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 Post subject: 4.5W infrared security projector
PostPosted: Tue Mar 29, 2011 4:39 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
Today I bought some powerful IR LEDS for security projector for night vision cameras.
It will be powered from 12V battery. Constant current source is controlled by light sensor.


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 Post subject: Re: 4.5W infrared security projector
PostPosted: Fri Apr 01, 2011 2:17 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
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Location: Pleasant Hill, California
It works.
When I close the LDR by finger it lights up. What is interesting, my photo camera sees 850 nm IR lights with purple color. Smile


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А женщина даже в мужской рубашке выглядит гораздо приличнее, чем мужчина в женских колготках! Be-be-be!
 
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 Post subject: Re: 4.5W infrared security projector
PostPosted: Fri Apr 01, 2011 3:34 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
Corrections: BJT is 2SC1815, MOSFET is IRF3710, instead of R1 and R2 a single resistor 56K. R5 omitted (no oscillations).

Also, I paralleled each 3 LEDs, in case if one dies.

Let's see how it works in the darkness...

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А женщина даже в мужской рубашке выглядит гораздо приличнее, чем мужчина в женских колготках! Be-be-be!


 
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 Post subject: Re: 4.5W infrared security projector
PostPosted: Fri Apr 01, 2011 9:40 pm 
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Posts: 238
can please explain role of Q2? I have made a similar circuit but with Q2 omitted, and using a relay instead of LEDs.


 
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 Post subject: Re: 4.5W infrared security projector
PostPosted: Fri Apr 01, 2011 10:29 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
quikie22 wrote:
can please explain role of Q2? I have made a similar circuit but with Q2 omitted, and using a relay instead of LEDs.


Q2 sets constant current through LEDs. It is a constant current source that is switched off when LDR sees bright enough light.

By the way, LEDs I bought on e-pay are really bad... The seller claimed in the item description they are for 140 mA, but what he shipped me, die on 60 mA only (well, some of them), and intensity of light is not enough for the camera.

I bought 20 bags! Now I have a lot of 1.5V stabistors, to use in cathode bias of tubes, instead of LEDs for ID projectors...

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0543620250

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 Post subject: Re: 4.5W infrared security projector
PostPosted: Fri Apr 01, 2011 11:49 pm 
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That wasn't very honest of the epayee.... as always, caveat emptor.

Anyhow, I think I will be expecting a lot of LED biased tube designs from you for now Wink. The only problem is, you can't "see" if they are conducting or not as they are IR, or else you need to use your camera to see if they light up.

Anyhow, why not try them at a lower current? Maybe at 50ma.

OK, I see the role of Q2 now. I was using a relay, so there was no need for a constant current, either on or off. With the LEDs, the current would change with the amount of light hitting the LDR, so you needed to set a constant current source to ensure a stable brightness of the LEDs.


 
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 Post subject: Re: 4.5W infrared security projector
PostPosted: Sat Apr 02, 2011 9:44 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
quikie22 wrote:
That wasn't very honest of the epayee.... as always, caveat emptor.

Anyhow, I think I will be expecting a lot of LED biased tube designs from you for now Wink. The only problem is, you can't "see" if they are conducting or not as they are IR, or else you need to use your camera to see if they light up.


Actually, I can: they look red (850 nm) in darkness.

Quote:
Anyhow, why not try them at a lower current? Maybe at 50ma.


They are too dim even on 60 mA, unusable for IR illumination.

Quote:
OK, I see the role of Q2 now. I was using a relay, so there was no need for a constant current, either on or off. With the LEDs, the current would change with the amount of light hitting the LDR, so you needed to set a constant current source to ensure a stable brightness of the LEDs.


Yes, it's role is to limit the current on stable safe for LEDs level. I bought some from another seller, let's see... Anyway I need this project, my friend who is a security and investigations guy wants it.

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 Post subject: Re: 4.5W infrared security projector
PostPosted: Tue Apr 05, 2011 1:12 am 
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Joined: Fri Mar 19, 2010 8:59 am
Posts: 21
wavebourn wrote:
By the way, LEDs I bought on e-pay are really bad... The seller claimed in the item description they are for 140 mA, but what he shipped me, die on 60 mA only (well, some of them), and intensity of light is not enough for the camera.

I bought 20 bags! Now I have a lot of 1.5V stabistors, to use in cathode bias of tubes, instead of LEDs for ID projectors...

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0543620250


Smile Good thing is IR are the best for that, from a theoretical electrical standpoint at least that's what I read somewhere... then the old, 1,6V low intensity red ones.

I'm eager to read your findings between different kind of LEDs once you experiment!


 
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