School, hobby electronics
This material is not 'polished'!!
As I surf the net, I come across various things that I wish someone had told me about. In theory, one day it will all be available in the polished sections of my website. In the meantime, if you're willing to 'dig' through some disorganised material, you may be rewarded with gems'!
School, hobby electronics.
This material is mostly about doing things with digital electronics, including PICs and 6802
microprocessors. Not much about how to add soundcards, hard drives, etc, to a pc.
However, there is material on circuits you might want to
build and connect to a pc via a parallel port, ISA bus, etc.
In some cases, the text is snipped from other sources. Therefore, among other things, the
personal pronoun may not refer to the editor of this page. If, on the
other hand something is identified as coming from 'TKB', he IS the pages's editor!
Material from earlier versions of this page has been 'polished' into more organised pages. Click here to visit them.
Oops... the page WAS in two sections... general stuff at the top, then notes about specific problems, projects, products on offer (e.g. digital i/o card) in second section. I messed it up a bit, but will try to re-sort it in ue course.
Click here for 'unpolished' material about using an MS-DOS / Windows computer's parallel port to control things or sense the 'outside world', or click here for 'polished' material.
Ad from page's editor: Yes.. I do enjoy compiling these things for you...
hope they are helpful. However.. this doesn't pay my bills!!! If you
find this stuff useful, (and you run an MS-DOS or Windows pc) please visit my freeware and shareware page,
download something, and circulate it for me? Links on your page to
this page would also be appreciated!
Click here to visit editor's freeware, shareware page.
General Stuff
===
Q: I have an idea for a pc card, but I'm more of a software
kind of guy. How difficult is it do build your own ISA or PCI card? My
device really isnt too complicated, more or less an interface for several
buttons, lights, or whatever (input and output, digital and analog), that
could be read from software (think of an advanced form of a gamecard). I
realize I may be able to do some fancy stuff, so I could use the parallel or
serial ports, but that may not provide the horsepower I'd need.
A: An ISA card is dead easy, PCI is comparatively horribly complex.
Find a copy of "Interfacing to the IBM-PC" for good info.
I'd recommend cypresses $99 USB devkit, but they are backlogged, ordered
5 weeks ago, they say 2 weeks till they ship.
===
Good UK dealers in second-hand, clearance, etc.:
Bull: [please send me url if you look it up]
Greenweld: www.greenweld.co.uk,
Display Electronics: www.distel.co.uk
===
Outstanding UK source for components... superb service,
good CD catelogue (£5): Electromail
===
Source code for three simple PC terminal programs (two in ASM and
one in C) is available on the TCJ Web site
http://www.psyber.com/~tcj/
From an article in the
current (date uncertain)
issue of The Computer Journal, look on the 'Current Issue'
page. Also from the same issue is an article about using the 16550
with a 6502. Also available for download is Z80 and 8031 serial
port
code from previous issues.
- -=-=-=-=-=-=-=-=-=-=- The Computer Journal -=-=-=-=-=-=-=-=-=-=-=-
Dave Baldwin, Editor/Publisher | (800) 424-8825 or (916) 722-4970
Email: tcj@psyber.com | Small scale computing since 1983
Hands-on hardware and software | Support for older systems
BBS: (916) 722-5799 | FAX: (916) 722-7480
-=-=-=-=-=-=- Home page "http://www.psyber.com/~tcj/"-=-=-=-=-
===
Basic information about Pics... stuff to learn about them,
and start writing simple programs:
http://www.dontronics.com/picnpoke.html
for a demo tutorial.
SimmStick(tm) Atmel & PIC proto PCB's. 30 pin Simm Module Format.
For more details, send a blank message to mailto:info@dontronics.com
or mailto:simstick@dontronics.com or mailto:basics@dontronics.com
===
[tb note: Next WAS a great place for people who build their own
computers from raw chips. Seems to have been taken over by people assembling pc clones
from m/b, dirve, etc components]
WELCOME TO ALT.COMP.HARDWARE.HOMEBUILT (v.16 Modified 5/3/96)
This file contains frequently asked questions (FAQ) and general
information pertaining to the newsgroup alt.comp.hardware.homebuilt.
It is maintained by Mark Sokos (msokos1@gl.umbc.edu). It is posted
every two weeks to the newsgroup alt.comp.hardware.homebuilt. The
latest version may also be obtained by sending an e-mail request
to the above address.
This file is also available via FTP from rtfm.mit.edu in the
/pub/usenet/alt.comp.hardware.homebuilt directory
A DOS text version is available from Dave Baldwin's FTP site:
ftp.netcom.com /pub/di/dibald/
An html version, maintained by Hai Pham, is available online at:
http://www.qucis.queensu.ca/home/pham/homebuilt/achh.faq.html
This file is copyright 1996 by Mark Sokos. It may be freely copied and
distributed as long as this notice remains intact and the file is not
modified, and no fee is charged for its duplication.
===
The Computer Journal... stuff for homebrewers... NOT 'How do I
install new hard drive in pc' type Q's. There is an archive of faqs.
http://www.psyber.com/~tcj/faqnfile.html
Specific problems, projects, products
===
Q: Can anyone point me to information about interfacing a 3.5" floppy (as
found in pcs) to a small single board computer of my own design? The
software for management of the sectors doesn't particularly worry
me... the big 'stumbling block' at the moment is the hardware side.
I'm hoping to find what it will take to let me connect an
over-the-counter disc drive to something my sbc can 'talk' to on a 'I
want to read or write this sector (with this data)' level.
Most floppy controller chips do not make it that simple. You will
need some software to initialize the transfer (track , head, sector),
perform the transfer and then cleanup afterwards if there are errors.
While not difficult it's clearly not a "give me sector".
Does it have to be DOS format? How about Wozniak's floppy I/F for the
Apple][? I think it was all done with a few TTL chips, originally.
The apple interface while appearing to be simple really pushes all the
work on to the CPU. It also used a very modified drive as memory
serves.
He would be far better off using current style controller chips as
they do a fair amount of the work and are simple to use with existing
formats and drives.
===
[tkb didn't test...]Information on IDE and parallel port interfacing:
ftp://iglou.com/members/ITU/pc-int.
See the ATAr4c.txt and ide-tech.txt files for more info.
===
[tkb didn't test...]
Talking to a floppy control from NC4000:
ftp://ftp.hal.com/pub/elvey/floppy.txt
Using a non-DOS machine to talk to a DOS disk
ftp://ftp.hal.com/pub/elvey/disk.txt
...... and another answer....
You can visit national semiconductor web site at
http://www.national.com/catalog/Mass_Floppy.html
to download
datasheets for floppy disk controllers. You may also obtain more
information from Intel. Try to get a hold of the embedded controller
handbooks from Intel. They have a lot of information on writing
software to operate these controllers in roll your own computers.
===
Q: I'm trying to design an expansion board for the ISA bus in my
computer, and I need some references for timing and use of ISA
buses, also programming tips to access a device on the ISA bus
would be appreciated.
A: There's an article about the ISA bus on my web page. You can also
find a schematic (in ASCII text, for those with "graphically challenged"
software) in Steve Walz's ftp site for a parallel port. There's also
an 8255 based I/O card listed under the projects section of the FAQ
(also on my web page).
Programming is as simple as IN and OUT instructions, or if you are
using C, inport() and outport(). This will transfer data to and from
an I/O device on the bus. You *can* make your device memory mapped,
but it's usually not a good idea.
- Mark Sokos (msokos1@gl.umbc.edu) Electrical engineer, computer geek (er,
programmer), no-talent bum musician, and perpetual student
http://www.gl.umbc.edu/~msokos1: alt.comp.hardware.homebuilt FAQ, ISA and
other bus info, and schematics (mostly audio).
===
Simple PIC prgmmer at...
http://www.isc-durant.com/nolan
===
Someone looking for a 4 channel, 12 bit ADC equipped chip got the reply...
What about using a PIC14000 ? It's a PIC 16Cxx core, but it has a
slope-type ADC with 16 bit resolution. It's not fast (according to the
data sheet, it takes 16ms to do a 16 bit conversion), but it should be
suitable for DVM type things.
You can get the data sheet in .pdf format from the microchip web page.
Take a look at :
http://www.microchip2.com/products/micros/mid/index.htm
and follow the obvious link.
The gates in my computer are AND,OR and NOT, not Bill
===
a PIO-12 which made it pretty simple to read and/or
write 24 single bits on this card
at http://www.keithley.com/Metrabyte/
Another good page for i/o cards, etc:
http://www.rwbeck.com/services/i&c/pc-based.htm
===
We are pleased to announce the availability of two new IC's in our
product lineup:
The EDE700 Serial LCD Interface IC - provides a serial interface to any
text-based LCD display; a 'backpack on a chip'. Allows the use of
popular surplus LCD displays with Stamps & Microcontrollers using only
one data line. Has unique 'row shift-up' feature, and allows data to be
read back from the display in memory-critical applicatons.
The EDE1400 Serial to Parallel Printer IC - provides a serial interface
to most Parallel-Port printers. Allows Stamps/Microcontrollers to print
data/text on a standard parallel printer using only one data line.
Great for data logging, etc.
Datasheets and pricing information for both IC's are available on our
website at http://www.netins.net/showcase/elab in the 'Integrated
Circuits' section.
Thanks,
Todd Peterson
E-Lab Digital Engineering, Inc. (712) 944-5344
P.S. - We do continue to carry and support the EDE1200 Stepper
Controller IC and the EDE300 PC Interface IC.
===
On [[Oh heck! I (tkb) lost the URL!...]] you can download a free
program that creates an oscilloscope from a PC with a sound card...
and other PD stuff!
This was a usegroup post... If I remember, I'll look in deja news..
if you get there before me, the URL would be of interest.
===
Some days ago, there was a posting on this topic and I thought that I
would shed some light on this topic:
Controlling relays with a parallel port would be easier because the
parallel port data lines are TTL logic-level signals. But there a
several reasons why you might want to use a serial port. First, fewer
wires are required (just two, instead of nine or more). Second, serial
wires can be a lot longer, (upto a half a KM at low baud rates)
(compared with just a few meters for parallel) without degrading the
signal. And third, serial ports are more standardized; whether or not
the computer is PC Compatible. This is essential if your computer
happens to be a MAC or a Sun workstation.
Decoding the RS-232 Signals is a job for a microcontroller (single chip
computer). Fortunately, you dont have to program the microcontroller
yourself; you can a PIC16C54A programmed exactly for this.
If you need more details on this fantastic chip that can turn on and off
relays, solenoids, motors or lamps, email me, I'll be happy to send you
a circuit diagram. : technova@pacific.net.sg
===
I came across the following, which purported to be help on finding electronic design information on the internet.
Archive-name: sci/electronics-search-faq
Electronics Search FAQ - POINTER
http://www.eetoolbox.com/srcnet.htm
http://www.cera2.com/srcnet.htm
http://www.eg3.com/srcnet.htm
------------------------------------------------------------
This FAQ focuses on sources of information useful for electronics
and electronics design. It lists resources of various types. Please email suggestions to comments@eg3.com.
Thanks!
------------------------------------------------------------
CONTENTS:
ALL include active WWW links to the relevant resource
* GENERAL SEARCH OVERVIEWS
* THE BIG THREE
-- FAQ's and Technical Reports: Finding Them
-- USENET: Searching for Groups and Searching USENET
-- World Wide Web: Major Search Engines
* OTHER REALLY IMPORTANT EE RESOURCES
-- Conferences: Locating Conferences on EE Subjects
-- FTP Sites: Finding Source Code and Software
-- Mailing Lists
-- Publications: Major EE Publications & Web Resources
-- Smart Semiconductor Search: NEW Search Engine, Searching
ALL major (embedded) chip vendors
* MERITORIOUS EE SEARCH RESOURCES
-- (..snip... various!)
-- Embedded Systems Index
-- Industrial Embedded Computing
-- Microcontroller/processors
-- VTS Buyers' Guides by Topic Area
* INTERNET RESOURCE PAGES
-- (... again.. snipped, various, e.g....)
-- Artificial Intelligence
-- Ada, Assembly, C & C++, Compilers, Emulators, Forth
-- FTP Sites, Mailing Lists, Robotics
===
Free tutorials on
- breadboarding your own PC Interface Card,
- breadboarding your own Parallel Port Interface Box
- Infrared emitter/detector (good for encoder wheels)
Available downloads:
- PCB artwork
- QBasic/Turbo C source code
View/download pdf files on:
- DC motor interfacing (speed and direction control)
- D-to-A converter interfacing, and interfacing
- Relays (turn on home applicances with your computer)
Additional files on:
- A-to-D converters (e.g. temperature sensor readings)
- Stepper motor interfacing
- 16-key keypad interfacing
- LCD interfacing
Users network:
- See hyperlinked list of users and their PC Interfacing
interests
Visit and enjoy the free downloads:
http://www.boondog.com
===
Someone asked for EPROM programmer schematics. He was pointed to...
Consult my site's FTP Gateway in my LPT/ and EPROM/ subdir's. I have some
info on the basics of this stuff, and reading the databooks of prospective
parts you wish to program is very instructive.
The Vcc-supervoltage for CMOS
devices is important to get right for specific parts.
Steve Walz rstevew@armory.com ftp://ftp.armory.com:/pub/user/rstevew
-Electronics Site!! 1000 Files/50 Dirs!! http://www.armory.com/~rstevew
Europe:(Italy) http://ftp.cised.unina.it/pub/electronics/ftp.armory.com
tens of files in LPT directory alone
===
While Lattice's system is _very_ good, it isn't really necessary - you can
build fairly simple designs using standard 74xx logic. I've found that
Lattice designs are more prone to errors than simple logic ones - mainly
because the Lattice system makes building complex circuits so easy that you
make silly mistakes when entering them.
For example ISA cards, there are lots of sources - I'd suggest your first
port of call should be the a.c.h.h FAQ at
ftp://rtfm.mit.edu/pub/usenet/alt.comp.hardware.homebuilt/
After that, a good book I'd recommend is the Art Of Electronics by
Paul Horowitz and Winfield Hill, published by Cambridge University Press (I
can't find my copy now, but I'm sure someone else can quote the ISBN). It's
got a whole chapter on ISA interfacing which should explain most of what you
need.
Hope this helps,
Theo Markettos, Liphook, Hampshire, UK
===
Q: I need a circuit which takes a constant 5 volt feed as its
input and produces a 5 volt ouput ONLY if the current air temperature is 2
degrees C or below.
The circuit must be as small as possible (I have
about 2 sq cm on the board to work with) and it must be cheap!
A: There'd a very simple thermostat circuit on our www site - 4 transistors and
4 resistors.
Certainly very cheap, and if you use miniature resistors, it should fit your
space.
Anyway - it's a fun circuit.
/ | Richard Torrens
/ | postmaster@4qd.co.uk http://www.4QD.co.uk
/ | |
/ /| | We manufacture
/ / | | MOSFET controllers for battery operated motors
/_/__| |____
/_____ ____\ Site also contains FAQ sheet on motors & controllers
/ _ \| | _ \ and a selection of interesting circuit diagrams
===
Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
The above site, to quote from it,.... "features Samuel M. Goldwasser's latest and greatest "Notes on the Troubleshooting and Repair of..." series of comprehensive repair guides for consumer electronics equipment and other household devices. There is also a great deal of other information of interest to the electronics hobbyist, experimenter, technician, and engineer. In addition, there are a variety of documents from other sources and many links to other useful and often fascinating web sites."
===
There are many ways of doing this but given that you want to use relays, a
simple driver circuit will boost the current output of your PC, see below:
--- sam :
Latest Sam stuff: http://www.repairfaq.org/sam/
Lasers: http://www.repairfaq.org/sam/lasersam.htm
http://www.misty.com/~don/lasersam.html
Driving Relays with DC Coils:
Small relays are designed to be connected directly to a TTL output. These
will have 5 VDC coils rated at a current as low as 10 mA or less. Larger
relays with 5 VDC coils may require as much as 100 mA or more so a beefier
driver (beyond a TTL logic gate) may be needed for some of these. Relays with
higher voltage DC coils can also be used. For a given type, coil current is
inversely proportional to coil voltage. Therefore, using a relay with a
higher voltage coil may be easier if a suitable power source is available.
As always, when driving an DC inductive load, a back biased 'free wheeling'
diode is placed across the coil to provide a path for the coil current to
continue flowing (and ramp down to zero relatively slowly) when the driver
switches off. This prevents any inductive voltage spike which would result
in stress on the driver and/or logic circuits and may generate excessive
electrical noise.
The following are several alternatives for driving these relays (12 VDC, 10 mA
coil assumed; typical contact configuration shown):
o--o NC o--o NC o--o NC
C o--o/ C o--o/ C o--o/
o--o NO o--o NO o--o NO
V+ o---+---+ V+ o---+---+ V+ o---+---+
_|_ )|| _|_ )|| _|_ )||
1N4002 /_\ )|| 1N4002 /_\ )|| 1N4002 /_\ )||
| )|| | )|| | )||
1/6 7406 +---+ +---+ +---+
|\ | | D |
ON-H o---| >o---+ R1 |/ C .|---+
|/ ON-H o---/\/\---| 2N2222 G||<--. 2N7000
1K |\ E ON-H o----'|---+
TTL Open Collector Driver _|_ S _|_
(HV output if V+ > +5 VDC) - -
Bipolar Transistor MOSFET
Depending on specific coil voltage and current, devices other than those shown
may have to be used as the drivers.
Someone asked....
I'm trying to control 115VAC60Hz sockets via software/parallel port of
my computer. I'd like to use relays (If possible), but I know that the
parallel port on an old PC/XT can only sink a few mA of current. My
relays that I have already are 12VDC, at ~95mA, peaking at 100mA. Yes,
yes, they're large, but they're the only ones that I've been able to
find that don't constantly arc at the contacts.
I was thinking some sort of circuit that uses transistors or
optoisolators, and uses parts that I can go buy at Radio Shack (I need
this soon, ~2 weeks, and mail order takes too long).
My program is written QBASIC (not fancy, gets the job done, and runs
well on the XT) and will output a signal to pins 2, 3, 4, 5, and 6. The
relay must close when the pin is high, and release when the pin is low.
If possible, I'd like to avoid damaging the computer. :-)
Does anyone have experience with this, or know of web sites with
information? I'm trying to go for a minimum parts/cost. Thank you very
much! Please, if possible, drop replies in my mailbox as I don't often
read these newsgroups. Thanks again!
--
Colin Guillas Ringmaster For Commodore Ring
http://cbmring.home.ml.org ringmaster@ottawa.com
Kinetix Web Design http://kinetix.home.ml.org
High Quality, Low Priced Web Design For Everyone!
----
The best way to do this is to use an intermediate transistor, such as a
2N3904 NPN, or 2N2222, or similar, and to control the base with any old TTL
signal through a 1Kohm resistor, and to ground the emitter, and to suck
current through the relay coil into the collector-emitter path. It's nice
to pull up the base through another 470ohm resistor to Vcc if the output is
a weak HI or open-collector. TTL always sinks current better than sources
it. This is the classic limitation to driving things like LEDs and relays.
O V=12Volts O
| +----|
> | )||
< --- )||
> /_\ )||
| | |
| +----|
| |/
>---\/\/\/---+---------|
|\v
|
_|_
-
There are numerous values of resistors for this simple switch biasing that
work on different kinds of TTL outputs, and they are best determined by
knowing the definition of saturation and cutoff for a transistor and
choosing the resistances to go from all the way off to all the way on,
without extreme saturation, though for slow switching, even this shouldn't
matter. Some care needs to be taken not to excedd the voltage or collector
current rating of the transistor. With TTL and most small relays, this is
not at all a problem.
-Steve
--
-Steve Walz rstevew@armory.com ftp://ftp.armory.com:/pub/user/rstevew
-Electronics Site!! 1000 Files/50 Dirs!! http://www.armory.com/~rstevew
Europe:(Italy) http://ftp.cised.unina.it/pub/electronics/ftp.armory.com
===
The ULN2003A is a cool family of TTL->relay drivers.
See my web page for an example schematic.
http://www.seidata.com/~jzigan/pic/pic_sub.html
I'm trying to control 115VAC60Hz sockets via software/parallel port of
my computer. I'd like to use relays (If possible), but I know that the
===
Good books about building hardware and programming with the exellent 6802 microprocessor:
Introduction to 6800/6802 Microprocessor Systems, Simpson & Terrell, ISBN 0 408 01179 3
Twenty Tow Microcomputer Projects to Build, Use and Learn, Metzger, ISBN 0 13 934712 7
===
EPE Net Work written by Alan Winstanley is our topical column specially written for electronics enthusiasts, technicians and students having Internet access. Each month we suggest useful sites whose URL's are enabled here for you to point and click. We are also building up what (we hope) is a useful resource in the form of the Net Work A-Z Index, an archive of all links ever suggested. We accept no responsibility for the content of these sites, which are provided for you
http://www.epemag.wimborne.co.uk/network.htm
(asked for TKBOYD/ele1b and ele1p boost, (under 'Electroniics...' 14 Sept 98)
===
(URLs not tested...)
Jason J. Campbell asked for information on humidity sensors. The following leads appeared..., in a long and helpful post from <>, which I've simply edited.
a) HI-Cal manufactures an analog sensor with a linear output from
0% to 100%.
b) Sensors made for clothes dryers were suggested. (Said to be made by Siemens and Philips, among others) but a follow-up (seems likely to be right) said:.
Those are usually *temperature* sensors. They sense the rise in dryer
exhaust temperature that occurs when the clothes become dry and there is
no more water left to evaporate and cool the air.
...but THAT gave rise to....
Not necessarily so. Have a look at the Philips and Siemens HUMIDITY
sensors, which have a polymeric variable capacitor inside a perforated
housing. The variable capacitance relies on the hygroscopic properties
of the polymer and the very high dielectric constant of water vapor.
All metallic materials are carefully designed to be non-reactive. These
sensors are surprisingly stable and linear.
c) Hycal makes such a product, El Monte, CA. (818) 444-4000.
http://www.hycalnet.com
The IH-3605-B measures relative humidity from 0 to 100% over a
temperature range of -40 to +185° The three-pin SIP operates from
a 5V supply and provides a 0.8 to 4.0V linear output, corresponding
to 0 to 100% relative humidity. Two-point calibration establishes
+/-2% accuracy. The sensor resists contaminating vapors and is
unaffected by water condensation.
d) Panametrics is another supplier. 221 Crescent Street, Waltham , MA, 02154 USA
fax 617-894-8582
e) Sensors Magazine has sensor information http://www.sensorsmag.com
f) Although the wet bulb / dry bulb scheme may be useful for calibration,
wouldn't it be a pain for data logging? Always keeping that wet bulb
from drying out, etc.
g) OMEGA offers their NOMAD line of low-cost dataloggers and have a true dual
channel T/H logger for only $185. You can download a 2-page datasheet at
http://www2.omega.com/Omega/products/nomad.html
h) ONSET offers the HOBO and StowAway, which are low-cost single-channel RH
loggers. See http://www.onsetcomp.com/
i) Try Global Water at url http://www.globalw.com
j) A number of companies make humidity sensors, but many sensors, like the
one from Philips, are sensitive to some airborne contaminants. Others
will not tolerate humidities above about 90%. Those from General Eastern
and HyCal, I understand, can tolerate 100% relative humidity, so can be
submmersed in water.
k) A few addresses concerning digital TEMPERATURE sensors:
http://www.dalsemi.com/prod_info/thermal/index.html
http://www.nsc.com/pf/LM/LM75.html
http://www.analog.com/products/index/20.html
Good luck with jour search. PS a good address for electronic parts:
l) Try Omega
http://www.omega.com
mailto://info@omega.com
They're very good about catalog information in book form which you ought to
have for reference.
m) You can only detect chemically active gases with chemical detectors.
CO2 needs a photo/spectral device - capital equipment investment here.
Humidity is measured easily with devices made by Philips, Dickens and
others. These work on a variation of dielectric constant with absorbed
h2O.
n) Panametrics makes a nice sensor that is relativly inexpensive. The capacitance
changes with the relative humidity. You can use it as the capacitor in a 555
circuit and easily measure humidity this way. They give a couple of circuits
for getting an analog output from humidity.
o) Philips do a humidity sensor called a 'Humicap', capacitance changes
with humidity, it can be used with a simple 555 timer circuit to measure
humidity. Check out the Analog Devices AD590k for temperature
p) Phys-Chem Scientific have a
humidity sensor which they sell in the form of an evaluation kit, 3
sensors and a lot of documentation for $100. The sensor is their
EMD-2000. I have built a board that does all the signal conditioning
at the sensor. (The sensor requires AC drive, and a log amp to linearize
the output.) I've been using it for about 3 years, continuously.
q) Keep in mind that by changing temperature the RHD relative humidity
will also change. An example you can estimate that a 10° Change of
temperature will half or double the RHD. Lower temp. = higher
humidity.
r) The sensor we have been using in one of our project is like a variable
cap. We used the cap. change for an oscillator circuit. and we
measured (or compared with an reference oscillator) the frequency.
s) If you do an allignment for just one sensor you can get high
accuracy.. we had this in a 10k/year project and the accuracy is
+/- 5% humidity.
[end humidity sensors]
===
All the help you need, including close-up photos, will be found on my
Basic Soldering Guide, now part of the EE Virtual Library
http://www.epemag.wimborne.co.uk/solderfaq.htm
There is a text-only version at
ftp://ftp.epemag.wimborne.co.uk/pub/docs/solder.txt (21k)
Alan Winstanley - On-Line Editor email: alan@epemag.demon.co.uk
Everyday Practical Electronics Magazine My views are my views.
Wimborne, Dorset, Bh21 1PF, United Kingdom The Basic Soldering Guide
http://www.epemag.wimborne.co.uk - check the EPE Web Site!
===
Take a look at our archive of circuits. It has an FM transmitter circuit.
Also, while at our site, download the free reference software with 100
circuits, plans, etc. It also contains an FM transmitter circuit.
Damian Bonicatto
PTM
Creators of CyberCircuit and CyberCircuit Plus...a software encyclopedia of
electrical circuits, formulas, graphs charts, etc.
Try a FREE download at:
http://members.aol.com/cybercir/index.html
Material from earlier versions of this page has been 'polished' into more organised pages. Click here to visit them.
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Link to 'My Desk Pile' main page
Link to first page of electronics stuff
Link to a later page of 'Desk Pile' electronics stuff