Count is a simple, yet useful, application that helps you perform the tedious task of counting. Count! allows you to easily count large volumes of items without ever losing count. Best of all is that count’s shake-to-count feature allows you to count anything with a flick of the wrist. Count! can have any number of uses from counting the number of people in a room to doing inventory. And for Baseball enthusiasts Count! includes a ball and strike counter. Count even includes a pedometer to count your steps. Count has an endless number of uses.

Features:

- Normal counter allows you to count forever

- People counter allows you to set a maximum count

- Strike counter allows you to count balls, strikes and pitches

-Pedometer mode allows you to use your iPhone as a pedometer

- Shake to count feature allows you to simply shake your iPhone to count

Sadly I didn’t take any pictures but I did get to see some amazing stuff. I went on a friday which happens to be show-and-tell day were anyone who’s working on a cool new project can show it off. I saw a new 3-d models of the building for robot navigation, a GUI that visualizes all the data from the sensors on the robot, and new sensor optimization code to help align the data from the different sensors. It was a really great visit and I hope to see more stuff coming from them  in the near future.

Features:

- Normal counter allows you to count forever

- People counter allows you to set a maximum count

- Strike counter allows you to count balls, strikes and pitches

- Shake to count feature allows you to simply shake your iPhone to count

After I finished up on my photo-resistor stuff last night I was thinking, there is so much more potential for stuff than just that little white to black color background. So I decided I would make and RGB color mixer.

I grabbed 2 more photo-resistor and hooked them up as voltage dividers with 4.7K ohm resistors ( I didn’t have any 5k). I made a quick edit to my photoresistor app to make it read analog pins 3, 4, and 5 and assign them to blue green and red, respectively. The edit looks like this (the full app is available for download here):

  background(theBackground);

  val1= arduino.analogRead(5);

  val2= arduino.analogRead(4);

  val3= arduino.analogRead(3);

  theBackground= color(val1, val2, val3);

Where val1 is red val2 is green and val3 is blue.

This is the final result:

Feedback is not only welcome but much appreciated. I’m thinking of making some kind of project out of this I’m just not sure what yet. If you have any ideas please leave a comment.

When I got home I decided to play around with them. I decided that it would be cool to have a potentiometer that adjusts based on light so I grabbed one of the larger photo-resistors to test out its resistance with my multimeter, what I found is that the resistance varies from about 70 ohms in very bright light, to about 200K ohms in a very dark environment. So I decided to go with about 10K ohms as the second resistor, this means that in a fairly averagely lit room (which causes a resistance of about 7-10k ohms on the photo-resistor) you will get a reading of around 2.5v (assuming your using a 5v source). As it gets darker that value will go up (this actually depends on the configuration of your voltage-divider circuit if you have the 10K reistor connetcted to 5v with the photo-resistor connected to GND this will be true if not it will be reversed, light will make the value go up dark will make it go down) and as it gets lighter the value will go down.

Now what I have said here requires some knowledge of how a voltage divider (or potentiometer). A voltage divider is essentially just 2 resistors wired in series and a test point between them. The voltage is then divided based on the ratio of the value of the resistors. For example: if I have a 5v source with a voltage divider consisting of a 10K and 5K resistor like this:

A simple voltage divider

This would read a voltage of 1.666666V. Why? Because 5/15(sum of resistor values)=.3333333. That means that .33333333 = 1K on a resistor. since the resistor we’re reading is 5K ohms we need to multiply .33333*5=1.666666. This same thing could be achieved with a 2K and 1K resistor (5/3=1.666666) because the ratio is still the same 5/10=1/2.

The the photo-resistor circuit works by varying one of the resistance values so when its light and the resistance of the photo-resistor equals about 5K we get the same result as above but when it gets darker and the resistance increases to 10K we get a reading of 2.5 volts because 10/10=1/1 and 5/2=2.5. 

I mentioned above that if we switched the resistors around we would get an increase in voltage under light and a decrease in dark. Why is this? It is because if we read the voltage across the 10K resistor rather than the photo-resistor, than as the resistance of the photo-resistor drops below 10K under light we get an increase in voltage because 10/5=2/1 and so we would get 3.33333 rather than 1.666666. An increase from 2.5 volts rather than a decrease.

Now that we understand how potentiometers work lets continue. As I was thinking of what I could do with this I decide on the simplest thing. I already had an app that displayed the value of a potentiometer, so why not just start with that(you can view the post for the Potentiometer App here and download the source code here). Below is a video of it in action.

But this didn’t really seem to make sense to me. Why display light as a circle, it make sense when you are turning a nob but not when you are measuring light. So I decide to make a simple app that changes background color based on the value of the resistor. The only problem with this was that the screen got lighter as the photo-resistor got darker so I flipped around the circuit and this is the result:

The source code is available here.

Below is a photo of my arduino with the Pot hooked up

The source code is available here.

Here is a video of the app in action