Contact closure

Have a question or want to start a discussion? Post it! No Registration Necessary.  Now with pictures!

Threaded View
I have this crazy idea that...

1. I can use contact closure from a Home Depot style motion sensing
light fixture to provide a 120vac relay with contact closure-not

2. With that contact closure on the relay I can use ________________
to inform a program running on my computer that the contact closure
has occurred. It doesn't have to be wireless. It could be serial
(distance ~60' to PC).

3. With contact closure sensed at the computer, a program running on
the computer would sense the signal, and act. I can write for Linux or
Windows, with .NET the preferred solution due to graphics for

I want to trigger actions on my audio port on the computer based on an
interim program that is listening for a signal/state to occur. Simple.

There are Rube Goldberg solutions out there with wireless, web, etc.
but this really doesn't need to be. Most every sstem-including the
risky/noisy X10 are designed to _send_ contact closures, not _receive_

- I can solder a relay into a disassembled driveway motion detector in
2 minutes.
- I can run a contact closed pair to the PC.
- I _cannot_ convert that contact closure right next to the PC into a
signal that a running program/daemon can use as a trigger to act upon.

How can I convert a contact closure into a signal that a running
program can use?



Re: Contact closure
<bogusexception> wrote:
Quoted text here. Click to load it

Here's one of several products that you could use to make the connection
between a dry contact and your PC.

That said, you might want to consider an alternate approach if the overall
system is to be responsible for the security of the property.  There are
simple to install alarms, both wired and wireless, which can provide security
and/or varying degrees of lighting and automation control available for DIY.
Models like Napco's P9600 and P3200 systems can include an RS-232 port with
real-time status reports to the PC.

I'm a bit biased in this area since I sell Napco, but they do make reliable
systems.  ELK Products and a few others also offer ways to integrate their
systems with a PC.  Elk is pricier than Napco but it's a full-blown home
automation system whereas Napco is an alarm with HA integration options.


Robert L Bass

Bass Home Electronics
DIY Alarm and Home Automation Store
Sales & Service 941-870-2310
Fax 941-870-3252

Re: Contact closure

Thanks for writing.

Quoted text here. Click to load it

This is $89, and way outside the budget.

Quoted text here. Click to load it

Well, that might help in certain scenarios, but mine is not security.
My purpose is to create a "mosquito" (see: =
I have a ..."neighbor" problem. In short, they are up all night
partying outside our bedroom window.

So I have all the components, except for that one link that will allow
a program of my own design on a PC to sense/react to a contact closure
right next to the computer.

Thanks for the advice, and any other advice that comes my way!


Re: Contact closure
Quoted text here. Click to load it

You have a cheap and dirty way of doing this...

if you have a simple joystick connected to your computer you could use the
trigger button to trig a action in a software..

cheap usb joystick are sold below 5$

use a 110 volt relay connected in place if the 110 volt light bulb in the
detector system and use one of the contact of the relay (n.o.) as the signal
to close the trigger button in the joystick i am sure you can find ready
made routine in .net to monitor a joystick...


Re: Contact closure

This is fiendishly simple... Perfect!

I was already doing all the rest (110vac relay and all), but shorting
a 'Fire' button is really clever. Nobody else thought of that! :)


Quoted text here. Click to load it

Re: Contact closure
There a re much more way of doing this..

on a old pc, using the Lpt1 port printer ready input could alos do th

thye same on the serial 1 port terminal ready pin could also be used..

I didnt put it on the first post cause you want to use your standart pc to
do the job...and most new pc dont have those port anymore..

de discussion :
Quoted text here. Click to load it


Re: Contact closure

Thanks for writing.

Here is what things look like so far (as good as text can do)...


Wall timer 1 (~$5)
- Applies power to motion sensor (below) during desired hours of

Motion sensor (standard driveway type (~$11))
- Senses motion up in the attic through vents
- Provides 120vac when "tripped"

120vac DPDT relay (~$2)
- Uses 120vac from motion sensor above to provide contact closure

Cat 5 cable to basement (one pair soldered to relay above, carrying no
voltage contact closure to basement)
- I could use the other 3 pairs in a similar fashion in future


USB Joystick ($7)
- Torn apart to solder the Cat 5 pair above to one of the buttons'

- Existing Win 2003 Server box acting as file and VM server for home
data center
- Hosts a V.NET application
- Has audio/line out hooked up to Crown D-150A II (150watts/channel
boat anchor), with attentuation adjustments on front of chassis

VB.NET application
- Will be monitoring the USB joystick for signal that is recognized as
a button press, which is really contact closure from the attic via the
Cat 5 above.
- Brings up and down the audio level so the chosen tone(s) is/are
brought up and down very slowly. The idea is to be covert and not
- Can choose random MP3s (created with various tone/signal generators
(like Visual Analyzer) randomly, based on time of day, on demand, etc.

Wall timer 2
- Powers up the Crown audio amplifier during desired hours of
operation (too expensive otherwise)
- Acts as a second assurance that tones not generated outside desired
time of day range

Audio amplifier (25 years old) Crown D-150A II
- The definition of overkill-you can weld with this thing
- Takes audio in from computer, attentuates it per knobs on front, and
supplies speaker output

Speaker wire
- Run up to the basement, where the speakers are

Attic (again):

- At and under 1uf to act as both tweeter protection and provide HPF

Speakers (4 various for ~$10)
- 50w capacity and higher, avoiding accidental damage
- Various directional and unidirectional designs
- Soldered together in series/parallel (lower ohms =3D higher
capacitance needed for HPF)


IR Camera ($250) IP wireless w/pan/tilt on first floor
- Have already placed a similarly shaped/colored object where camera
will be, as it will be visible
- IP wireless will be available in basement control center

Microphone (headset?)
- Will need to stick a microphone outside to hook up to the PC
spectrum analyzer
- Will provide relative level measurements (signal to ambient)
- Used to determine how loud signals are when detected, using this
threshold to work under

I think that is it.

I want to experiment with varying/cycling tone frequency and
intensity, as well as combining frequencies close to each other and
their harmonics. Unlike my laptop's amplifier (10% THD), the Crown is
at 0.001% THD, which means there will be no unwanted lower harmonics
giving the device/system away.

So there you have it!


Quoted text here. Click to load it

Re: Contact closure
"Petem" wrote:
Quoted text here. Click to load it



Robert L Bass

Bass Home Electronics
DIY Alarm and Home Automation Store
Sales & Service 941-870-2310
Fax 941-870-3252

Re: Contact closure
The joysticks came in today!

I wonder if they are from the U.S., though... The first feature is:

"Exquisite design and comfortable handle make you handy to play;"

Who doesn't want some of that?!


Site Timeline