David Connolly

Electronics have always been fascinating to me. Things that get my attention are clocks, lamps, motion activated devices, light activated devices, laser intruder alert systems,solar and wind power, voltage inversion and lots more. I was lucky enough to be born in 1957 which has allowed me to watch so much history as the years have passed. The NASA space program in the 1960s was so unbelievably exciting as they worked towards the goal of putting a man on the moon.

Interests: Astronomy, Astrophysics, Theoretical Physics, Technology, Solar Power, Retro-tech, General Science, Lock picking, Linux, SCUBA Diving, Mountain Climbing,

Location: Austin TX

Sep 102016

Do you ever use a transistor in an electronic project then pull all the components back off the breadboard and put them back in stock. And then when you’re ready to use them again you’re just not really sure it’s still in working condition. It’s a frustrating learning situation when building an electronic project and for one reason or another it just doesn’t work, and you’re not confident all your components are working as they should.

Well here’s a project you might find handy to have on your workbench. It’s a simple transistor tester and if you have a dead 9VDC battery lying around then that would be the perfect power source for this project.


  • LED
  • 10K ohm Resistor
  • 680 ohm Resistor
  • 180 ohm resistor
  • SPST tactile momentary button/switch
  • Breadboard
  • 3VDC – 9VDC power source
  • Transistor to test



Here is how you connect the components







Tester laid out on the breadboard.

Tester laid out on the breadboard.










Tester in action. Showing the NPN 2N2222 transistor is fully functional.

Tester in action. Showing the NPN 2N2222 transistor is fully functional.










Assorted button you can use.

Assorted buttons you can use.

Basic momentary tactile button is perfect for this project

Basic momentary tactile button is perfect for this project

Bottom view of NPN 2N2222 pins

Bottom view of NPN 2N2222 pins
















This project requires  less than $1 worth of components and can save you from much frustration. I hope you find it helpful. Now I need to make one that will test PNP transistors. So much to learn.

Happy electronic project building!



Sep 082016

If you’re looking for a robotics project to build. And if you want to be fun, quick, and easy this is the robot project for you. I found it at https://www.hackster.io/lovelyideas-in/arduino-remote-car-using-bluetooth-hc-05-android-app-control-3da97d  Mr. Jones Kys did a wonderful job developing this. Everything you need is available for download, including the Arduino sketch, schematic, and Android app.

Bill Of Materials:

  • Arduino – Uno,Nano, or Pro-Mini will work. Possibly others as well.
  • HC-05 Bluetooth module
  • Two DC motors and a chassis (you can be creative with the chassis)
  • L293D Dual H-Bridge motor driver
  • Power source (I used two 18650 Lithium Ion Rechargeable Batteries)
  • The Arduino IDE software (available for free at https://www.arduino.cc/en/Main/Software)
The rough prototype.

The rough prototype.

I put this together using an Arduino Pro-Mini and HC-05 Bluetooth module. An Arduino Nano would also work perfectly. I powered this using two Lithium Ion rechargeable batteries. I ran the hot lead to the RAW pin on the Arduino Pro-Mini. And the 5 volts for the Bluetooth module came from the VCC pin on the Arduino Pro-Mini. I am looking forward to cleaning it up as well as possibly including encoders on each wheel to solve the issue of one motor turning faster than the other, which causes the bot to veer off a straight line.


Motor with encoder wheel and two encoders.

Motor with encoder wheel and two encoders.










You can see in the picture what an encoder looks like and also pictured is the encoder wheel you mount to your axle that spins inside the two protrusions on the encoder. Also you might notice the 0.1uF capacitor I soldered between the two terminals on the motor. That cuts down on theEMF emissions from the motor that can interfere with the radio signal.

Here’s a short video of the robot/car in action.


You can download everything you need and check out the project at:


Jul 172016


Working with Level Shifterspresents400

Level shifters are a wonderful and very affordable solution when you have a situation where you have to interface a 3.3VDC and a 5VDC device. They are also called voltage shifters and they come in uni-direction versions where the signal only goes one way, bi-directional where signal goes both ways, direction controlled level shifters with a dedicated directional pin, logic level shifters that put logic functionality and voltage translation into a single design, and finally application specific level shifters .You will also find them in a variety of multi-channel types as well as bit rates. In this article we’ll cover the 5VDC/3.3VDC bi-directional 2 and 4 channel types available on Ebay for a very low cost and how to use them in your ingenious projects.

Step 1: Two channel level shifter
2 Channel Version


This was my first level shifter. I bought it from a seller on Ebay. When i bought I had not yet worked with level shifting so I did not notice the module was not marked to indicate which side was LV (low voltage) or HV (high voltage). Simply put you supply 5VDC and GND (ground) to one side of the module and 3.3VDC and GND to the other side. The first time i used it I was using a 3.3VDC ESP8266 to wirelessly control a 5 VDC servo. Without the shifter the ESP8266 would not boot up. Once I had the shifter in place it performed perfectly.

The markings that are on the module are:prefaced with an “A” on one side and “B” on the other.

  • AVCC (I soon figured out this was the 5VDC input)
  • ASCL – This seems to indicate the module is I2C compatible.
  • ASDA – In an I2C situation this would seem to be the SDA data signal connection
  • AGND – This pin goes to the ground bus

In this example I’m interfacing a 3.3VDC HC-06 bluetooth module with a 5VDC Arduino Pro Mini to turn on and off an LED using Putty on a BT equipped laptop.

Step 2: 3.3VDC HC-06 Bluetooth – 5VDC Arduino Pro Mini

LED Control Circuit

I also bought some 4 channel shifters and they are marked HV and LV which tells me which side should be connected to the 5VDC power and which gets the 3.3VDC power. They are also marked TX and RX but I disregarded that in this setup and I am having no problems TXing on the RXing channel. I’ve breadboarded a 3.3VDC HC-06 Bluetooth with a 5VDC Arduino Pro Mini. using I’m using PuTTY ( a free SSH and telnet client for Windows) on a bluetooth eqipped laptop to control the Arduino to turn on and off the LED. You can get a free copy of PuTTY at http://www.putty.org/

The Arduino Bluetooth LED control sketch is avalable @ http://volthauslab.com/sketchs/Bluetooth/bluetoothLEDcontrol.ino

Nov 082015

In our travels about the Internets we have came across many a helpful website. It is with much joy and satisfaction we share them with you now.


Electro Schematics Electro Schematics is a treasure trove of projects (1089 electronics projects and circuits) we are sure will lead you further down the hobby electronic rabbit hole.




allaboutcircuitsAll About Circuits One of the largest online electrical engineering communities. A positive, open community of electronics geeks that enjoy sharing knowledge and ideas.


Talking ElectronicsTalking Electronics – The legendary Aussie Colin Mitchell‘s website. This was what started it all for a generation of electronic hobbyists and future electronic engineers.


Duino RoboticsA good get started in robotics site. Lot’s of info including Arduino code for DIY obstacle avoidance robots. Links!






Instructables Instructables is a community driven website that has tutorials (ibles) and how-tos on anything you can imagine. Electronics is only a part of what is covered.



Electronics For UThe title kind of says it all. If it’s electronics, it’s here. I tend to agree. Based in India this website covers almost every aspect of electronics. It’s worth it to (free) register with them for total access.


letsmakerobotsLet’s Make Robots is a total robotic community. Registration with allows you to actively share projects, news, videos and more.



 Embedded LabEmbedded Lab: An online teaching laboratory for Microcontrollers and Embedded Systems. A very good website heavy on microcontroller use in many projects.



Electronics Hub

Electronics Hub has a large selection of projects, circuits, and information that will prove quite helpful to hobbyists.

TronixArduinos are the main focus at tronixstuff. In fact they have over 50 Arduino tutorials.


EEV blog

David L. Jones is an electronics design engineer based in Sydney Australia. He hosts the EEVblog, the world’s largest and most popular engineering video blog and Youtube channel. In each episode he shares some of his 20+ years experience in the electronics design industry in his unique non-scripted naturally enthusiastic and passionate style.


Sep 272015

DC Electric MotorDC Electric DIY Motor Project

Let’s build an electric motor. “An electric motor is an electrical machine that converts electrical energy into mechanical energy.”  We won’t go into exactly how the electricity makes this motor work because that would be a book all on its own, so let’s build this motor and have fun! To learn more about the technical knowledge of electric motors I suggest you start by reading the Wikipedia page.

Bill of Materials (BOM):

2 – Paper Clips
1 – Battery or power supply:  D cell, 9 volt, AA, 2 AA, benchtop power supply
1 – Bread Board, card board, piece of wood to mount the motor or rubber bands to hold paper clips to end of D cell battery
1 – Magnet – Can be a bar, circular, or just about any shape. I used 2 – 13mm diameter Neodymium magnets, and 1 5mm diameter magnet stacked one on top of the other. I drilled a hole in the board to prevent the magnets from snapping to the paperclip axles. These rare earth magnets are extremely powerful. Our motor with these magnets turns at 180 RPM and seems to have much more power than you would get using plain ceramic magnets.
1 – Magnet Wire 22 AWG. It is a lacquer coated copper wire. You can try using insulated wire but your results will probably not be as good as you would get using the proper wire.

Project parts







Building Instructions:

1. Wind the 20 AWG magnet wire into a 20mm circle, making about 12-15 loops. It helps to wrap the wire around a cylinder of some sort to get better results. The coil you have just made is called a rotor.  You want to have a lead coming from each side of the coil about 20mm in length.
Rotor coil





2. Holding the coil upright put one of the leads on a flat surface.  Using a razor knife or a small piece of 220 sandpaper, remove the lacquer coating from only the very top surface of the wire.  Leave the coating intact on the sides and bottom. Remove the lacquer from the wire from the very end to right up to where the lead meets the rotor.
3. Remove the lacquer from the other lead completely, 360 degrees around. Again from the tip of the lead all the way to where it meets the rotor.
Base with axel supports







4. Straighten your paperclips and make an axle rest at one end. Needle nosed pliers are very handy for this part of the build. You should make them about 25mm long. Place your axles 60mm apart.

Axel support





5. Place your magnet in the center between your axles. Hot glue is good to prevent the magnets from snapping to your metal axles. I drilled a deep hole that could hold all three of my magnets. Using the rare earth magnets which have a very powerful attraction, drilling a hole in your base is a good way to prevent your magnets from snapping over onto your paperclip rotor supports.
6. You can also drill a very small hole in the base to place your axles into for a strong motor. You can also thumbtack them down, or use any other method you can think of, you just want them solid enough to stand upright.







7. Now set the rotor onto the paperclip axles.  You want your rotor directly over the magnets and close to them as well.  You can place cotton from a cotton ball into the hole to raise the magnets, or any thing that will shim them to just below the path of the rotor as it spins.


8. Connect your power to your rotor supports by whatever means you have available. If you’re using a benchtop power supply you can connect your alligator clips to the axles. That is a great way to adjust the height of your axles also, letting the alligator clips hold the paperclips at the right height. If you’re using a D cell battery you can stand an axle at each end of the battery and wrap the rubber band around the entire setup. I don’t suggest doing it that way but it does work.
9. Turn on your power supply at 3.3 volts to begin with and increase if needed. Or connect your battery. The neodymium magnet motor sometimes started spinning on its own as soon as the power was turned on. This happened when sending 5v to the motor. You probably will have to bump the rotor slightly to get it started. You should see which direction it has a tendency to spin and that is the direction you want to push the rotor to start it spinning.


In this video the motor is powered by two AA rechargeable batteries that supply 1.2v and 2700mA each. Watch it go!

Desktop computer power supply modified to work as work bench power supply.

Desktop computer power supply modified to work as work bench power supply.


10. If all is well you should have it running now. Usually some fine tuning is needed to get things working perfectly. Cutting a small disc from a business card and placing on the rotor leads can prevent the rotor from moving laterally and falling off the axle supports.

If your motor still does not run, double check your work! Make sure the lacquer coating was removed exactly as instructed.
When you’re finished turn off the power and put away your tools, any scraps of wire that may have fallen on the floor, etc. A clean and orderly workshop is a safe workshop. Also you don’t want to leave a mess for someone else to clean up. The electronic hobby is a great way to learn, have fun, and make wonderful things that will improve your quality of life. It also is a great way to share your time with your children. This is a fantastic hobby so treat it with respect and be safe. We hope you have enjoyed creating this motor, and reading this tutorial as much as we have had making it. Putting this together for you and spreading the  knowledge of the hobby of electronics has been a privilege.
Thank you.
Volthaus Electronics Laboratory
Sept. 27, 2015









Sep 122015

Once a month or so the Volthaus Electronics Laboratory  Team will make the rounds of various thrift stores (i.e. Goodwill, etc.). Recently while browsing we found two Altec-Lansing Powered Sub-Woofers. One was priced @ $5USD and the other one was $10USD.


altec-lansing-system They were originally a part of a 5.1 computer speaker system but when found, it was the sub-woofers only. They were purchased and brought back to the lab for tear down. They have proven to be loaded with high quality components. The first thing found of course were the speakers. The smaller of the two was 4in and the larger was a 6in and they were obviously well made.
Inside each one was a very larger number of components such as Samxon capacitors in a variety of values,  several TDA Op-Amps (TDA7265, TDA7294, TDA7482, etc.), hardware, and each one had an AC transformer featuring multiple VCT voltages.  Just guessing, somewhere in the neighborhood of $100 worth of parts per sub-woofer were salvaged.

The only problem with these powered sub-woofers were they were missing the satellite speakers, one of which in each system contains the controls. All in all an excellent find of components at a truly rock bottom price.
And everything recovered from them works perfectly. Possible future plans call for the cabinets, speakers, and some of the other salvaged parts to be used in two projects. The projects are high wattage, lab built guitar and bass amps. The second powered sub woofer (100 watt) contained a massive toroidal  transformer.toroid

These transformers alone are worth anywhere from $25USD to $50USD or more. Which brings us to the question:

What components should you take the time to salvage?

1. Knobs

Knobs average in price from .50 centsUSD for a functional but not very attractive knob to $1.50USD for a Marshall amplifier style. When you see a quality knob, grab
it, you will be so glad you did! It takes only seconds to remove a knobs and it is so helpful when building a project you can just reach into your storage drawers and get one, put it on and proceed with your masterwork.

2. Switches

The switch is one type of electronic component that is ever rarely discontinued. Through the years, I’ve found switches on rack mount audio gear, mixers (goldmines for knobs), ancient VCRs (miniature push-buttons off their PCBs), from multi-function printers.
And of course from amplifiers. I go for the input selection multi-pole rotary encoder switch. I’ve found them in abandoned cars dashboards.
Switches come in all shapes and sizes and is one electronic component that doesn’t go out of date.

3. Wire (stranded and solid), Nuts & Bolts, etc.

A fried desktop computer power supply can give you plenty of stranded copper wire. Even the case it comes in can be re-purposed as a project enclosure. And the hardware that holds everything in place can, and will become useful. An old computer is a treasure trove of bolts, stand-offs, etc. Everything you salvage from one is less that goes into the dumpster. Good for you and good for the planet. And your wallet.

4. Fuses

A glass fuse and its fuse holder are just as useful today as it was years ago.
You can find fuses and their holders from all sorts of equipment.
If the fuse holder is an inline type  (The little two piece holder in the voltage supply wire: think CB radio, radar detector or 8-track player: Yes i said 8-track player) or easily removed chassis mount design.
You can also obtain very useful fusible links from car fuse and relay boxes, and much industrial equipment contains re-settable circuit breakers.
I have also salvaged the two different sizes of blade fuse used in vehicles. I have an old commercial prototype 12v to 110v inverter and they soldered the blade fuse directly to the PCB. Once bypassed (it was easier to leave it in place and solder in a new one) the inverter works perfectly.
It’s not at all hard to collect enough fuses so you’ll never need to visit AutoZone to buy one again, or wait while an affordable one is shipped to you from China.

5. Relays

Relays are very useful, rugged (basically impossible to blow up), universal within voltage and current restraints, and easy to wire into place. And their usefulness is increasing. Via the Internet of Things so many appliances can be controlled through either your home network or the internet. An enormous range of equipment and appliances have relays inside which you can easily collect one from even moderately complex bits of gear you salvage.
Relays (and many other parts) can be removed from PC boards quickly and effortlessly by using a heat gun aimed at the solder side of the board and plucking out the relays with pliers. I remember picking up an ABS (anti-lock braking) controller from a car and realizing it contained no less than six small, high current 12V relays.

6. Ultrasonic sensors

This is a fairly recent development in automotive salvage and a set of four removed from a automobile at a salvage yard can cost you around $30USD. But they are quite a bit more powerful than an Ultrasonic Ranging Module HC-SR04 and all-weather also.

7. LEDs

The LED has become so low in price that salvaging them may seem like a waste of time, but if it is something special like an RGB for instance I will definitely take the time to remove it and deposit it into my container marked “exotic LEDS”.
It’s easy to salvage LEDs that are special to you for some reason. Those with odd lens, unusual shapes (I love those), and LEDs in shades of colors you might not normally see. And using the heatgun method mentioned earlier you can quickly recover handfuls of LEDs so go get em’. They are free.

8. Plugs and Sockets

While I’m not a huge fan of trying to stock up on recovered plugs, sockets, etc. there are a few exceptions to that rule. The RCA female sockets are particularly useful when building stereo amplifiers. Also another socket (jack) I will go after is the female 1/4in phone jack you find on instrument amplifiers and the instruments themselves. They cost an arm and a leg brand new so I get those every chance I get.

9. Heatsinks

You should visit my heatsink museum if you ever get the chance. Heatsinks are found in discarded computers in a huge range of sizes. From small ones that cover the chipsets to large heatsinks that are attached to the CPUs And there are huge ones in power supplies and in audio amplifiers. If you’re building projects it really pays to have a large variety of heatsinks on hand because many of the modules you attach to Arduinos and other microcontrollers need a heatsink if you want them to operate reliably.  ENC28J60_heatsink
Take my ENC28J60 network adapter module for example. Many people swear they can only get them to work when pumping 5v into them. I tried and it did work but the ENC28J60 IC became so hot I am sure you could have easily fried and egg with that amount of heat. And in no time at all it started acting unreliable. Now I have had great success running mine at 3.3v. There is a DHT22 sensor connected to an Arduino Nano in the laboratory that is running a webserver sketch, and it has been operating for at least 6 months now, day and night, week after week with no problems. Check it out at  http://volthauslab.ddns.net/ It runs great for me on 3.3v but it still gets quite hot and I have heard other people say it worked for them a short while then quit and I’m positive heat is playing a major part in its lack of reliability. I made the holding clip from a basic paperclip and i also added a dab of thermal paste between the sink and the IC.

10. Motors

Motors are everywhere and you should not be letting a single one get away. You can find motors of two types in almost every malfunctioning CD or DVD drive. The rotary motor that spins the disc plus a neat little worm gear stepper motor. And you can also find stepper motors in printers as well. If you want the large motors you can salvage them from home appliances like dryers and washing machines. Those are just a little out of our league (currently that is).

Good luck because you’re going to need it once you begin to get your collection together. Getting organized and staying that way is a real challenge (fun). And we didn’t even cover what you can pull out of old CRT televisions and other things, but I think this is a good start. Have fun, be safe, save money and build wonderfully fascinating things!


Aug 312015

This night light does not begin glowing until the ambient light in the room is very dim. Others begin glowing when the light in the room is still fairly bright. If your night light comes on when the light in the room is still bright you’re going to be wasting a lot of the electricity in your battery. Another feature is the use of the 9 volt battery using the built-in 5 volt regulated power supply.


The completed circuit on bread board with LM7805 based 9v to 5v voltage regulator









Step 1: What You Will Need


  • SPST on/off switch (optional)
  • LM7805 Voltage Regulator
  • 0.33uF ceramic capacitor
  • 0.1uF ceramic capacitor
  • 820R ohm axial-lead resistor
  • 100k axial-lead resistor
  • LED – Bright red is easier on sleepy eyes but white will probably be brighter
  • GL5528 LDR: also known as a Photocell – Photo Resistor – Light Dependent Resistor
    Bright Resistance (10Lux) (KΩ): 10-20Dark Resistance (MΩ): 1
  • 9 volt battery snap
  • 9 volt battery
  • Breadboard for testing
    a 2N2222 NPN transistor will
    work in this circuit just as well as the 2N3904. The main difference
    between the two transistors is the amount of amperage they can handle.
    If you’d like to see a page comparing the two in depth visit:2N3904 vs 2N2222

Step 2: The Circuit Schematic

schematicThis is the complete circuit. I used CadSoft’s Eagle schematic design software and the LDR symbol is a little different from the LDR symbols I’ve seen on other schematics. Since my voltage to LED1 is 5 volts and that particular LED is rated at 2.0 – 2.4 volts and 18 to 20 mA you could place a resistor (R1) as low as 150 ohms, if I use 2.2 volts as my estimated voltage drop in the equation. It’s the R2 100k resistor that controls how much ambient light will set off the night light. If you replace it with a lower value resistor (for example a 47K resistor) the LED will glow even though the room light is still plenty bright enough for you see around the room.

Step 3: The Voltage Regulator

I built the voltage regulator first and then tested it to make sure it was actually putting out 5 volts. As the 9 volt drains it will maintain the correct voltage this night light needs to operate correctly. I really think it should be able to go for quite some time before the battery will need to be replaced.

Step 4: The Completed Circuit

Here’s a close-up of the completed circuit. You can see it’s really very simple. In the picture where the LED is lit I have placed a Sharpy pen cap over the LDR to put it in complete darkness. I plan to make some birthday and Christmas gifts using this circuit. Maybe find a Statue of Liberty model where the LED can be placed in the torch Lady Liberty is hoisting up in the air. Another couple of ideas I’ve had are to place the night light in a tiny house so the glow comes through the windows, or a little campsite with the LED in the campfire.



Aug 132015


Electronic circuits don’t come much simpler than this.



BOM: (bill of materials)

  • PIR – The Passive Infrared Sensor – Buy Now
  • Buzzer – The buzzer that sounds when the sensor detects motion – Buy Now
  • 9 volt battery and battery clip with leads
  • Jumper wires to complete the circuit
  • Optional – Solderless Breadboard – Buy Now
This is the wiring of the project.

This is the wiring of the project.








Connect the positive lead of the 9 volt battery to the positive rail of the breadboard or the power pin of the PIR module and the negative lead to the negative rail or the ground pin of the module. If using the breadboard connect the positive and negative pins of the PIR module to the corresponding rails of the breadboard.

Connect the positive pin on the buzzer to the High/Low Output pin of the PIR module and the ground pin to the negative rail of the breadboard or connect it to the negative lead of the battery to complete the circuit.

Congratulations you now have a motion activated alarm!

PIR module information: PIR module datasheet

Buy the parts for this project!
Solderless Breadboard – PIR module – Buzzer

Mini Circuit Experiment Solderless Breadboard 400 Tie Points Contact

Mini Circuit Experiment Solderless Breadboard 400 Tie Points Contact

Infrared sensor with control circuit board

Infrared sensor with control circuit board

Convenient for connecting

Convenient for connecting