Thanks...yeah I know its pretty safe...did a wee bit of research first...and
then asked the dudes at the Electrical component shop (South Island
Component Center for those of you in CHCH) and they helped me heaps....so I
am armed and ready to (burn my house down..hehehe)
Thanks to all for the suggestions and help...will let you know how it
goes...ig I dont kill myself doing it..hehehe
Jeremy Coulter
Application Developer
Application Development Centre
Compaq Computer New Zealand Ltd.
Phone: 64 3 371 5724 (DD)
Fax: 64 3 371 5744
Cell: 021 2150435
E-mail: [EMAIL PROTECTED]
Private E-Mail: [EMAIL PROTECTED]
-----Original Message-----
From: Tony Blomfield [mailto:[EMAIL PROTECTED]]
Sent: Friday, May 21, 1999 11:11
To: Multiple recipients of list offtopic
Subject: RE: [DUG-OFFTOPIC]: Controlling external devices from PC
In my experiance you are perfectly safe to drive SS Relays direct. These
things use a MOSFet or HexFETS to handle the current, and as you say the
input side is optically coupled offering a high impedance low current
input, with fast switching, low internal resistance output, and total
I/O electrical isolation.
Because the internal inductance is low, there is usually no flyback
voltage to worry about anyway, and these are handled internally with
flyback diodes. It is perfectly normal in scientific instrumentation to
drive mains powered or High curent DC devices in this manner, so I fail
to see what the differance is with home projects provided you are neat
in your work, and observe obvious safty requirements (Fire and
Electrocution).
However, just how many devices do you intend to interface? You could use
the Handshake control lines of the Serial port or the Printer port, but
you are very limited in the number of devices you can control. Also, you
need to check out the drive requirements of your relays carefully
against the available drive from your LPT/Serial lines. You
are pretty soon going to run up against the wall here and this is where
the micro with appropriate output decoding becomes usefull.
To have one micro driving one relay just to get some buffering would be
pretty dumb.
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Jeremy Coulter
Sent: Friday, 21 May 1999 10:36
To: Multiple recipients of list offtopic
Subject: RE: [DUG-OFFTOPIC]: Controlling external devices from PC
Well I have seen these things that you can get in the states that
control 15
devices or something like that, that you can plu things like heaters or
tvs
or what ever into, and control them from you PC's Parrallel port...I
have
had mixed results with playing with devices I have made that are
controlled
via LPT prot in the past, But these wee black boxes from the stats, ONLY
run
on 117v ! so thats no good to me...and they are only about $200 US or
there
abouts.
I have a book called, Controlling Your World From The PC", and it says
there
are savety thinks you can to to protect your PC from being fried...like
using Solid State Relays, as they can deal with Spikes as they are
optical
etc.
Jeremy Coulter
Application Developer
Application Development Centre
Compaq Computer New Zealand Ltd.
Phone: 64 3 371 5724 (DD)
Fax: 64 3 371 5744
Cell: 021 2150435
E-mail: [EMAIL PROTECTED]
Private E-Mail: [EMAIL PROTECTED]
-----Original Message-----
From: Alistair George [mailto:[EMAIL PROTECTED]]
Sent: Friday, May 21, 1999 09:46
To: Multiple recipients of list offtopic
Subject: RE: [DUG-OFFTOPIC]: Controlling external devices from PC
Yes. I agree totally with Peter, Jeremy.
Depending on the situation it can be relatively easy to set one of these
up.
For instance, in our application (and Paul Lowman's various) we have
been
using a micro called and 8051 (variant) with reasonably low-cost
compilers
you can program these beasts in C, or if ur a masochist ASM and in this
family you can even reprogram the source code from a PC via the serial
port.
That particular variant has a code kernel which lets you do that, in the
event of remote location code alteration.
Depending on what you are doing of course; if expense and time is a
problem
you would be hard-pressed to better what Peter is talking about with the
'Stamp'. If you are going to manufacture plenty I would suggest the 8051
route. There is a plethoria of info on the net - I can send you some
urls.
To get up and running you would be looking at Programmer cost of about
$200,
a good C assembler (Hitech) for about $700. I could sell you one of my
emulators for about $200 (thats a bit you can plug into your PC and
debug
trace and operate ports (similar to running Delphi debug, but with
hardware
control as well). Cost of the 8051 micros for a 20k is about $18, for 2k
is
about $4. With 20k you can do a hellofalotof program.
Cheers,
Al+
> A 'safer' way would be to interface your computer to a microcontroller
via
> serial port, and have the microcontroller deal with the switching of
high
> current loads. This means if you screw up only the microcontroller
gets
> fried, rather than your expensive computer. You can get a neat little
> microcontroller from dick smith for $150.
>
> This approach also gives you the advantage of not having to have your
> computer on all the time. You can program the micro to do quite
complex
> programs - and not even need to talk to your computer. The micro I'm
> thinking of is the Basic Stamp 2, which I have been using for
> over a year in
> small robotic projects.
>
> There are much cheaper micro's, but they require expensive
> programmers, and
> are harder to program. The BS2 is hooked directly to your serial
> port, uses
> easy to learn Token Based Basic, and is pretty robust (I havn't
> broken mine
> yet dispite mistreating it quite a bit).
------------------------------------------------------------------------
---
New Zealand Delphi Users group - Offtopic List -
[EMAIL PROTECTED]
Website: http://www.delphi.org.nz
---------------------------------------------------------------------------
New Zealand Delphi Users group - Offtopic List - [EMAIL PROTECTED]
Website: http://www.delphi.org.nz
Jeremy Coulter.vcf
