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14 Posts authored by: Jan Cumps
On many Ethernet devices, you find magnetics - a transformer - as part of the physical layer.     The example above is from a TI TM4C launchpad. It looks like a solid block - like a silicon package.   I have a defect launchpad so I scavenged some parts. To my surprise, this is how the transformer looks like from the underside:     Surprisingly old school.   Supplier's schematic: Pulse HX1198FNL ...
I learned a trick from w2aew: how to measure current if you don't have a current probe. He's using a N-channel JFET as example. I adapted it to a P-channel type - the J176. This second post is the practical part. No talk and simulation. A real circuit real measurements. Read Measure JFET drain current with a current mirror for schematics and approach.   Building the Circuit  This is extremely easy. Only four components are needed. The  NPN transistors in the current mirro ...
I learned a trick from w2aew: how to measure current if you don't have a current probe. He's using a N-channel JFET as example. I adapted it to a P-channel type - the J176. w2aew describes this in a video. He also published the notes. Follow and understand that first, because I will focus on translating this to a P-channel circuit.     Current mirror  This is a nice trick to measure the current in a component if you don't have a sensitive current probe. It's not perfect, but ...
I reviewed an analog small signal switch in post 1: Simple analog JFET switch - part 1: schema, simulate and test. Here I'm checking what the limits are - the small linear part of the operational region where the P-channel JFET acts as a resistor. The circuit is published on neatcircuits.com   JFETs are linear for small signals. The schema here is for a consumer audio signal level, and that signal fits in that range for the J176 that I'm using. source: wikipedia   source: w2 ...
A simple low signal / audio "soft" switch with a p-channel JFET. It's very easy to make, with common components. Low power. The circuit is published on neatcircuits.com   I've ordered a set of transistors to play with. One of them is a ON Semiconductor (Fairchild) J176. This is a small signal P-channel JFET, designed for analog switching.   Let's first look at the circuit in the DC domain, with the switch open. Both drain and source are kept to ground by the 330K resistorsat in ...
I'm checking if I can use Doxygen to create documentation for the electronic load firmware. Doxygen is an application that can generate documentation based on declarations and comments in the source code. The eLoad firmware uses an API style that should easily adapt to Doxygen's way of working. The goal of this post is to get Doxygen utilities set up in Eclipse, document a first function and generate HTM documentation.   I used this document to set up Doxygen and integrate it in Eclips ...
  This is going to be a short article, because the activity is identical to Firmware Release with GitHub: Branch, Issue, Pull Request and Project support , but the other way around.   When creating a release, you merge the development code into the official master. But here,  after finishing a hot-fix, you merge the production changes (fixed code) with the ongoing project.   This time, I'll just use Git to merge the code, and GitHub to submit the pull request. Without pro ...
  So (lets simulate that) my last release created a production issue. The SCPI interpretor times out regularly, when used from one of the available PC clients. Maybe the job optimisation in the ADC task takes away free time from the UART RTOS task? It's a simulation for the purpose if this blog. This didn't (but could) really happen.     Goal: fix a bug in production code - master branch use the Eclipse Git plugin to manage the development (I try to introduce something new ...
  Scenario: Developments for current cycle are finished (by the developer. That's me) and are available in my repo's development branch. All that code has already been tested, built (by the developer. That's me). All code has been reviewed and accepted, as part of the development cycle (by the development branch owner. That's me). Release manager (hey, that's me too) now has the task to collect all development and integrate it into the release. That's the master branch.   Tools I ...
  A possible strategy for using GIT and working with branches. part 2: bug fixes on the released code     Fixing Bugs in Released Code while Development is Going On  This is a common challenge in for any project that has active development while there is a supported version out there. How do I fix bugs in my released code - and avoid that the fix is overwritten once the development of new features is complete?   In part 1 I reviewed a branch strategy for working ...
  A possible strategy for using GIT and working with branches. In this part 1: working on new developments. In part 2: bug fixes on the released code I am suggesting a GitHub process, but it translates to other platforms with pull request support, E.g.: Azure DevOps, GitLab, Bitbucket, ... The examples are using the repository of the eLoad. I am using a single repository but it works virtually the same if contributors work from their own forked repository.     Branch Str ...
I'm trying out OBS as recording software. It allows to mix sources on a single screen. In my case: laptop camera for my face USB cam for the bench, taped to a chair 3 windows: DMM display, eLoad display and datasheet in acrobat reader record from Jabra wireless headset microphone.     There are some watchouts: resizing the windows can make characters too small for reading (see eLoad window) my layout is way too busy - less is more Better cam for the bench would be appropri ...
When you want to make an electronics video, you sometimes like to run your DMM Windows software on screen when showing what you do. Look at Louis Rossmann. He uses "Paul Daniels Software" to show his DMM measurements while probing Apple laptops. Because it is from Paul Daniels, it's perfect and will always show on top - he built that into the software.   Most of the Windows software that comes with my DMMs, oscilloscopes, ... don't have that option. But there's a Windows freeware that t ...
Jan Cumps

Reel to Reel deck

Posted by Jan Cumps Dec 2, 2015
I've purchased a 1977 vintage tape deck yesterday. It was a bit of a wild purchase, because I couldn't test it. It turns out that it's performing well. It's not a top model. 30Hz - 20kHz on low speed, 28 kHz on high speed.   Documentation is available from hifiengine.   Here's my first checkout:   ...

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