FINAL WRITEUP INFO
mtg 4: EAGLE PCB CAD
lab 3 html
papers Johnny 5 pdf
mtg 3: laser cutter & HPGL
lab 2 html
HPGL manual pdf
mtg 2: intl ground vehicle comp
mtg 1: LogoChip & Bus Devices
metacricket paper html
UML305DEV board assembly
lang ref pdf
PIC 16F876 pdf
lab 1 html
91.548 Lab 1: LogoChip
due February 3
In this lab, we will experiment with current flow (i.e.,
destructively test LEDs) and learn how to create digitally-controlled
devices using the LogoChip.
- Using experimentation, determine how much energy is required to destroy
a cheap T1-3/4 (standard/large) red LED. Does a brief burst of high
current or a longer period of lower current make a difference?
- You have a budget of about 10 LEDs. We have lots, and they cost
about 5¢ each, but pretend the supply is not unlimited.
- Ohm's Lab is V = IR (voltage = current * resistance). You can
measure current by running it through a resistor of known resistance
and then measuring the voltage drop across the resistor (I = V / R).
Or, you can run the current through a digital VOM (assuming it's less
than 10A) and get a reading. Or, you can use the instantaneous
current display on the lab power supplies.
- An LED is a non-linear device. This means it does not obey Ohm's
Law. In normal operation, it is modeled as a diode, which means it
has a fixed voltage drop.
- Describe your results in Joules, using the 1 J = 1
Watt-second definition. Talk about current flow, voltage drop, and
Using the Getting Started
with the LogoChip document, wire up the LogoChip on a breadboard,
get its boot flash, then hook it up to the PC, and get
bootflash to run from the software's command center.
Hook up a beeper, configure its pin to be an output, and write
a loop that makes it beep.
- Complete one of the following five activities/experiments.
Alternately, using these, the Predko book, or anything else as
inspiration, design your own cool project using the LogoChip. (If you
choose to do something other than one of the ideas here, please check
it with me first.)
- Design a stepper motor control circuit using the LogoChip. We
have 4-phase unipolar stepper motors in the lab. You may be able to
run them directly from LogoChip digital outputs, but you'll probably
need driver transistors. Write a program to make the stepper motor
go. Implement position control (i.e., commanding the motor to rotate
to a specific position) and velocity control (i.e., cause it to run
freely at a specified number of clicks per second). The velocity
control program should keep track of the absolute position as well.
For reference, see the Predko book, pp. 289292. Also, we
have motor driver chips, the TI SN754410NE.
- Implement a programmable display using a 5x7 LED array
component. Create a multiplexed row/column scan method so that only 7
LEDs are on at one time. Create a character font so that an arbitrary
symbol from the ASCII character set can be displayed.
- Implement a driver for the DevanTech sonars that are part of
the Botball kit. Have the LogoChip indicate distance to target in a
standard unit of length.
- Create the following experiment in the spirit of Harold "Doc"
Edgerton's seminal strobe light work. Connect a piezo to the
LogoChip, but instead of using it to produce sound, use it as a
microphone. (When it receives a loud noise, it should produce a
signal in the 50 mV range, which is detectable by a LogoChip analog
input.) Use this to implement a clap detector.
Then, after hearing a clap, light a bank of LEDs for a short
interval (10 to 50 milliseconds or so). Now you have a system that
when it hears a clap, it produces a short burst of light a moment
later. (Transistor drivers may be needed to get adequate light from
the LEDs, because they should only be turned on for a very brief
Finally, take the setup to a darkened area along with a regular
latex balloon and a pin. Pop the balloon near the piezo
microphone and in range of the LED illumination. You
should see the open shell of the balloon being popped, before it has
collapsed into shreds!
(This experiment was suggested by Robbie Berg.)
- Build a simple digital-to-analog circuit (DAC), perhaps using four
bits and a resistive network to create a stepped range of output
voltages. Load up some sampled or computed audio data (e.g., a sine
wave) into the LogoChip, and write a program to spit it out at a rate
fast enough to make sound. Listen to the output and look at it on the
scope, and describe your results.
For #1 and #3, prepare up a Lab Report to be turned in.
This should be a written description and/or circuit diagram and/or
code listing (as appropriate) explaining what you did and how you came
to believe your interpretation of what was going on was correct.
Thursday, 27-Jan-2005 16:09:01 EST