Questions about Microprocessors for sensors and control devices

[Erich_870]

Hey guys,

Can anyone help me with a project dealing with microprocessors and building some sensors and controls for my home? It could be websites, books, how too's, or even better, direct assistance :bowdown:

I've always wanted to take a course on microprocessors just for my own benefit and use in crazy project ideas, but I never found the time. So hopefully there are a couple resident hardware geeks around :thumbup: (I'm a civil geek :spit:)

Here's my first project idea that I need some assistance with.

My home has the oil fired boiler and cloths dryer in the garage. Both of these vent to the outside, thus requiring "make up air" when they operate. Currently they pull air through gaps around the garage door and other "leaky" spots.

I'll soon be starting a thorough weatherization project that will fill all these gaps. In order to allow both of these appliances to operate at peak efficiency (and prevent possible malfunctions) I need to allow make up air in the garage. I want to build a system that opens a damper in the wall, allowing fresh air in when either the dryer or boiler is running.

I figure I'd use an electronic eye on the boiler and a pressure sensor on the dryer to trigger a servo to open the damper. I have the damper I want to use, and I'll post a pic when I get home.

How would you go about designing this system?

Thanks,

Erich

[DHC6twinotter]

Not sure if this would work for your application, but here's an idea:

To prevent the risk of a hose failure on washing machines, a few companies have developed an "automatic water valve" (sorry, I forget the real name). The valve is placed between the pipe and the hose, with the hose being the most common point of failure. The automatic water valve is then plugged into an electrical outlet, with the washing machine being plugged into the water valve. When the washing machine is turned on, the water valve senses the increase in current, and turns on the water valve. When the machine turns off, the reduction in current flow turns off the water valve.

Anyways, with that being said, could you use some sort of current sensor on the boiler and clothes dryer? When it senses a current for either device, it could trigger the servo motor on your damper.

Just a thought. :hillbill:

[DHC6twinotter]

Also, Crestron and Extron both make good stuff if you plan on doing a lot of home automation. They might be overkill for just a dryer and boiler, but if you plan on adding more stuff in the future, they might be worth looking into. You may be able to run a central processor, such as the Crestron CP2-E or maybe even one of the smaller processors like the QMRMC will work for what you want to do. Extron makes good video switches and that sort of thing. There is also a company called X10 that makes some cheaper devices, but I have no experience with them. We used the Crestron CP2-E processor for most of our projects, with the processor controlling things like TVs, Projectors, Screens, DVD/VCR players, blinds, etc. Good stuff.

http://www.crestron.com/

http://www.extron.com/

Crestron does make a current sensor, but it's only good for up to 10amps. You may have to look elsewhere for a current sensor. I would image you would need at least a 30amp sensor for the dryer, and whatever you need for the boiler.

Anyways, just a few more thoughts based on my limited understanding. :hillbill:

[Erich_870]

Also, Crestron and Extron both make good stuff if you plan on doing a lot of home automation. They might be overkill for just a dryer and boiler, but if you plan on adding more stuff in the future, they might be worth looking into. You may be able to run a central processor, such as the Crestron CP2-E or maybe even one of the smaller processors like the QMRMC will work for what you want to do. Extron makes good video switches and that sort of thing. There is also a company called X10 that makes some cheaper devices, but I have no experience with them. We used the Crestron CP2-E processor for most of our projects, with the processor controlling things like TVs, Projectors, Screens, DVD/VCR players, blinds, etc. Good stuff.

http://www.crestron.com/

http://www.extron.com/

Crestron does make a current sensor, but it's only good for up to 10amps. You may have to look elsewhere for a current sensor. I would image you would need at least a 30amp sensor for the dryer, and whatever you need for the boiler.

Anyways, just a few more thoughts based on my limited understanding. :hillbill:


A current sensor is one way to go, but I don't know what it would take to find a sensor that could handle the current of a dryer.

I have the perfect spot to mount a photocell like this for the boiler
http://www.jameco.com/Jameco/Products/ProdImag/120299.jpg

and then a pressure stich like this in the exhaust hose of the dryer
http://www.allelectronics.com/mas_assets/image_cache/image_product.height.500;width.500;modified.120785 6799.PSW-12.jpg

What I'm wondering is how to make them control a servo to open the damper.

Erich

[slomatt]

Since both appliances generate heat it might be easiest to set them up with a thermocouple or other sensor that generates a variable voltage based on temperature and then set up a voltage comparator so you can generate a logical "high" signal when the threshold temperate is exceeded. You would then feed that signal to a relay to keep the vent open.

Here are a bunch of temperature related circuits.

http://www.educypedia.be/electronics/circuitssensortemp.htm

Using a relay to keep the vent open while the temperature is above the threshold would be the easiest. The more complex option would be to setup the system to keep the vent open for a given amount of time after the appliance is turned off.

- Matt

[Erich_870]

Since both appliances generate heat it might be easiest to set them up with a thermocouple or other sensor that generates a variable voltage based on temperature and then set up a voltage comparator so you can generate a logical "high" signal when the threshold temperate is exceeded. You would then feed that signal to a relay to keep the vent open.

Here are a bunch of temperature related circuits.

http://www.educypedia.be/electronics/circuitssensortemp.htm

Using a relay to keep the vent open while the temperature is above the threshold would be the easiest. The more complex option would be to setup the system to keep the vent open for a given amount of time after the appliance is turned off.

- Matt


cool, I'll check out all of the different circuits.

The one thing about the thermocouples is the dryer takes a couple minutes to warm up. I figured the pressure sensor would kick in right away.

Erich

[arjan]

2 simple temperature switches in the stacks of either oil burning appliance can be used to switch the baffle directly. That would be the most reliable way imo.
http://www.directindustry.com/prod/allen-bradley/temperature-switch-5071-58037.html
http://img.directindustry.com/images_di/photo-p/temperature-switch-58037.jpg

As for current sensing: greystone is your friend. They make very reliable and affordable current transmitters (0-10V out) or current switches. If you want to measure a lower current, you just loop it a couple of times through the hole.
http://www.greystoneenergy.com/English/products/power/products_high_current.html
http://www.greystoneenergy.com/English/gifs/SolidCoreAnimation.JPG

I work in the automation field, this sort of stuff I deal with all the time.