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Author Topic: LED strip dimming off circuit  (Read 5907 times)

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HTF

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LED strip dimming off circuit
« on: February 24, 2011, 14:48:22 PM »
Hello, sorry if i post without a search but i need help and i need it as soon as possible!
My idea is to make 1m led strip (3nm the square ultra bright led's) to fade out in a matter of like 3-5 sec after the door has been opened and closed.

To begin with i though of connecting transistor to the switch that runs the light on when door is open, so it will turn my circuit on without getting the original circuit with its load. The power supply is 13.3v (in car) the led's are separated into 2 stripes each (50cm) and connected between eachother! I'm not aware about the number of led's per strip because i haven't bought it yet!
So please help me to make a circuit that can make the lights dimm including the components list with exact names! : ) I will be glad if you gonna help me guys!

The main problem ive got stuck is with that: http://pcbheaven.com/circuitpages/LED_Fade_In_Fade_Out_Dimmer/
and that:http://pcbheaven.com/circuitpages/LED_Off_Delay/

I cant understand if any of these 2 are gonna be able to make the job for my circuit!
Also the capacitor value confused me a lot!

kam

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Re: LED strip dimming off circuit
« Reply #1 on: February 24, 2011, 16:33:08 PM »
the first one (LED Fade-In Fade-Out Dimmer) is not proper for you,because it has also a fade-in function that you do not need. So you need to go to the second circuit, the LED Off Delay with dimming effect.
The capacitor along with the resistor R3 controls the delay time. You need to start with a 100uF capacitor. I do not understand why you are confused with this. The larger the capacitor, the more the off-delay.

BUT:  i need to know more info about the LED strip. Answer the following:

1. Suppose that you do not use off delay circuit. Can you connect them directly to the battery and work?
2. Each strip is 50cm and you are going to use 2 strips?
3. What is the power consumption of each strip (watts or amperes)
4. What is the nominal voltage supply? (i suppose 12 volts for car battery)
5. does the manufacturer say that you need to connect a protective resistor?
6. is there any link to see these LED strips?


HTF

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Re: LED strip dimming off circuit
« Reply #2 on: February 25, 2011, 13:43:48 PM »
1) Connecting them to positive and negative turns them on, they are connected in a circuit with resistors so they work from 12v.

2) its one strip of 1 metter that you can split each 3 leds, 3 leds are connected into the same circuit and all go   + to +    - to - they still gonna work from 12v, even if you connect just 3 leds they work from 12 volts.

3) Found a source where leds look just like mine. Comsumption Watts Per Piece: 20ma.
Source: http://www.alibaba.com/product-free/104744428/Flexible_strip_60_Warm_White_SMD.html

4) 12volts or even 13.3 from a car battery.

5) No, don't think so because the resistors are already seem to be on the strip, and i connected it without any other resistors and it worked fine.

6) Heres is the picture of 3 leds on the strip: http://i.imgur.com/0G5L9
« Last Edit: February 25, 2011, 14:08:42 PM by HTF »

kam

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Re: LED strip dimming off circuit
« Reply #3 on: March 07, 2011, 09:29:33 AM »
sorry for the delay. trolls confused me and i failed to see your new message

watch this circuit:
http://pcbheaven.com/circuitpages/LED_Fade_In_Fade_Out_Dimmer/

and specifically the section "Need more current?"
I introduce a power transistor. This is something that you need to do as well. If you drive the LEDs directly with the small transistor, they will never be full bright.  So, you need this second stage with the BD243 to amplify the current.

Mungoo

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Re: LED strip dimming off circuit
« Reply #4 on: March 16, 2012, 09:11:57 AM »
hi! i need some help with the above tutorial. i like the circuit but i want when i push the push button the led turns on and stays on, and when i push it again the led turns off. i need a toggle push button. so please tell me what i must change in the program or a new program thanks

kam

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Re: LED strip dimming off circuit
« Reply #5 on: March 17, 2012, 09:40:38 AM »
hi! i need some help with the above tutorial. i like the circuit but i want when i push the push button the led turns on and stays on, and when i push it again the led turns off. i need a toggle push button. so please tell me what i must change in the program or a new program thanks

there is no "program" in the above circuit. but probably the resistor across the capacitor is either broken or too high.