Tag: test

PC817 Optocoupler Tester – Lazy Sunday Afternoon Project

For some upcoming projects, I’ll use the PC817 optocoupler family. But sadly, you don’t always get what you think you’ve bought. So how can you simply check if they work as described in the datasheet? I wanted a quick way to verify parts before building them in.

This small tester consists of two independent circuits, runs on 5 V, and does two simple things:

  1. Quick Test – Push the switch, and if the LED lights, the optocoupler basically works.
OptoCoupler_CheckCircuit_QuickManual
  1. Frequency Test – Based on the circuit from the datasheet. Input impedance is 50 Ω, and the output can be pulled up with 100 Ω, 1 kΩ, or 10 kΩ to see how the device behaves at different frequencies.
OptoCoupler_CheckCircuit_ParameterCheck

Simple stripboard:

0002-PC817-Series-PhotoCoupler-Tester_SB

That’s it.
It’s not meant to be fancy—just a tiny 2-hour project to get reliable data and a feel for how different PC817 batches respond.
The project data will be on Gitea – ToGo-Lab, Project ID 0002,

As working proof, some simple scope screenshots:

If you’re into optocouplers or small test circuits, feel free to build along or suggest tweaks.
Always happy to hear what others find useful in their own setups. 🙂

Old meter (MXD-4660A), new tricks.

I pulled my veteran DMM, a Voltcraft MXD-4660A, from the drawer to set up my workbench (adding a serial-to-USB converter) and gave it a second tour of duty with QtDMM on Ubuntu. After a bit of searching online what to use under I found the QtDMM project at http://www.mtoussaint.de/qtdmm.htmlm , but appears abandoned. The active fork, I think, is at https://github.com/tuxmaster/QtDMM.

Here’s the final install and setup for my lab computer running Ubuntu 22.04 (Jammy):

Build & Install QtDMM on Ubuntu 22.04 (Jammy)

1) Prerequisites

  • Enable Universe and base tools:

    sudo apt update
sudo apt install -y software-properties-common
sudo add-apt-repository -y universe
sudo apt update

  • Compilers, build tools, VCS:

    sudo apt install -y git build-essential cmake ninja-build pkg-config

  • Qt6 SDK

    sudo apt install -y qt6-base-dev qt6-tools-dev qt6-tools-dev-tools qt6-l10n-tools libqt6serialport6-dev

  • HID API

    sudo apt install -y libhidapi-dev libhidapi-hidraw0

  • OpenGL headers for Qt6Gui/Widgets

    sudo apt install -y libopengl-dev libgl1-mesa-dev libglu1-mesa-dev mesa-common-dev

  • Serial access without sudo:

    sudo usermod -aG dialout "$USER"

  • Log out and back in to apply group membership

2) Get the source and make the script executable

git clone https://github.com/tuxmaster/QtDMM.git
cd QtDMM
chmod +x compile.sh

3) Build

  • Clean build (optional). Also verifies prerequisites are present. 
    ./compile.sh clean || true
rm -rf build CMakeCache.txt CMakeFiles
./compile.sh
  • Artifacts land in ./bin/: 
    ./bin/qtdmm --version
  • Verify it runs. If not, see Troubleshooting below

4) Install for all users (see §5 for a .deboption)

Preferred:

sudo ./compile.sh install
# now on PATH:
qtdmm --version

5) Alternative: make a .deb

Keeps your system clean and is easy to remove later.

./compile.sh pack
sudo apt install ./QtDMM_*amd64.deb

6) Uninstall

If installed via .deb:

sudo apt remove qtdmm

If installed via compile.sh install:

# run from the same build dir used for the install
sudo xargs rm < build/install_manifest.txt

Troubleshooting:

If you hit errors, try a clean build reset instead of first searching forums. I learned the hard way to make a clean install as a belt-and-suspenders reset, that deletes built objects but keeps the CMake cache.

  • “|| true” lets the sequence continue even if the clean step fails due to a broken config.
  • “rm -rf build CMakeCache.txt CMakeFiles” force-removes any stale out-of-source build dir and any accidental in-source CMake cache:
  • “Final ./compile.sh” does a fresh configure and build: 
cd ~/QtDMM
./compile.sh clean || true
rm -rf build CMakeCache.txt CMakeFiles
./compile.sh

Let’s check if it’s running

  • As your regular user, start QtDMM from the command line or via the Ubuntu Dock (search for “QtDMM”):
  • Hint: How to create a Desktop shortcut launcher for ubuntu 22.04
    QtDMM - Running

  • Configure settings for MXD-4660A:
    Setup Voltcraft MXD-4660A

    Final test setup (send a known signal) and the result: MXD getting some imput from generator to prove reading
    QtDMM running, getting Data


Question to readers: Is there Linux software for the old Hameg HM1507-3? I’m currently using a Windows XP VM with very old software.