Re: First post: best place for this?
- From: Randy Day <randy.day@xxxxxxxx>
- Date: Fri, 13 Apr 2007 23:43:16 GMT
Ed wrote:
(Earilier posted in .design - moved here by recommendation.)
Many moons ago, I was an electronics repairman in the military. Most
tubes had been replaced by then with solid state, which of course was
gaining wide use in the commercial world! I was a dabbler in
circuitry, and devoured the TTL Cookbook I bought at Radio shack
along
with any component I wanted.
Welcome.
25 years later, Radio Shack is something different and so is
electronics. I'm sure E=IR still works, but I'm not sure what they
do
with it any more!
Heh. It's a galaxy of choice out there, that's for sure.
Fortunately, most of it's dirt cheap; perfect for
experimenting.
The most I get to do with "electronics" is change
a
ballast in a flourescent light! Everything seems to be programmed -
well, I dabble in VB6 and VBA macros, but that's it. But I've got a
couple of things I'd like to see if I can cobble together, and I'm
wondering if this is a good place for me to start.
So you know a bit of programming. That helps.
Two projects right now:
Project 1: A digital metronome of sorts. A footswitch that would
count the time intervals between successive taps of my toe, average
the times, and flash a light at that interval. That would connect to
a unit by my hand that would have buttons to increase and decrease
the
time interval counts. I also want a number pad for direct entry of a
number that would set a "beat time".
I'm figuring I would need a stable frequency generator of some kind
into a pulse counter. A tap on the foot button would zero the
counter
and open a gate for about 10 seconds - within that time, every
successive tap would capture the number of pulses between taps and
increment a tap counter, add the count to the previous one and divide
by the number of taps to get the average. The average is fed into a
counter that flashes a light after this many pulses.
So far, not bad. I did things of that sort with 555s and TTL up/down
counters. But adding and averaging weren't included. And now I want
buttons that will increment that count by a plus or minus, and I want
to directly enter a count. Which means I also need a display, and I
need a circuit to convert whatever the actual pulse count is into
something meaningful in my world, and convert my entered number into
a
pulse count the unit can deal with.
Project 1 is tailor-made for a microcontroller;
not only does it have a clock source on-chip,
it'll count pulses, read buttons, flash leds,
add/average and other math. It'll also drive or
interface with any type of display you want.
You'll want to get an idea how many inputs and
outputs you'll need, pick a micro that has
enough i/o ($2 to $20), then buy or build a
programmer for it.
The PIC, the Basic Stamp and the PicAxe are
the three that get talked about most on s.e.b.
Each family has small, cheap i/o devices, with
a few K of memory; midrange devices with stuff
like analog-digital conversion, USB and RS232
i/o capability; high-end units with lots of
i/o, onboard memory space and peripherals.
Most uC's have flash memory versions, so you
can burn (program) them thousands of times
over and over; great for debugging.
The 'net has lots of freeware compilers and
schematics for uC burners, but you may need to
spend time getting it all to work together.
The commercial kits ($80 to $300) include
software and the hardware necessary to program
the chip. I bought a PicKit 2 for PIC's that
programs via the USB port on my PC. I can
compile and burn to chip with a few mouseclicks.
Got a bug? Recompile, burn again.
The downside? Learning curve. uC's like the
Basic Stamp use a variation of the Basic language
to program the micro, so there's a bit of
familiarity for you. A purchased learners kit
will have tutorials, and example code to flash
led's, read buttons, that sort of thing.
Am I out of my league yet?
You tell us! ;)
Project 2: A comparative thermostatic controller for an attic fan.
I
live in the Arizona desert and want a fan in my attic to cool things
down up there. If I set it for say 120 degrees, the thing will run
day and night for months! So I'd lke to compare the attic temp to
the
ambient temp, trigger it on when the attic raises maybe 20 degrees
above and shut off when the temps are even.
I have looked up temperature chips on the internet, but I've never
worked with any. I imagine there would be voltage comparators and
flip-flops (do they still use those?) to control the on/off.
The only temp sensor I'm familiar with is the
LM35, and only because I have one in my parts
bin. Two of those in a window comparator
circuit might work.
So how are we doing? Should I be here for help with these? Or over
in the "wishful thinking" group?
This is definitely the place. No question is too
simple, though some of the answers can be ;)
Randy
.
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