MindStorms Projects:

 My official Mindstorms projects and be found at the AudreyMike Laboratory or MrSensor Laboratory.

 Trip Recorder uses the data logging features of the RCX.

 Sun Tracker follows the sun using my differential light sensor.

 PhotoBot is from the challenge on the Mindstorms page.

 Chart Recorder a simple way to plot conditions over time.

 Remote Control Button Pushers allows the RCX to control the world.

 Vehicle with Power Steering another way to steer a vehicle.

 The Mill a LEGO Crazy Action Contraptions Invention.

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The Trip Recorder

I wanted to measure the relative efficiency of the various ways I have to get to work. My measure of efficiency is how often and for how long the brake lights are on. More or longer braking time is considered poor efficiency and long stretches of no braking is good efficiency.

To see the brake light, I took a 64 strand fiber optic cable purchased from Edmund Scientific and pushed it into the hole of the dark gray connector peg. It just fits. Then using a 2x1 block with a hole, mounted the cable so that the light would directly strike the photodetector of the Light sensor. The other end of the cable was situated so that the light from the rear window brake light would shine into it. Every time the brake is pushed the Light sensor reading goes to over 60.

Before recording a trip, the RCX must see a SetDatalog command. This is an immediate command sent from a Visual Basic program. I usually set it to 400, which is more than enough.

The logging program is relatively simple. Apart from the usual housekeeping, it keeps looping waiting for the Light reading to exceed 60. When it does, it logs the value of a timer with the DatalogNext function. Timers have a 0.1 second resolution while the Watch is in hours and minutes. Then, when the light drops back below 60, it logs the duration of the event with the same function.

When the trip is over, the data is uploaded using the UploadDatalog function. If the total amount of logged data exceeds 50 you have to use multiple calls to this function. The data is then analyzed and plotted using Excel.

The photo shows how the fiber optic cable was attached to the Light sensor and a plot of the braking events logged during a trip to the store.

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Sun Tracker

The Sun Tracker always points toward the brightest point in the sky. It uses a Differential Light Sensor that I made myself from parts you can find at Radio Shack. This sensor sends the difference in light level between two photocells to the RCX. When the level is nearly equal the RCX reads 50, when it is all to the left it reads 0, and all to the right is 100.

The way the Sun Tracker works is very simple. As the sun moves across the sky, one of the two light sensors will fall into the shadow of the green nose like plate. When the RCX sees the light level imbalance, it turns the motor until the level in both sensors is nearly equal again.

click on photo to enlarge

The PhotoBot

This Robot is our take on the PhotoBot Mission. It follows the edge of a strip of printing calculator paper until it reaches a black strip at the end. There it stops, takes a photograph, spins around and follows the paper back to the start. Photo shows close-up of the trigger mechanism and a self-portrait.

click on photo to enlarge

Chart Recorder

This is a simple chart recorder. It writes a line on a strip of calculator paper that is propelled by a tire. The tire is geared down over 100 to 1 from a motor that runs at the slowest speed. A line is drawn by a pen that is moved back and forth with a second motor that has an 8 tooth gear running on a rack. A rotation sensor that also has an 8 tooth gear rides on the same rack providing feedback for the pen position.

An application of its use is illustrated in the photograph. The amount of light seen by a light sensor is used to position the pen. This gives a chart over time of the light level of a room or out of a window. A version of the chart recorder could be built that rides around on a mobile robot charting temperature, light level or other environmental variable. Programming the chart recorder requires more that the standard RCX language. I used Visual Basic to download commands to the RCX through the Spirit.OCX. I'm sure NQC or Mind Control could be used to do the same thing.

click on photo to enlarge

Remote Control Button Pushers

This is a device to operate two push buttons on a remote control. The version in the picture was designed to push the ON/OFF button and the channel-up button on a TV remote. The details of the pushing mechanism can be seen in the lower part of the picture. It could be used to operate remote controls for lights, tape recorders and alike. A surveillance robot could push the REDIAL button on a phone and PLAY on a tape deck to call somebody to report a break-in.

It uses two linear motion generators loosely based on designs from Leo Lego. When the motor runs forward it causes one side to advance and the other to retract. A touch switch is used to detect the motion and prevent the motor from going too far. Operation consists of running the motor forward or backward (depending on which button is to be pressed) until the touch switch reads 0 then reversing the motor until the switch reads 1 again to restore the linear motion generator to its neutral position. Some additional overshoot time may need to be added to insure the remote's button is fully pressed.

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Here is simple mechanical interface to push the buttons on a Radio Shack keychain remote (61-2663). This type of remote system allows you to control lights, appliances or practically anything that runs off house current. Keep the motor power to the minimum and only turn it on for 0.3 seconds in the one direction and then reverse for 0.2 seconds to bring it back to the neutral position.

click on photo to enlarge

Vehicle with Power Steering

Here is a basic vehicle that uses one motor to provide propulsion and a second motor to drive a steering mechanism. Short pulses to the steering motor will make the vehicle wander around randomly. When the vehicle is stopped, power can be taken from the steering motor to operate other mechanisms like camera shutter releases.

click on photo to enlarge

The Mill

The Mill is really a Klutz Crazy Contraptions Invention but it can be made from the parts in the Mindstorms kit.

click on photo to enlarge

animated .gif of the mill in action


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