# Combining a light therapy LED lamp with a light alarm clock - programmable dimmer

I live in a place where there is little daylight in winter, so I would like to use a light therapy lamp. Also, I would like to use it to wake me up, gradually increasing the intensity of the light over a preset time, starting at a preset time. There exist light alarm clocks that do just this, but they are way darker than a light therapy clock, so I would like to combine those two functionalities.

My idea is to buy a simple light therapy lamp that is on/off only and create some kind of controller circuit that varies input voltage according to my settings, possibly with a mini-computer to get the alarm clock functionality.

The features I would like to have:

• a gradual increase of light intensity (doesn't need to be smooth, 5 steps or something like this are fine as well)
• some kind of control buttons so I can turn the alarm/the light on and off as well as change the alarm time (it is okay for me to use my computer to change more advanced settings, but I would like to be able to do these ones directly)
• ideally some kind of display/led combination to show me alarm time
• as little as possible stand-by energy consumption
• as cheap as possible
• not overly complex - I have little experience in electronics and would still like to understand and build the circuit. I have some knowledge in programming and feel comfortable to implement an alarm clock software in an Arduino/Pi etc.

I know that some of the features could be mutually exclusive. It's just to give you an idea of what I am looking for. The most complicated part for me is to figure out if and how I can dim the lamp, since I do not know how to do that.

This is an example for the lamp I might buy. The power specs for this lamp seem to be input 100–240 V ~ 50/60 Hz, and the output is 12 V DC, 650 mA. It seems to me that the power supply is external, i.e. it has a externally available 12 V DC input, but I don't know that. If it's possible to work with the 230 V input that would be best.

How can I dim the LED lamp in a programmed way? What do you suggest to control the dimmer as an alarm clock?

• What exactly is your question? – Elliot Alderson Jan 19 at 13:37
• @ElliotAlderson You are right, this kind of got lost in the process of writing this question. I edited the question to clarify it. My main problem is that I do not know how I could dim the lamp, I hope I can work out the rest. – Paul Paulsen Jan 19 at 13:43
• Your question is really too broad for this site, and we can't know how to dim the lamp without more technical information about how the lamp works. You should just buy a product that does what you want. Sorry, voting to close. – Elliot Alderson Jan 19 at 13:46
• A serial DAC or S/W controlled Vavg using PWM can accomplish this function with suitable LED drivers and Luminaire. Very bright 4ft Fluorescent tubes with a quad 1 wire + common ballast for 4 tubes, around perimeter of wall (valence) can give bright yet diffused soft indirect light, add as many as needed. Glare is an annoyance. – Sunnyskyguy EE75 Jan 19 at 16:30
• That means once you figured out how power is supplied to the LED lamps in the SAD luminaire, you can then use a µC to control how that power is supplied, for example, with a timer or whatever you like to program the SAD luminaire to do over time. – Systembolaget Feb 8 at 11:59

In general terms, and considering your electronics knowledge and software requirements, I would suggest to use a RasberryPi, which will allow you to do the dimming by controlling a PWM GPIO.

The big question is if the lamp you have chosen is dimmable. The most likely answer is no, as it will already have an internal LED driver, and therefore the results could be unpredictable. With some luck and knowledge, you might find that the driver used has the possibility to be driven on PWM, but without seen it, and finding the documentation for it, I see that as a quite unlikely feat. In addition to that, you will still have the issue of interfacing the RaspberryPi with the LED panel, first of all because of the different voltage levels, that you are likely to find.

If I was to do it, yes, I would say it is possible, but without a good understanding of the electronics that goes on inside the lamp, it becomes an impossible task.

I do however wish you good luck, maybe you can find a friend who is into electronics, and is willing to help you out.

Your best bet would be to use a Phillips HUE smart bulb. No need to reinvent the wheel.

The HUE would be easier, less expensive, and very likely better than a DIY solution.
The HUE exceeds your wish list of features.
For example you can use Alexa to use voice commands to turn on, off, and dim each individual bulb. "Alexa, dim bedroom to 50%"

Phillips understands LEDs.

UPDATE

Sorry, but it seems like you didn't read my question well. There also exist various light alarm clocks (which will do the job way better than the HUE), but they are all not as bright as I would like my lamp to be - 10.000 lux is recommended for a light therapy lamp. The HUE has about 50 at the same distance (10cm).

Yes I did read your question. Obvious to me you do not understand Lux. For someone to say a light bulb can only provide 50 lux at 10 cm can only imply that person does not understand lux.

There are many HUE smart bulbs. I highly doubt any of them will only illuminate a surface at 50 lx. The Difference Between All of Philips’ Hue Light Bulbs

Not sure where you got the 50 lux figure for the HUE but it is very unlikely that it would be only 50 lux @ 10 cm. 10,000 lux is an ambiguous number without surface area or steradian being specified. A 750 lumen "HUE Lux" smart bulb would give you more than 10,000 lux at 10 cm because the the HUE Lux is an anisotropic source and not an isotropic source which would yield far less lux. Lumen is a spherical isotropic measurement. Lux is a measurement of the intensity of the light illuminating a surface.

1 lx = 1 lm/m²
At a distance of 10 cm the surface are would illuminate a surface area of about 250 cm².
1 lm focused on a 250 cm² surface would be about 40 lux (10,000/250).
750 lm would give you 30,000 lx

create some kind of controller circuit that varies input voltage according to my settings

This is not possible. It is nonsensical. If you could create a controller to alter the "current" (not voltage), it certainly would not be a practical thing to do. We don't even know how the LEDs are powered. A 12V, 650 mA power supply is not an indicator of the LEDs voltage or how they get their current.

My main problem is that I do not know how I could dim the lamp,

Not likely a knowledgeable person could.

I doubt you understand light therapy. You indicated you wanted to purchase a lamp for SAD therapy. This is very different from a "wake up" light. Do you know how bright 10,000 lux is? Moonlight, from a full moon on a clear night is about 0.25 lux.

The sun is about 120,000 lux and you will go blind looking at it.

The light at sunset on an overcast evening will illuminate at about 50 lux.

Looking into a HUE Lux smart bulb at 10 cm will be very very uncomfortable and may cause permanent damage after starting into it for 30 minutes.

Have you been diagnosed with SAD? Did a doctor prescribe 10,000 lux. 10.000 lux is the maximum illumination that should be used, not the recommended. Once diagnosed a doctor prescribes the lux and duration.

Clock wake up lights are not used for SAD light therapy. The Phillips "Wake Up" light is 300 lux with 20 brightness settings and has nothing to do with SAD light therapy.

• Sorry, but it seems like you didn't read my question well. There also exist various light alarm clocks (which will do the job way better than the HUE), but they are all not as bright as I would like my lamp to be - 10.000 lux is recommended for a light therapy lamp. The HUE has about 50 at the same distance (10cm). – Paul Paulsen Jan 22 at 7:05
• WHAT????? See my update. – Misunderstood Jan 22 at 20:48
• First of all, thank you for taking all the time to write all this, even though I do not appreciate the tone it is written in - this might be in answer to my accusation that you didn't read my question well and therefore my fault. I am sorry about this. I want to use a single lamp for light therapy and for wake up, because then I only have to buy one lamp. Many people buy a very bright lamp and not use it from 10 cm, but further away and without staring directly into it, which can be a good compromise. I experienced a light therapy lamp in a setting like this and it helped me wake up a lot. – Paul Paulsen Jan 22 at 23:03
• I am very well aware that the Wake Up lights available do have nothing to do with SAD light therapy - this is the reason why I asked the question, I want to have something that can both. Seems like the answer is that it's not possible, which is fine, but no reason to get angry at me. However, you are right that I mixed up my calculations for the estimate of the lux of the lamp in quite an embarrassing way. It seems that the HUE lights are a lot brighter than I thought and I will consider getting one of those. Thank you for your answer. – Paul Paulsen Jan 22 at 23:15
• My emotions (or lack there of) are often misunderstood, that is what I picked the name. My only interest is to present factual information. I do not expect others to understand the technical intricacies of intensity, radiance, illumination and optical geometry. – Misunderstood Jan 23 at 0:02