My short term goal is to be able to make terribly simple stuff, such as LED flashlights and solar-
powered fans, but it would be great if I could go from there onto building simple peripherals that
could interface with personal computers.
Just so you don't get any false hopes, note that since the
demise of DOS it has gotten *much* harder to build simple
peripherals. Used to be you could use the parallel printer
port for lots of neat interface tricks, from digital I/O to
simple A/D and D/A. But printer ports are all replaced by
USB these days, so a "simple" peripheral usually requires a
not-so-simple USB interface and driver software.
One thing that almost every computer has, however, is a
sound card. This is not only something you can use to
generate and analyze audio-range signals (see sig), but it
can also be a way to interface certain devices to the
computer. You have to deal with the fact that sound cards
don't respond to DC, nor to really high frequencies, but
that still leaves a lot of room for useful projects.
As one simple example, you can use the sound card to measure
frequency, so if you have some sensor (temperature,
pressure, etc) that only responds to DC, you can build a
simple voltage-to-frequency converter and use the sound card
to measure the resulting frequency.
No, I'm a bit empty-handed on this one. What gear do you suggest? I guess at least a multimeter is
in order.
You absolutely need a DMM, but you can start out with a real
cheapie. Harbor Freight has nifty little units that are
often on sale for a couple of bucks... including battery!
The drawback over a pro-level meter is that they don't have
low AC Volts ranges (but they do have low DC Volts). So,
use this as an excuse to build a little precision recifier
and filter circuit, so you can read AC on the DC range.
You can use the sound card to measure low AC volts,
including true RMS (which cheap DMMs don't do), but you'll
have to calibrate the inputs if you want absolute results...
there is no way to get calibration data from the sound card
driver, etc. But you can do a lot of useful things with
only relative measurements, which don't require any
calibration. (For example, distortion is a relative
measurement.)
But back to simple circuits: I always enjoyed
sound-generating circuits. They can be as simple or complex
as your abilities, and it's great fun to hear the results.
The sound card can help you visualize the results, since it
was designed for just this audio range.
It wouldn't hurt to have a "real" hardware scope as well,
but you can save that expense for later, when you really
need high-frequency or DC capabilities.
I use a 100 MHz hardware scope for general-purpose stuff,
and the sound card (and software) for audio stuff. The
"real" scope is an old analog model, so it doesn't have the
fancy spectrum analysis features that you can get on
high-end digital scopes. But (for me, anyway) I can do all
that with the sound card, plus lots more (like color
spectrograms) that the digital scopes don't do.
Best regards,
Bob Masta
DAQARTA v5.10
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, FREE Signal Generator
Pitch Track, Pitch-to-MIDI
DaqMusic - FREE MUSIC, Forever!
(Some assembly required)
Science (and fun!) with your sound card!
