>>>READER-TO-READER QUESTIONS AND ANSWERS
many examples. After the manufacturer's published literature, some people
consider this book to be the definitive
And finally, if you get stuck, there
are a variety of online resources for
you to ask specific questions.
Microchip has their own online
forums and you should also check out
the MIT PICList email list at
#3 Start with a simple microcomputer like the PIC with only 33 instructions to learn.
You might start out with a
microcomputer simulator. It is a piece
of software that runs on your PC and
looks like a micro. There is a window
where you write code; “move A,B”
and other windows where you see the
number move from B to A or A to B,
as you will soon know. Microchip
MPLAB is free; a number of
companies give away their development software.
If you want to go straight to hardware, search for the BASIC Stamp (as
there are many competitors). You
write in Basic (some allow assembly),
but you have a tiny computer up and
working in minutes. There are
hundreds of examples of working
code and good help forums.
Go to any microcomputer
website. MicroChip, TI, Zilog, Silicon
Labs, Atmel, etc., and look for
development boards. You need a
board with a microcomputer, LEDs,
buttons, and places to add more parts.
I have SiLabs C8051F005 development kit that comes with a good
simulator/compiler. SiLabs and TI have
boards as small as your thumb.
Mikroe.com has beautiful large
boards. Good luck!
#4 Programming is a large topic, so
the answer will be a bit general. Here
is a quick run-down of the basics and
places to look.
The most important thing to know
is that learning a language is only
a small part of programming.
Understanding algorithms, data structures (how to store and access data),
and overall design are extremely
important when writing programs with
more than a few hundred lines of
code. I'd recommend getting a book
on data structures and another on
software engineering (that's the fancy
term for planning and managing
As for the actual languages to
learn, programming for computers is
rarely done in assembler these days,
unless you are working on device
drivers or performance-critical applications. In general, high-level languages
such as C, C++, C#, Java, and Visual
Basic are much more prevalent. There
are numerous books dedicated to
each of these languages and they
cover them in lots of detail. There is
still a lot of value in learning assembler, however, as it gives you a better
understanding of how the computer
really works. One of the best books on
computer assembly programming is
"The Art of Assembly Language
Programming" by Randall Hyde. It covers the Intel x86 assembly language
and covers many of the underlying
concepts needed for successfully
writing programs in assembler.
If you are more interested in
programming microcontrollers, there
are fewer languages to learn. Many
microcontrollers can be programmed
using high-level languages such as C
or BASIC. This makes programming
these devices much easier and also
makes the source code much easier to
understand after the program has
supply only enough current to maintain the voltage at 6. 8
volts. Using an LED as the voltage reference provides some
temperature compensation. To adjust the pot, connect a
fully charged battery and adjust for 6. 8 volts at the battery.
If the battery is not fully charged, set the pot at its lowest
(toward R4) and check periodically until the voltage rises
above 6. 8, then back off to 6. 8 volts.
The TIP41 will get hot charging a dead battery, so a
heatsink is advised. Mouser part number 532-6237B will
probably work. TIP41A, B, and C are also okay to use.
Mouser has no minimum order ( www.mouser.com).
#3 A simple solution would be to use a handful of rec-tifing diodes, capable of handling the current of the battery
charger. Connect the diodes in series to get a 5. 5 to 6 volt
drop and connect them in series with the six volt battery.
#4 A battery maintance or float charger just replaces the
charge lost due to internal leakage. A resistor can be placed
in series with the output of a 12V maintenance charger for
use on a 6V battery. If the battery is rated at 24 amp-hours
and is dead in 30 days (720 hours), it must be losing charge
at a 33 milliamp rate. To drop 6V at 33 mA, use a 180 ohm,
1/2 watt resistor. The resistor value may have to be adjusted to match the actual discharge rate of your battery. If the
discharge rate is much higher than 33 mA, look for a sneak
discharge path in the tractor electrical system. Another
approach is to use an LM117 regulator to drop the main-tenace charger output. Set its output to about seven volts.
West Islip, NY
#5 Here are two sites where six volt chargers are
available: www.atbatt.com/product/6840.asp and www.
If you want to
Figure 2 build your own float
charger, refer to
Figure 2. A 12 volt
DC wall wart such
as stock #16770
com can be used
with the circuit.
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