDs flashing and the meter's reading. Once you have verified this, you can go back to the fast flash rate.
 

CDRIVE

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I'm impressed with you!! We rarely get to see the end product. Cool!

Chris
 

samsm255

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I've got nothing to hide other than side I soldered on :p Also I don't see why you rarely get to see the end product. I know for sure I couldn't have done this stuff with out your and others help
 
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samsm255

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Side question..The leds are not bright as they seem in the video maybe 45% less bright as the video makes it. Is there anyway make them more bright? What would happen if we did something to the R3 resistor? (R3 between Led + and the + power wire)
 

CDRIVE

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The data sheet for that LED is a bit odd. Typically components are rated with at least two current maximums continuous and pulsed with PW being specified. I see only 700mA Max listed so that's what we'll work with.

You can place another 5R/2W resistor in parallel with R3. This will double your current. Keep in mind that the LEDs will be running at their max.

Chris
 

samsm255

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I just did that and the brightness of the lights didn't change at all. Looked up parallel resistors and guess I did it right. Photo below is what I did
 

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Harald Kapp

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Maybe the power source is at it's current limit? Try a big electrolytic capacitor in parallel to the power supply.
 

(*steve*)

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You may find that increasing the ON time will increase the apparent brightness.

This is only going to have real effect if the ON time is less than 100ms.

Your eye effectively integrates what it sees over a short time period, so a flash of shorter duration appears to be less intense.

Electronic flash is another example of this.
 

CDRIVE

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Maybe the power source is at it's current limit? Try a big electrolytic capacitor in parallel to the power supply.

Not a bad thought but I think Sam is using D cells or C cells. If he had room for one it would be a good idea regardless but I think Sam's housing may negate that.

Sam what are you using?

You may find that increasing the ON time will increase the apparent brightness.

This is only going to have real effect if the ON time is less than 100ms.

Your eye effectively integrates what it sees over a short time period, so a flash of shorter duration appears to be less intense.

Electronic flash is another example of this.

I think my original circuit gave Sam a pulse width = 50mS but I reduced it to 10mS after reading this suggestion from someone who someimes sports weird facial hair. :p

Sam, try increasing R5 to 120K. This will increase the pulse width to 90mS. ;)

Chris
 
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samsm255

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Im using 4 D's right now for power. And I need to replace R5 with a 1/4w 120k resistor? And should I keep the other resistors in parallel still with R3?
 
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