Synopsis: Over the past weekend, I spent the time to take the sensor analog and digital interrupt logic off the breadboard and onto a more semi-permanent perf board. In the process, instead of a single sensor circuit which I’ve been using on the breadboard, this perf board incorporates all the circuitry for 4 sensors ( hand and foot X 2 lanes.) This perf board implements the schematics in Part 5 of this series with one exception...I added 4 LED indicators through another driver to show on-board when a sensor “fired” due to a touch.

Also, in this article are a couple of movies that show a single-sensor alpha test on a climbing wall.

2 Lane, 4-sensor Perf-Board

Here’s a picture of the perf-board that contains the sensor detection and microcontroller interrupt logic for a two-lane speed climbing system. The microcontroller is on a separate board. The schematics for this board can be found in Part 5 of this series. The 4 orange potentiometers on the upper left of the board are there to adjust the sensor sensitivity.



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Tags: Schematics, IR Sensors

I took a short break from the prototyping workbench to catch up the project documentation. This one in the form of schematics. Using Eagle, I created a short set of schematics focused on various subsystems of the speed climbing timing system.

They are:

1. IR Sensor and Interrupt Logic
2. Power Regulation
3. Microcontroller Interfacing
4. RJ45 pinouts for the Modular Connections

I won’t spend much time explaining the schematics. They could well change as I get further into this.

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Tags: Schematics, IR Sensors

Synopsis: This is a video to show the initial integration of the IR sensors with the stop switch interrupt of the microcontroller. There’s more work to do as you will see. Later in the article are a couple videos which show the system working after an EMI issue caused spurious interrupts.

The basic integration of the IR sensors with the AVR is:

• IR Sensors have a high frequency component and the overall wave goes from about .8v to 2.5-3V.
• I take the IR signal into a low-pass filter to clean up the signal and remove the high frequency components
• That signal goes through a non-inverting comparator and amps the signal to the rail when the IR beam is reflected with a hand
• The output of the comparator goes to a hex inverter (74LS14) schmitt trigger
• The output of the schmitt trigger goes to the interrupt of the ATMega128.

Video below the break....
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Tags: ATMega128, Max7219, LED display , Speed Climbing, SPI Cable, Watch Crystal, XBee

In Speed Climbing Timing Part 1, I introduced the touchless sensor concepts of a speed climbing timing system. In this part, I’ll demonstrate the basic controller and the timing functions as well as the display driver.

The display is based on a Maxim 7219 LED multiplexor. The controller is an Atmel AVR ATMega128. I’ve developed the Max7219 driver code and the basic timer to deal with a two-lane speed climber competition.
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Tags: ATMega128, Max7219, LED display , Speed Climbing, SPI Cable, Watch Crystal, XBee