Larry's Blog

THIS IS A LETTER I SENT
to George Gallant, Jim Morris
and Jim Fiske
hi
just realized something troubling
I was reading some hints for using the PIC
microcontrollers and found this:
“unconnected port bits should never
be set up as inputs”
“when floating, CMOS inputs can flip rapidly
between states and cause excessive current draw,
heating and even damaging the PIC”
So – set all unused bits of ports to outputs.
I went back to one of my books talking about
CMOS IC’s and noticed this warning:
ALL unused inputs MUST be connected to Vdd(+) or Vss(gnd)
otherwise erratic chip behavior and
excessive current consumption will occur.
other rules for CMOS were NEVER connect
an input signal to a cmos circuit when
the power is off.
another curious warning was to
avoid slowly rising and falling input signals
since they cause excessive power
consumption. it recommended
rise times faster than 15 usecs
I think I have been lucky so far
but I’m certainly going to observe
these precautions.
Regards.
Larry Keegan in Stoneham, MA

I have re-designed and simplified my circuit for my PIC programmer.
This circuit is connected to my laptop and a 5 volt power supply.
It takes about 25 seconds to go from assembly language program
to the burned in PIC microcontroller ready to run.

IN BRIEF:
1. Gave a talk to the QRA radio club on PIC Microcontrollers
2. Wired up a MING xmtr & rcvr & got it working
but want to package it more nicely and affix some PICs to it
3. Stripped apart som RC cars & trucks and set up an
RC system with a small relay attached to rcvr
4. Writing a PGM to read the infrared sigs from a handheld REMOTE.
Interesting article in SERVO mag outlines methodollogies.
PWM seems to be the most popular I think zero pulses are about 400 usecs
wide & ONE pulses are about 1200 usecs wide. There are about 34 pulses
& about 12 of them unique and determine the individual code
5. I’m in the process of firing up some of my other old laptops
The hell with batteries – they are expensive . I plan to solder conect
wires to the contact points where batteries would connect. They operate on
a whole range of voltages.

HERE ARE THE BREAKTHROUGHS
(1) MY SPEAKING COUNTER WILL NOW COUNT CONTINUOUSLY TO 999
(2) MY PIC PROGRAMMER SOFTWARE NOW OPERATES A HUNDRED
TIMES FASTER!!
(3) MY DOS BATCH FILE NOW RUNS WITHOUT ANY INTERVENTION FROM
ASSEMBING THE PROGRAM THROUGH PRE-ERASING THE PIC, WRITING THE CONFIGURATION WORD, CREATING THE INTERMEDIATE FILE, TO LOADING THE PROGRAM ONTO THE PIC. IT ALL HAPPENS IN 15 TO 20 SECONDS.

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Take a look! For a while I couldn’t find my way around my shop!
My white counter-top was covered with resistors, batteries, capacitors, IC’s , wire, connectors, breadboards, PC boards, relays potentiometers,screwdrivers, pliers, wire strippers, scissors, electric tape, stands of solder, machine screws and nuts, pieces of metal of all shapes, relays and switches. Well, look what has happened!

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Well here it is!
THE SENSBOT – a robot the senses obstacles
and navigates to avoid them.

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It works! The robot LIGHT-SEEKER was completed
and here ii is.

Here is how it works. It rotates around little by little
and checks for a light source ahead of it.
When it finds a light source it beeps and proceeds
in that direction. After a short distance it checks
if the light source is still there. If so it continues ahead,
otherwise it rotates again and seeks a light source.

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This new robot is pictured on the right. It is called
STEPBOT and is powered by stepper motors.

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I made 2 new QBASIC pgms for programming the PIC. These programs do not solve a problem I have been working on., but they clean up and speed up the process.

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Here are some new happenings in my PIC programming adventures.
This robot moves forward for several seconds then makes a 90 degree turn.
It continues to do this moving in a square path.

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