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Help with Wake up Light circuit (Alarm clock light)

A

Thread Starter

ABaruwal

Joined Jan 28, 2011
15
Im making a wake up light for my engineering project. This is basically like an alarm clock, however instead of creating sounds to wake you up, it lights up and simulate sunrise to wake you up naturally.
It will start lighting up 30 minutes before set time, from dim to gradually fully bright at the set time.

I've looked all over a internet for a circuit but unable to get any help.
I would really appericiate your help on building a circuit

Thank you
 
Wendy

Wendy

Joined Mar 24, 2008
23,429
A simple PWM circuit will do the dimming with a minimum of fuss.

LEDs, 555s, Flashers, and Light Chasers Chapter 5.

Generally SAD lights aren't used as wake up lights, though there is no reason not to do it this way. SAD lights are used during your active part of the day to stimulate your brain (hippocampus I believe).
 
A

Thread Starter

ABaruwal

Joined Jan 28, 2011
15
Bill_Marsden said:
A simple PWM circuit will do the dimming with a minimum of fuss.

LEDs, 555s, Flashers, and Light Chasers Chapter 5.

Generally SAD lights aren't used as wake up lights, though there is no reason not to do it this way. SAD lights are used during your active part of the day to stimulate your brain (hippocampus I believe).
Click to expand...
Thank you for you quick reply,
Im not considering on buying a Alarm clock kit and changing the output source to light by removing the buzzer.

Do you think it will work if i replace the buzzer with your PWM circuit??

Im a student and a beginner at electronics studying engineering at college.
Thank you
 
A

Thread Starter

ABaruwal

Joined Jan 28, 2011
15
Hello,
im new to building up circuits and need some serious help with my project :(

Im making a wake up light, This is basically like an alarm clock, however instead of creating sounds to wake you up, it lights up and simulate sunrise to wake you up naturally.
It will start lighting up 30 minutes before set time, from dim to gradually fully bright at the set time.

I want the LEDs to light up gradually, from dim to fully bright within the time of 30-60minutes. On a set time i want the LEDs to start lit up and then after 30-60mins be fully bright.

To trigger the time, im going to use a timer circuit (using an alarm clock kit) and possibly replace the buzzer with this circuit


Can somebody please help me with the circuit and give me advice on wheather it may work or not.
 
Bernard

Bernard

Joined Aug 7, 2008
5,784
If you did not like the PWM suggestion, might try a counter & digital to analog convertor for long time ramp up of light.
 
Wendy

Wendy

Joined Mar 24, 2008
23,429
Sorry I didn't get back with you, the post slid by me.

One of the ways that occurred to me was a counter controlling a PWM circuit. You connect the counter (something like a 4040) to a really simple D/A converter and use it to drive the PWM circuit.

Are you able to design from here, or are you needing schematics?

I'm going to assume you have two things, a stable power supply, and logic signal from the clock (a 1 or a 0) to turn the circuit on. From your description you don't care if it slowly turns off, just on.

The other approach is much simpler, and pure analog. A integrator feeding the PWM modulator. Thinking about it, this is probably the best approach, since precision isn't really needed. Still need the two requirements though.
 
bertus

bertus

Joined Apr 5, 2008
22,278
Hello,

I merged the two threads.
This may sometimes look a bit odd, but all information is now in this thread.

Bertus
 
Wendy

Wendy

Joined Mar 24, 2008
23,429
Speaking for myself I would rather design something like this with a minimum of help. I am willing to draw a schematic, but you need to tell me what level of detail you need.

At this point I assume you are mostly a beginner, but that is because I don't really have enough background about your technical background.
 
Bernard

Bernard

Joined Aug 7, 2008
5,784
How many LEDs need to be controlled? This question came up last year for an aquarium brighton- dim light.
Found old post: malaybiswas , but no final rpt.
 
Last edited:
A

Thread Starter

ABaruwal

Joined Jan 28, 2011
15
Bill_Marsden said:
Speaking for myself I would rather design something like this with a minimum of help. I am willing to draw a schematic, but you need to tell me what level of detail you need.

At this point I assume you are mostly a beginner, but that is because I don't really have enough background about your technical background.
Click to expand...

Thanks once again

i just want the circuit to turn on gradually from dim to fully bright within a time of anywhere between 30-60mins.
Its like an alarm clock so, it wouldnt matter how it turns off.
 
Last edited:
A

Thread Starter

ABaruwal

Joined Jan 28, 2011
15
Bernard said:
How many LEDs need to be controlled? This question came up last year for an aquarium brighton- dim light.
Found old post: malaybiswas , but no final rpt.
Click to expand...
5 bright LEDs
i was previously thinking of lighting up each LED every 8minutes
so after 40 minute all the LEDs will light.

But doing this will not result on gradual brightness..
 
Bernard

Bernard

Joined Aug 7, 2008
5,784
Maybe 3 strings of 3 LEDs each, total drain of 60mA? PWM- 100Ωs, darlington driver-40Ω each leg. If a step function is used, how large of a step would ba acceptable?
 
Wendy

Wendy

Joined Mar 24, 2008
23,429
Those superbrites are bright, but they aren't as bright as you think. They quote a spec of luminous intensity (instead of lumens) of 12000. I find them not using a SI number that is included on most light bulbs suspicious in the extreme. It is a trick used for marketing to make a product seem brighter than it actually is.

You want real intensity look for 1W or 3W LEDs. They use more current, a 1W uses 700ma (0.7A) instead of 20ma, they are proportionally much brighter. Indeed, they may be way too bright, as they compare with standard light bulbs. One 1W LED will outshine 9 conventionals by a large margin.

I don't believe 9 conventional LEDs will even come close to being enough though. Think 16, 25, or 36 (notice they are square products?). How big in square were you wanting this panel to be (that is the normal SAD box convention). You can get sheets of pexiglas defusers from the hardware store, as you do not want to look at bare LEDs directly, doing so too close can cause eye damage.

I said I would draw a schematic, so I will. It will drive either set of LEDs easily.

I'm still waiting for a DC power supply voltage. You will need several amps if going for really high intensity, 1 A if going for conventional LEDs (and it will be much dimmer).

My preference is 24V, but I can use 12VDC. The more DC voltage the less amps. If you go with 1W LEDs we'll negotiate the power supply vs. quantity of LEDs. The conventional LEDs are easier to work with, by a lot.
 
A

Thread Starter

ABaruwal

Joined Jan 28, 2011
15
Bill_Marsden said:
Those superbrites are bright, but they aren't as bright as you think. They quote a spec of luminous intensity (instead of lumens) of 12000. I find them not using a SI number that is included on most light bulbs suspicious in the extreme. It is a trick used for marketing to make a product seem brighter than it actually is.

You want real intensity look for 1W or 3W LEDs. They use more current, a 1W uses 700ma (0.7A) instead of 20ma, they are proportionally much brighter. Indeed, they may be way too bright, as they compare with standard light bulbs. One 1W LED will outshine 9 conventionals by a large margin.

I don't believe 9 conventional LEDs will even come close to being enough though. Think 16, 25, or 36 (notice they are square products?). How big in square were you wanting this panel to be (that is the normal SAD box convention). You can get sheets of pexiglas defusers from the hardware store, as you do not want to look at bare LEDs directly, doing so too close can cause eye damage.

I said I would draw a schematic, so I will. It will drive either set of LEDs easily.

I'm still waiting for a DC power supply voltage. You will need several amps if going for really high intensity, 1 A if going for conventional LEDs (and it will be much dimmer).

My preference is 24V, but I can use 12VDC. The more DC voltage the less amps. If you go with 1W LEDs we'll negotiate the power supply vs. quantity of LEDs. The conventional LEDs are easier to work with, by a lot.
Click to expand...
I think conventional LEDs with 12VDC would be good enough for my project. As part of my poject is to put the cost down aswell.
 
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