Dave grabs a few junkbox parts and builds a useful constant current load for switch mode power supply, battery testing, and other applications.
EEVblog #102 – DIY Constant Current Dummy Load for Power Supply and Battery Testing - [Link]
In this episode Shahriar explores the world of filters! Starting from a simple lumped RC filter, he briefly covers the theory before moving onto measurement techniques. The bandwidth of the filter is verified experimentally in the time domain. A more complex RLC band-stop filter is also demonstrated with a tune-able inductor which is measured using an RLC meter. Using a Rigol spectrum analyzer with built in tracking generator and an active probe, the frequency response of the filter is measured. Several other packaged filters are also demonstrated and a microwave band-pass filter is disassembled to reveal its internal construction.
Tutorial on Passive Filters, Data Transmission and Equalization - [Link]
Dave explains, shows, and measures a potentially big trap with using high value ceramic capacitors. Is your 10uF capacitor really 10uF in your circuit? You might be shocked! Those humble X7R caps you think are a “stable” dielectric? think again… Class II and above ceramic capacitors can vary their capacitance drastically with DC bias voltage level and also the applied AC voltage.
EEVblog #626 – Ceramic Capacitor Voltage Dependency - [Link]
In this episode Shahriar presents a tutorial on the design and characterization of a single-stage low-noise bipolar amplifier suitable for audio applications. Given a set of specifications, a common-emitter topology is investigated. The circuit employs a beta-insensitive biasing scheme which is simultaneously optimized for maximum output swing. The small-signal gain of the circuit is calculated and the bandwidth is set for audio frequencies. A non-inverting operational amplifier is used as a second stage to achieve the desired overall gain. The circuit is assembled on a breadboard where the gain and bandwidth are measured and compared with design specifications. As the final experiment, the circuit is used to amplify signals from a microphone.
Tutorial on the Theory, Design and Characterization of a Single Transistor Bipolar Amplifier - [Link]
This video shows one method I use to wind toroidal inductors and transformers. The real trick is often how to hold the toroid core while doing the winding of the wire. The plastic toroid fixture shown is available from http://www.qrpme.com. I also give a few details on how to strip the enamel insulation, and then test the inductor when it is complete. There are many, many useful websites that contain toroid data, including composition, type, size, materials, winding factors, calculators, and more
How to wind a toroid inductor - [Link]
Dave tears down Sony’s first digital camera that used removable media, a 3.5″ floppy drive! The 640×480 resolution 0.3Mpixel 1997 vintage Sony Mavica MVC-FD7
EEVblog #625 – Retro Teardown: Sony’s First Digital Camera - [Link]
Ben is always looking for new tools and processes to help with all the projects he builds. He’s got a CNC mill, laser cutter, and a 3-D printer, but hasn’t found a way to whip up a PCB at his shop. He’s hand wired many circuits, but this can be tedious. He’s designed PCBs in Eagle and sent them off for production at a board house, but this doesn’t help when he wants a PCB the same day. In this episode, Ben experiments with three methods of PCB etching and shares the results.
Let’s Try PCB Etching! - [Link]
mjlorton @ youtube.com :
In this T4D (Tip or Thought for the Day…or just general chit chat) I give an initial demo / overview the the Fluke Connect equipment and Application. There seem to be some bugs / issues that still need to be worked out and Fluke are working on this. There may also be issues with the way I’m using the App…I’ll follow-up with a full review once this is all resolved.
T4D #103 – Fluke Connect Demo…and Chit Chat - [Link]
Original Apple 1 setup – demo of a working piece of history
This is one of 6 known working original Apple 1 personal computers from 1976. There were about 200 Apple 1 ever built and 43 units are identified to exist to date (08.2012). This Apple 1 had been originally restored and framed in 1993 by an Apple enthusiast. I restored this machine in 2012 to fully working condition (there was a faulty PROM) and attached an ASCII keyboard, monitor, power supply and an ACI (Cassette Interface). In the demo the machine executes some test programs and loads from cassette BASIC and a graphics demo.
The original Apple 1 came only as ready built motherboard: there was no keyboard, no case, no monitor and no power supply included. The buyer/user had to find and attach the peripherals himself.
The machine is pretty solid now – I booted this A1 more than 50 times in the last 2 weeks and it worked flawlessly.
Original Apple 1 setup – demo of a working piece of history - [Link]