An Inexpensive Dawn Simulator

A Dawn Simulator for under $100


You don't have to suffer from Seasonal Affective Disorder (SAD) to enjoy a Dawn Simulator. Up here in Seattle, the sun rises at about 8AM in the middle of winter, far later than the required wake-up time for most of us during the week. A dawn simulator eases the shock of waking up in the darkness by slowly turning on the lights to simulate the gradual brightening of the dawn.

Unfortunately, commercially advertised dawn simulators tend to cost hundreds of dollars, making them unacceptably expensive for many people. But if you have your own computer (or just access to one), here's a way you can have a dawn simulator for less than $100, complete.

The key to the system is X10 technology. X10 is a home automation system designed to allow you to remotely control and automate everything in your home, from lights to stereo. Switch modules send simple command signals over the power lines to appliance and lamp modules, which turn on, turn off, or dim the lamp. You just plug the switch module into one outlet, plug the lamp module into another outlet, set the address switches to match, and you've got a remote dimmer switch.


For the dawn simulator, I used the following components (prices from 1999):
MT522 mini-timer (functionally equivalent to MT10 mini-timer) $19.11
PLM03 (LM465) lamp module with dimming capability $10.35
CM11A computer controller $39.45
(shipping for the above items) $5.81
300 watt halogen torchier lamp $15.19
Total cost:$89.91
I purchased the X10 components via mail-order from Worthington Distributors, 800-282-8864. (See also the price list mentioned in the Resources section below.) The 300-watt lamp came from a local hardware store (in this case, Eagle Hardware), $13.99 plus tax.

If you are planning on leaving your computer on all the time, you may be able to use the CM17A "Firecracker" instead of the CM11A.

Functional Outline

Here's the general way the system works:

If you're really on a tight budget, you could skip the MT522 and program the CM11A to start the dawn simulation at the desired time. The MT522 adds the convenience of being able to easily enable or disable or change the time of the dawn simulation from your bedside. It also provides direct on/off switches for your lamp.

The PLM03 lamp module does not have the ability to turn on at a specific brightness; if you send it the ON command, it comes on at full brightness. There is a new lamp module, the LM14, which has this ability, but it costs about $27. I use this simple trick (suggested by tech support at Worthington) with the PLM03: instead of sending it an OFF command to turn it off, send it a series of 16 DIM commands, which will dim it down to zero, effectively turning it off. The next morning when the dawn simulation begins, simply start sending BRIGHTEN commands without ever sending an ON command. The CM11A can be programmed to receive the OFF command from any control module (such as the mini-timer, which has switches on the top) and convert it to a series of DIM commands for the PLM03.


There are four ON/OFF switches on the mini-timer, normally allowing you to control up to four devices. You can program the timer to turn each device on or off twice each day; that's a total of 16 times that can be programmed into the timer. There is also a buzzer (well, they call it a buzzer, but I'd call it a beeper), which goes off whenever the timer sends an ON signal to device 1. You can disable the buzzer (it has it's own switch), and you can disable the timer for device 1 (by setting the clock to set-time mode; but the timers for devices 2 to 4 still operate). These two switches allow you to control what happens at the ON time for device 1:

Unfortunately, there are not separate enable/disable switches for devices 2 through 4.


There are two possible scenarios:

  1. You have a separate alarm clock, and are using the mini-timer only to control the dawn simulation.
  2. You are using the buzzer on the mini-timer as your alarm clock.
For the first scenario, set the house code on the mini-timer to A and the 1-4/5-8 switch to 1-4. The four switches on the mini-timer now send ON and OFF signals to devices A1 to A4. Set the lamp module to address B1. Program the CM11A to use A1 ON/OFF and A2 ON/OFF to start macros that send DIM or BRIGHTEN commands to B1. Switch 1 on the mini-timer is used to start the dawn or dusk simulation. Switch 2 on the mini-timer is used to turn the dawn lamp fully on or off immediately. Pushing switch 1 on sends an A1 ON signal; this triggers the CM11A to begin the macro to gradually brighten B1. Similarly, pushing switch 1 off sends an A1 OFF signal, which triggers the CM11A to begin the macro to gradually dim B1. You can program your dawn start time as the ON time for switch 1, and you can program your dusk time as the OFF time for switch 1. Or, you can leave the dusk time unprogrammed, and just push the switch 1 off button when you climb into bed. The light will then slowly dim starting at that time. To turn the lamp fully on or off, push switch 2 on or off. This triggers the CM11A to send out a series of commands to device B1 (the lamp) to fully DIM or BRIGHTEN it. Remember that we never send an OFF signal to B1, since then we would not be able to gradually brighten it the next morning. Thus we use the CM11A to translate the "instant on/off" commands to BRIGHTEN/DIM commands. Switches 3 and 4 on the mini-timer are not needed for the dawn simulator, so can be used for anything else.

The second scenario, in which you want to use the buzzer on the mini-timer, is slightly more complicated. It is similar to the first scenario in that we use the CM11A to convert ON/OFF signals to BRIGHTEN/DIM signals so that we never actually turn the lamp module off. The addresses on the mini-timer and the lamp module are set the same way, but the switches on the mini-timer are used differently. In this scenario, switch 1 is used to control the buzzer time, switch 2 is used to start the dawn or dusk simulation (which was done by switch 1 in the previous scenario), switch 3 is used for instant on/off (which was done by switch 2 in the previous scenario). The programming in the CM11A is modified accordingly.

In the second scenario, we can choose one of the following approaches for enabling and disabling the dawn simulation:


If you are using a PC, you can download the ActiveHome software from X10 for free. See the Resources section for additional pointers.

If you are running Linux or Unix, you can try using a program called cm11 written by Erik Olson, placed into the public domain in February, 2003.

The new Java Comm API will make it possible to write X10 control programs using Java (they demonstrated exactly that at JavaOne '98 in March 1998).



You can easily and inexpensively add incremental improvements to this system.

Want more light for your "sun"? Add another lamp module and another 300 watt lamp, set to the same address as the first module; total cost under $30.00. You could even put them in different rooms if you have more than one person to wake at the same time.

Want to set up a second dawn time in another room? Buy another lamp module and lamp, set them to another address, and program the CM11A with another set of macros for the second lamp. For maximum flexibility controlling the second lamp, buy another mini-timer; total cost under $50 for an entire second dawn simulator.


For more information on X10 technology, see the X10 home page.

Sometimes offers special deals on the Firecracker.

The discussion group for home automation is comp.home.automation

For a list of X10 distributors along with a price comparison, see Bill McFadden's X10 Mail-order Survey

The X10 FAQ answers questions about X10. Another is the Hometeam X10 FAQ (parts A to F).

X10 has an on-line Manual for the MT10A in Adobe Acrobat format. The Acrobat reader is free; you can use it to print a copy of the manual to your printer.

X10 also has an Acrobat-formatted Manual for CK11A, their ActiveHome bundle that includes the CM11A.

Free software for the CM11:

There are also commercial packages available, but you'll have to do your own searches if you're interested in that.

For more information on Seasonal Affective Disorder, see

or look up the phrase in your favorite search engine for thousands of hits.
jimmc   Updated February 17, 2003   Originally posted April 1999