Saturday, July 28, 2007

Fun science

Without further ado:

Lemon battery

The movie shows how to turn a lemon into a battery, used to power a LED or pocket calculator.

Electric motor shows you how to build a very simple electric motor using only a battery, a magnet and a drywall screw. The movie shows the screw spinning.

Email subscribers: Visit online version to view the movies.

Tuesday, July 24, 2007

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Sunday, July 08, 2007

Home Automation

After we moved to our new apartment, I quickly discovered the limitations of the existing hard-wired circuit. First of all I didn’t have any possibility to control the overhead lights in any of the two bedrooms from the installed wall switches. Turning on the Christmas lights was a real pain also – I had to crawl under the tree braches almost 4 feet in order to plug the lights.

Home automation is an old passion of mine which I rediscovered recently after a routine visit to a local RadioShack store. For only $20 I purchased a Plug ‘n Power – Home Automation Kit which on sale. I bought the kit on impulse without actually knowing that under the hood is using a very popular technology X10.

The kit offered me only the chance to play with this automation technology, without solving much of my problems. Luckily, had an end-of-the-month sale (their entire strategy consists in sales) at which I purchased a couple of other X10 modules: the screw-in lamp modules, the wall-switches and transceiver module (the motion sensor and remote chime were just included in the price).

Click to enlarge

The setup

I screwed in the screw-in lamp modules in the overhead light fixtures from the two bedrooms and configured the wall-switches to control the corresponding lights. I also plan to use the RadioShack lamp/ appliance module during this Christmas season. For the moment I’m using the remote chime module as a wake-up device (controlled by RadioShack’s mini controller). As for the motion sensor I’ll probably integrate it in the security system.

Other scenarios

When they are talking about automation, almost everybody try to look futuristic. They talk about the advantages of turning on and off appliances according to a predefined schedule or about executing an entire sequence of macros at a touch of a button. While nice, these scenarios don’t actually apply today. The site at describes three down-to-earth X10 scenarios such as: outbuilding lights, coupling room lights and convenience switching.

X10 or not-X10

X10 is a nice technology which helps you connect controllers and modules in a flexible network without changing the hard-wired circuit:

- X10 is cheap comparative with other home automation technologies
- X10 is standard: as you can see I’ve seamlessly integrated modules coming from two producers
- X10 is a 25 years old technology. This brings several disadvantages:
- slow (it takes ¾ seconds from the moment you press the switch until the lights turns on)
- commands may collapse
- no command acknowledge (if you send an ON command the only way to see if the command was executed is to inspect the appliance. This may be easy with a light bulb but more complicated with a slow device like your water boiler.)
- not secure (your neighbor may be able to control your devices)
If you are willing to pay 4 – 5 times more, other technologies, some backwards compatible with X10 are there for you.