Norbert's Electronics Projects Page

Last Update: November 6, 2017

1 Ethernet UTP tester circuit

A few years ago I installed a LAN in my house. Ran UTP CAT-5 cable all over the place. Of course, once you've run cable, you have to test it. Rather than shelling out the $100+ for a real tester, I decided to build a continuity tester of my own. It's only good for making sure you wire things up correctly, it won't check for frequency response / cross-talk / etc. Oh, by the way, you can test telephone cables with this circuit too. Well, here's the circuit ...
Ethernet UTP tester circuit

2 Serial Port Breakout Box

This project is used to enable a computer to control devices using my standard 5 pin DIN connector. In December 2007, I used it to interface a Commodore 64 to my Christmas Train Controls.

Manual for the Serial Port Breakout Box

Circuit Diagram

Serial Port Breakout Box

5 Pin DIN pin out for Train and Control Circuits

3 Home Monitoring System

This project is used to display the state of several sensors in our home. The system consists of up to 7 sensors (6 currently used);sensor interface units that translate the sensor waveform to a digital signal, including the alarm singal; a Sensor Hub that collects the sensor digital signals and sends them via RS-232, a multiplex output, or a parallel output to other units; Software running on a LINUX server for remote monitorin on any workstation; and a remote indicator using the multiplex output of the Sensor Hub. The current list of sensors are:

     Flooding Alarm: Utility Room
     Flooding Alarm: Laundry Room
     Clothes Washing Machine Status (on or off)
     Clothes Dryer Status (on or off)
     Garage Door Status (open or closed)
     Mailbox Status (time since last opened)

Circuit Diagrams

Circuit Diagram for New Washing Machine Current Sensor (We bought a new Washing Maching machine that has very unusual current characteristics that was causing the old current sensor to not function properly)

Circuit Diagram for Remote Display of Status

Sensor Hub with Sensor Interface Units

The Remote Display allows one to enable or silence an audible alarm for each sensor. It also counts (roughly) the number of hours since the mailbox has been opened (The counter resets after 8 hours or when manually reset)

Remote Display

The Flooding Sensor interface unit measures the resistance between the two conductors of the flooding sensor. When the resistance falls below a set value, the alarm sounds. As you can see, the sensor istself is of pretty simple construction.

Flooding Sensor

The Garage Door Sensor (as shown) was orignally a microswitch mounted so the garage door opener will close the switch (open the circuit) when the Garage Door is closed. Because of the relatively large motions and vibrations of the garage door opener, the microswitches tended to become damaged. I've since replaced the microswitch with a magnetic reed switch (such as used in alarm systems). It works much more reliably.

Garage Door Sensor

The Mailbox Sensor uses the circuit board from our old Stanley Garage Door Opener (circa 1985). After a little experimentation, I found a signal that corresponded to the the remote received signal. I added a connector to the board to tap this signal, and removed the various relays to reduce electricity consumption. Built an interface board to isolate the garage door opener card from the sensor interface. For the mailbox itself, I modified a remote by adding a connector to the push button, and connecting to it a magnetic reed switch. A magnet mounted on the Mailbox door activates the reed switch when the door is opened.
Mailbox Sensor Circuit

Mail Box Door Sensor (Modified Garage Door Opener underneath mailbox)

Mail Box Wireless Receiver

The Hub communicates with a LINUX based web server to generate a web page that refreshes itself to show the updated status.

Example of Web Page created by Web Server

The code for creating the Web Page is pretty basic. When I have the time, I hope to do it right ....

It does include some neat features like playing an audio file when the alarm is on.
It also can send an email (or text message) when an alarm is on
A log file can also be activiated to record the time when any sensor status changes

Source code for Web Server (Version 3.1 of Sept 2010)

4 Rain Barrel Pump Controller

This project is used to automatically turn a pump off when the water in a rain barrel reaches the low water point. It works by measuring the resistance of the water between two stainless steel bolts. The circuit uses positive feedback to implement a hysteresis so that the pump doesn't cycle on and off near the low water mark. When the pump is not being used, a bucket is inverted over the controller and pump to keep them dry during rain.

Rain Barrel Pump Controller

Directions for Operation

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