JULY 2020 Meeting Report

Progsig 14 July 2020

Present: Steve, Alex, Anthony, Bob, David, Geoff

Listen only : Andrew, Martin

Alex

Update on his Power Supply Unit (PSU) showing noise measurements from a digital scope.

Without a filter noise on the DC output is around 300mVrms, with filter it is about 80mVrms.

This figure includes noise picked up by the scope probe from the environment.

See Analog Devices AN1144 for more details on PSU noise.

The most effective result came from using low ESR capacitors.

Two x 22uH inductors were specified in the filter but it was found that with only 1 inductor the result was basically the same.

Alex wound the inductors by hand - there's a colour code for ferrite cores to indicate permeability, but it is not industry

wide or standard.

There are some details here:

https://www.nutsvolts.com/questions-and-answers/permeability-measured

Alex also made some audio speakers that fit under his screen. After experimenting, he found that they sounded

better without any enclosure.

Link to 'open baffle' speakers :

https://hometheaterhifi.com/editorial/oped/are-open-baffle-speakers-a-flawed-technology/#:~:text=An%20open%20baffle%20speaker%20is%20a%20good%20example,back%20at%20the%20same%20time%20%28aka%2C%20same%20phase%29.

Steve

Phase 2 of dust management at Leichhardt Mens Shed is automated blast gates.

The blast gate is generally a sliding door mechanism (some pivot) connected in line with the suction hoses.

It enables unused gates to be closed so that the machine in use has the only open gate and therefore

gets maximum suction.

I played a video that showed an automotive central locking solenoid (Jaycar $13) pushing a mechanism

that moves the blast gate door open and closed.

It is a bit violent and might shake itself apart over time.

I wrote a quick arduino program to operate the device for 100 open/close cycles with 25secs in between. I've run this a few times and its still going. The control needs 2 relays - a power ON/OFF relay (SPDT) and a polarity reversal relay (DPDT).

Next I'll try with a servo motor which should be a slower action, if it is powerful enough.

PS 12V DC linear actuators cost about $60 and they are slower moving, so these alternatives are being investigated.

Anthony

Talked about the programming language Java script & Node the Javascript interpreter.

Node.js is the official name of Node and includes the libraries ie the ecosystem.

ECMAscript is the proper name for Javascript

Python is another more recent and widely used language, with 'a library for everything'.

Bob

Uses the vivaldi browser as an alternative to Google snooping on all your browsing.

From wikipaedia :

"Vivaldi is a freeware, cross-platform web browser developed by Vivaldi Technologies, a company founded by Opera Software co-founder and former CEO Jon Stephenson von Tetzchner and Tatsuki Tomita. It was officially launched on April 6, 2016.

Although intended for general users, it is first and foremost targeted towards technically-inclined users as well as former Opera users disgruntled by its transition from the Presto layout engine to a Chromium-based browser that resulted in the loss of many of its iconic features. Despite also being Chromium-based, Vivaldi aims to revive the features of the Presto-based Opera with its own proprietary modifications.

As of April 2020, Vivaldi has 1.5 million active monthly users.

Vivaldi released a mobile (Android) beta version on September 6, 2019 and a regular release on April 22, 2020.