A few weeks ago I reignited my electronics hobby by purchasing a couple of “put it together kits” that were on clearance at RadioShack. The first kit I tackled was the Velleman K8048 PIC Programmer & Experiment Board.
Velleman K8048 PIC Programmer & Experiment
I’ve played with microcontrollers/PICs in the past, specifically the Parallax BASIC Stamp 2.
Its an exxcellent kit for the novice at a reasonable price.
Parrallex BASIC Stamp Activity Kit
Soldering the components on the Velleman K8048 board isn’t that difficult. If you don’t have experience soldering I highly recommend that you watch a few YouTube videos and practice with a few wires.
TIP: Solder likes to flow toward the hottest area.
After I had completed the kit I went to my drawer of power supplies to locate a 12v unregulated or 15v regulated DC output power supply. Out of the 20 or so power supplies none of them met the requirements. I figured I could either buy a new one or have some fun in building a variable output power supply.
My next posting will be part one of several covering my experiences with designing and building my power supply.
QuantAsylum QA 100 Digital Oscilloscope
My personal electronics projects have progressed to the point where I need to use an oscilloscope to not only diagnose my circuits but also to further my education.
My research led me to a series of comments left on SparkFun. After looking at various other digital oscilloscopes I decided to give this one a try. This one appeared to be good enough to cover majority of my near future projects at a reasonable cost.
NOTE: This oscilloscope is also my first personal scope and using a digital one. I had used various analog ones in high school and college.
I’ll be posting more about the scope as I use it with my projects. I’ll start with some very basic uses during my power supply project.
Additional information on the QuantAsylum QA 100 Digital Oscilloscope can be found here.
<post photo of setup>
My previous posting/project, PIC Programmer & Experiment Board, created the opportunity to build my own power supply. A Google search will turn up many design variations, but the most popular is to use an AC transformer, 4 diodes or a full rectifier, capacitors, resister, fuse, and a switch.
As I was testing the transformer and full wave rectifier I noticed a significant difference between the AC voltage output from the transformer and the DC voltage output from the rectifier. It was large enough that it made me want to investigate.
Radio Shack – 25.2V Center Tap 2.0A Heavy-Duty Chassis-Mount Transformer with Lead
Model: 273-1512| Catalog #: 273-1512
You will often see transformers with 2 input lines and 3 output lines like this one. The voltage between both yellow lines for this model will peak at approx. 25.2V up to a certain amperage. The voltage between the center tap (CT), which is the black line, and one of the yellow lines will be at approx half (12.6V) of the full capacity (25.2V). This is because the CT is a line from the middle windings of the transformer.
Transformer Voltage Readings – From Center Tap
<picture of voltage>
Notice the multimeter voltage reading of 13.87 AC and the oscilloscope’s peak voltage reading of 18.7 AC (peak to peak = 37.4). How can this be?
Turns out most multimeters report the root mean square (RMS) of AC voltage. The accuracy of the reading is highly dependent on the circuitry of the multimeter and the wave being measured. The higher-end models will have the ability to sample more frequently thus provide more data to calculate RMS. RMS also represents the DC voltage equivalent of the AC voltage that delivers the same energy.
This year for our Halloween display I purchased a fogger at my local Lowe’s store. It worked exceptionally well. My only complaint was it didn’t automatically produce fog. It required someone to manually operate a rocker switch.
The existing hand control is 115v AC based. The green light indicates the fogger is ready and the red rocker switch sends power to the fogger’s pump and produces fog.
The main concern is to isolate the 115v AC from the lower voltage circuitry both for the indicator and to drive the fogger.
I chose to use the H11AA1 Optocoupler to handle the indication that the fogger is ready (Green Light). The H11AA1 is designed to accept AC on one side (pin 1 and 2) and DC on the other (B,C,E). When the AC side is hot two tiny LEDs inside the chip will turn on. The DC side has a photodiode that will detect the light and allow DC current and voltage to flow via pins B, C, and E.
I chose to use a mechanical relay to handle driving the fogger to produce fog.
Around 1987, give or take a year, I got a similar one for Christmas. I’m not sure if I had a Gakken, Skilcraft or a Tron Link. I also don’t recall the version. I’m pretty sure it had to be either the EX-100 or below. (image found here)
What I can I say, being around the Apple ][ plus and wondering what those circuit boards captured my interest. It also helped that during this time I was watching shows that incorporated modern to futuristic technology: Superman III, The Wiz Kids and my all time favorite, WarGames, used computers, Small Wonder used an android, Knight Rider had KITT. I can’t forget Star Wars and its robots. All of these and more influenced me.
I have no idea how I articulated this want on my Christmas list that year. I’m pretty sure it was 1987 because that Christmas my sister got an interactive talking Juile doll (to this day that doll is creepy cool). I do remember opening up the present and immediately wanting to play with it. I remember my Aunt Sandy and Uncle Ed helping me with it; none of us really understood what we were doing. I remember trying out the lie detector tester and it being such a disappointment. We could tell it truths all day long and it’d flag it as a potential lie.
Overall, it was a neat kit. I was definitely interested and wanted to learn but I think my interests fell into the crack. I wasn’t old enough to demand my parent to help me find someone that could help explain the experiments nor was I old enough to be able to figure it out on my own. Today when I read about Steve Wozniak and other early Silicon Valley kids I read in envy. Why? Because they access to people all over their neighborhoods who knew a thing or two about electronics. I hit my maximum level of frustration with electronics with this kit and moved on. I am thankful that my parents did what they could and at least gave me a shot at learning electronics with this kit.
Training kit with a fully working Allen Bradley Micrologix 1100 PLC
My interests in electronics was rekindled in 2010 while I was working on a software project for a waste water company out of Charleston, South Carolina. That project required me to quickly learn about Programmable Logic Controllers (PLCs). In fact I purchased an excellent complete Allen Bradley MicroLogix training kit off of ebay from plc_trainer aka Ind-Concepts. Additionally I purchased a used Allen Bradley analog module off of ebay for the PLC.
While I was working on the waste water project I also purchased a Parallax BASIC Stamp Kit. More recently I’ve purchased a RaspberryPi Model B and an Arduino Uno.