Micromouse Sensors

Posted on Feb 6, 2014

Ok, its been a while since I did much more than think about my micromouse, but over the last week or so I actually did some work` on the sensor design First off this is all theoretical, I need some bits an pieces before I can test this outside of simulation. Hopefully in the next week or so I will order the bits I need. Commonly optical sensors

Micromouse Sensors
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are used which act upon the basic premise that the diameter of a cone of light will get bigger as it travels, hence the intensity of light over a specific sensing area will vary with the distance the light has traveled. There are also other factors such as scattering and the reflectivity of the surface etc. etc. but there is a correlation, that`s the main point. I am concerned with detecting the intensity of the light reflected, and removing any noise. My current design assumes that I have a source transmitting IR light at 10KHz and a receiver which converts received light to a current (such as a phototransistor). First I convert this current to a usable voltage, then filter it to remove the noise and then I use a peak detect and hold circuit to get the sensor reading. This stage is quite simple, it takes the current and produces a voltage following the rule Vout = -Iin * R. The value of the resistor should be selected based on the current expected. I chose 66K as I am considering having some digital potentiometers in there, and that`s there value. Notice that the positive terminal of the opamp is connected to Vcc, this creates a virtual ground at Vcc allowing it to go from 5V down the 0V. Because of this the voltage is now upside down` so the next bit of the circuit fixes this. This is a difference amplifier which takes Vcc and subtracts out voltage from it, meaning the signal goes from 0V to 5V. Although not shown here...

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