Using Microcontrollers to Control Simple Machine Inventions.

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Even simple inventions often require some sort of control system.






Using Microcontrollers to Control Simple Machine Inventions

Microcontrollers For Controlling Simple Machine Inventions

Even simple inventions often require some sort of control system. It may be that a simple machine invention you have come up with requires several actions to perform its intended function.

Micro controllers are a great way to provide control for simple machines and even complex machines.  Microcontrollers are very small, very powerful, and inexpensive.  Micro controllers have an array of built in functions including microprocessors, voltage comparators, analog to digital converters, timers and more.

I've recently been seeing ads on TV for a new product that looked interesting, the Glade Sense & Spray motion activated air freshener. I think this product is a great example of a simple machine ripe for a microcontroller.  I did a Google patent search and found a patent application that for an air freshener device belonging to Johnson and Johnson that uses a circuit with a couple of IC chips for control of the device.  It can periodically spray air freshener or it can be manually activated.

Application number: 11/247,793
Publication number: US 2006/0076366 A1
Filing date: Oct 11, 2005

The patent application shows a motor and gears along with a lever to actuate a spray canister of aerosol fragrance.

Let's see how we could control such a simple machine, and automatic air freshener dispenser, with a microcontroller.

Microcontroller chips are made by a number of manufacturers and there are thousands of variations available.  MicroChip, the brand I use, has microcontrollers with from 6 pins to over 100 pins.  Two pins are always needed to supply power and ground, which leaves all the rest of the pins for inputs and outputs. 

I studied the MicroChip site, downloaded the free software and learned some rudimentary programming.  Then I bought a basic compiler so I could program in basic, which I find much easier than using the machine or assembly language.  You can purchase a programmer for the chips for less than a hundred bucks, and you can download everything you need free online to get into programming those little suckers.  There are forums online where the members jump right in to help newbies and experienced programmers alike.

For almost every project I've done, an 8 pin controller has been perfect.  To automate the automatic aerosol dispenser using an eight pin 12F675 microchip controller we would only need one pin for the output to drive. We will use a motor / actuator similar to the mechanism used by the Johnson & Johnson patent application.   That leaves us with 5 pins to use as inputs.  We could stay simple and connect a button for manual operation to one of the pins, a motion sensor to another pin, and two pins for switches to select the mode of operation.

Selecting which pins you use for what depends on  what is internally connected to the pin.  Usually any pin can be used for a general purpose input or output, but if you want to use some of the internal peripheral devices you have to use the correct pins to access them.

Using these inputs, we can have a switch to turn on or off motion detection, turn the timer function on or off, or accept an input from a motion detector, and output a signal to the motor and still have a pin left over.

Microcontrollers typically have a built in clock plenty accurate enough for this application. If you need highly accurate timing you can use a crystal to establish the clock frequency. 

Since we have an extra left over pin, we could hook it to a temperature sensor and add a little more complexity and intelligence to our air freshener dispenser.  We could program it to ignore the timer when the temperature is below 40 degrees figuring that there probably aren't any people smelling stuff in a room that is below 40 degrees.  Or maybe we could have it spray more frequently if the temperature is hot.

Or we could use the remaining unused pin for a light sensor and if the room is dark, then the dispenser won't spray.  Obviously we are getting a little carried away with our automatic air freshener device, but it allows us to explore what these microcontrollers can do.

We could switch to a chip with 12 or 14 pins and add a wireless receiver to the package for remote control of the dispenser as well.  We could use another output to trigger an audio alarm.  The chip could easily keep track of how many times it operates with it's internal counters and sound an audio signal when you run low on fragrance and the canister needs replacing.  You can use yet another pin to drive a LED. The led could blink when you begin to run low.

We still have pins so let's add a microphone and detect voices.  We can then write into the program that's stored in the chip to begin its timing sequence only after hearing someone's voice if the room has been dark for over an hour. 

The micro-controllers typically have memory for storing the program, which doesn't disappear when you power down the chip, and ram memory that does disappear when you remove power.  Many of these chips even have serial communications implemented internally to the chip like RS232, Ethernet, USB and the like.

Now that we have the worlds fanciest air freshener dispenser ever, why don't you study up on micro-controllers, and use one to control the next simple machine invention you create, or maybe even a complex machine or controlled process.


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