Forum - Recent Threads

The PAM8403 amplifier is very noisy

me_Cris — Sat, 25 Apr 2026 15:37:31 GMT

Hi!

I was thinking of participating in a challenge but I ran into another challenge. 😅
I'm using a small circuit with PAM8403 as a replacement for some speakers with dead audio circuit. In addition, I also have addressable LEDs in the case (this how they came) and I was thinking of using an MCU to control them. But I just noticed a very sharp and annoying noise produced when I power the LEDs, and it doesn't go away even when playing music.
I made a msall PCB, the schematic is below. The power supply is at 5V [USB]. I placed some capacitors in the idea to support the supply voltage.
What ideas do you have? What could I improve?

Thanks!

The schematic:

The layout:

PAM8403 module:

The initial amplifier + controller board:

The speakers:

My assembly:

Keychron has released the CAD models for their mice and keyboards

stanto — Wed, 08 Apr 2026 23:50:08 GMT

Available here: https://github.com/Keychron/Keychron-Keyboards-Hardware-Design

All the industrial design files for Keychron keyboards and mice. Includes CAD models (case, plate, stabilizer, encoder, keycap) for Q, Q Pro, Q HE, K Pro, K Max, K HE, V Max, P HE series and M1–M7 mice. 100+ models. STEP/DXF/PDF formats. This project is source-available. Commercial use is strictly prohibited.

It looks like the github repo' has hit its download limit (I'm getting an LFS error when trying to clone). In case there's any problems grabbing it I've uploaded a snapshot here: Keychron Keyboards Hardware Design

They don't allow commercial use, win-win for us?

What's Inside

Series	Type	Models	Components
Q Series	Keyboard	Q0 Plus, Q1–Q12, Q60, Q65	Case, Plate, Encoder, Full Model, Stabilizer, OSA Keycap
Q Pro Series	Keyboard	Q1 Pro–Q14 Pro	Case, Plate, Encoder, Full Model, Stabilizer, KSA Keycap
Q HE Series	Hall Effect	Q1 HE, Q3 HE, Q5 HE, Q6 HE	Plate, Full Model
K Pro Series	Keyboard	K1 Pro–K17 Pro (16 models)	Case, Plate, Full Model, Stabilizer
K Max Series	Keyboard	K1 Max–K17 Max (11 models)	Case, Plate, Full Model, Stabilizer
K HE Series	Hall Effect	K2 HE–K10 HE	Case, Plate, Full Model, Stabilizer, Keycap (K2 HE; other models pending)
L Series	Keyboard	L1, L3	Case, Plate, Knob, Full Model, Stabilizer
V Max Series	Keyboard	V1 Max–V10 Max	Case, Plate, Encoder, Full Model, Stabilizer, OSA Keycap
P HE Series	Hall Effect	P1 HE	Case, Plate, Full Model, Stabilizer
Mouse Series	Mouse	M1–M7, G1, G2 (11 models)	Shell, Full Model

opa1633.lib ?

ronyd — Sun, 05 Apr 2026 20:35:50 GMT

Does anyone have the spice simulation model? TI for the opamp does not have the Tina-TI schematic file (.tsc suffix).

KiCad 10 is almost here

shabaz — Wed, 11 Mar 2026 15:53:15 GMT

KiCad 10 is about to be released soon (release candidate 2 is available), and I just recently checked out the new features list.. I'm surprised, that's a massive amount of features, and many of them look interesting.

Some of the features I can see myself using:

* Ability to implement jumpers properly

* Hatched fill - very useful for marking off areas of PCB on a silkscreen

* Something they call auto-route preview, which I believe just shows a possible routing completion for a single trace

* Dark mode for the application

* More graphical capabilities, such as scaling, and ability to precisely enter co-ordinate values for shapes

* PCB sub-circuits (I think)

For anyone not familiar with KiCad, but wishes to try it, I'm biased but still think one could do worse than viewing the 50-minute video I created a while back (ad-free, it's not monetised). The KiCad user interface has not significantly changed since the video was created.

A lot of beginner video tutorials initially avoid how to create custom symbols and custom footprints, but I included that in the 50 minutes, since it is key information needed for almost any project.

Creating Circuit Boards with KiCad

For other CAD software users, anyone tempted to give KiCad a tryout this year?

Also, there are other CAD version import capabilities, but personally I reckon that's not the best way to transition across, and is possibly more useful to users who are slightly familiar with KiCad, and then need to port across a few of their projects. Reason is, all PCB CAD systems implement some things differently, and you may want to tweak things after import, which is easier when you're at least slightly familiar with the new CAD package, by trying a few projects from scratch.

Man invents new type of compass - releases it to public domain for Christmas

stanto — Sun, 04 Jan 2026 01:45:27 GMT

www.youtube.com/watch

Even if you have no interest in compasses, the delivery of this video is fascinating to watch, and the details of the properties of metals applied to it make it all the more fascinating with a brief discussion in the pinned comment.

Not quite the kind of open source hardware you may be expecting.

Near ultrasound electromechanical cleaner with cd4011

madthescientist — Wed, 22 Oct 2025 11:42:51 GMT

I am trying to build an ultrasound or near ultrasound cleaning device using a CD4011 as pulse generator and two tip120, each one has the Base terminal connected to the outputs.

Whenever one turns on the other is off an vice versa.

However, i do have a problem: the man who gave me the circuit told me i do need two coils and strong magnets. He told me to do 200+200 turns with a common connector in the middle, aiming towards agitating a recipient full of cleaner.

I am feeding this circuit between 12v and 24v, the cd4011 itself has its own 7805 and coil in series regulator, to prevent power noise to get into the ic.

I have several problems to resolve and i do not know how:

I do need to find out the proper thinkness of the wire for the likely current and frequency,
I do need to find out the proper cores for the coils. Theoretically there should be a magnet in front of them which they would reject when energized, causing agitation in the recipient;

I have the idea of using a basculating plate held in the middle by bushings, some sort of silicon as centering spring and placing two coils below it and two small metal pieces to get the plate oscillating, all of that below water and the coils placed into a watertight container below, this whole system would work deep under cleaning solution. In that caise, should my idea be feasible, what kind of cores are better for frequencies between 15.000 and 20.000 oscillations per second? a friend of mine tells me i could use iron transformer cores but some others tells me i'd need a sort of iron and ferrite core.

Also, if i wish to make it more powerful replacing the tip120 by 2n3055 and enlarging the coils and cores into the next big size, what would turns, wire thickness and core material and size be?

MyGenWashy: From Vienna Hackathon to Open Source Smart Washing Machines — A Blueprint for Resilient Tech

mayermakes — Sat, 28 Jun 2025 11:34:36 GMT

It all started at Mariahilfer i, Vienna’s grassroots hub for resilient technologies, circular economy
projects, and hacking culture. During a hackathon hosted in this unique space—also home to the
Kintsugi Repair Café—Patrick Awart of IoT Austria kicked off an ambitious idea: Give old,
mechanically sound washing machines a second life by retrofitting them with open-source, smart
control electronics.

The project immediately resonated with Clemens Mayer—known to many in the Element14
Community simply as Clem. Clem is well known for his personal mission to ensure there’s at least
one reliable, open-source version of every essential technology, strengthening society’s resilience in
the face of closed ecosystems and throwaway culture. So naturally, he jumped on board.

Backed by Mayer Makes, IoT Austria, and the Mariahilfer i community, the MyGenWashy project
quickly evolved beyond a weekend hack—blending hardware hacking, Smart Home integration,
repair culture, and open-source compliance into one focused initiative.

community.element14.com/.../4604.Hackathon-EN_2D00_finial3.pdf

Smart Tech Meets Circular Economy

MyGenWashy retrofits old washing machines with generic control boards, designed to integrate
seamlessly into Smart Home systems via ESPHome and Home Assistant. Thanks to IoT Austria's
early ESPHome integration efforts, the machines can already be monitored and controlled over
local networks — with future interface options including reusing old smartphones as intuitive
displays and touch controls.
From a technical perspective, the team uncovered fascinating aspects of washing machine design
during teardown and reverse-engineering:

Air Pressure Water Level Control: A refreshingly simple mechanical system regulates
water levels—efficient and reliable.
Mechanical Safety First: Even generic control boards include hardware-based protections
against overflow and overheating.
Simplicity at Scale: Many washing machines, regardless of price point, share common
components like Darlington ULN2003 relay drivers.

The takeaway? The hardware is already durable. By replacing only the electronics with open, user-
serviceable, and Smart Home-compatible alternatives, we extend appliance life, cut electronic
waste, and empower users.

The Power of Community and Open Source Certification

This project isn't happening in isolation. Mariahilfer i also hosts the Kintsugi Repair Café, making
it the perfect hacking ground for repair-focused experimentation.
MyGenWashy ties directly into Smander.com's work on the Open Digital Product Pass (ODPP) —
an ambitious initiative to fulfill upcoming EU requirements for product transparency, circular
economy documentation, and CE-compliant, truly open-source hardware. In partnership withregulatory experts, ODPP aims to create verifiable, safe open-source designs that meet real-world
legal and technical standards.

Generous Hardware Support for a Repairable Future

The project wouldn’t have accelerated this fast without crucial support from hardware allies:

AISLER generously provided professional-quality PCBs for the prototype and development
phases, reinforcing their commitment to local, small-batch, repair-friendly production.

Farnell contributed essential components, helping Makers and engineers realize a fully
functional control board with energy-efficient, Smart Home-ready capabilities.

This shared mission—making hardware repairable, modifiable, and accessible—is at the heart of
the broader movement MyGenWashy embodies.

Once we get to a stage where Certification comes into play we can count on Smander.com to achieve this milestone.

Open Source, Fully Documented, Ready to Evolve

The complete MyGenWashy design, including schematics, component lists, and ESPHome
configurations, is available on GitHub for replication, modification, and iteration:
https://github.com/mayermakes/MyGenWashy
Beyond washing machines, the principles apply to other household devices—building a blueprint
for modular, repairable, connected hardware with community-driven innovation at its core.

Join the Mission: One Open Source Version of Everything

For Clem, Patrick Awart, Thomas Losert, and the wider community, this is more than a project—it’s
a movement toward resilient, sustainable technology.

Want to contribute to ODPP, open hardware standards, or MyGenWashy v2 and v3?
Interested in creating open-source, compliant alternatives to everyday tech?
Believe in empowering users to repair, reuse, and innovate?

The door is open:

contribute@odpp.at

http://odpp.at

Together, we can ensure the technology we rely on remains transparent, repairable, and open—
because resilient societies are built on resilient tools.

Open Hardware Summit 2025

stanto — Fri, 30 May 2025 22:44:28 GMT

Anyone in Edinburgh checked/checking it out?

I admit, I forgot, but I wanted to go D:

www.youtube.com/watch

Here's a list of the talks: https://2025.oshwa.org/talks/

Hah, the badge is textile, that's neat: https://www.hackster.io/00legendary/open-hardware-summit-badge-2025-941ee3

Bus Pirate v5: A RP2040-based troubleshooting/programming tool has been released, and it looks interesting

shabaz — Thu, 25 Jan 2024 17:26:05 GMT

I just saw this announced: a troubleshooting/development tool called Bus Pirate 5.

(image source: buspirate.com)

The hardware and firmware source are on GitHub.

In a nutshell, the Bus Pirate 5 is a command-line controlled (via its serial console) tool that can be used to send/receive a few typical board-level (and other) protocols, such as SPI and I2C, and also UART (and some protocols on top). It would be nice to see additional protocols, but there is plenty of space for that - It runs with an RP2040 chip (a very straightforward part to code for!), with 16 Mbytes of Flash - but there's also an additional 100MBytes on a Flash chip for storing (say) firmware images to upload onto hardware.

Interestingly, there is also a 1-5V supply on board with 500mA output capability, and this could be extremely handy.

What's also awesome is that the I/O (for eight pins) is configurable from 1.2V to 5V! That's extremely useful for the typical purposes of this board.

There is a plug-on LCD screen for monitoring purposes, plus (for reasons I don't understand yet, but perhaps it's handy for status and warning alerts, etc) there are also many RGB LEDs.

(image source: buspirate.com)

The price is extremely reasonable (although the cables for it add to the cost - but they could be DIY'd).

I hope someone eventually writes a Python interface for this (otherwise, I will do it myself). I hoped to use the BeagleConnect Freedom (BCF) for similar purposes, but they are useless at getting information out for people to develop with it; mine has been a (small) dead brick for half a year.

The Bus Pirate, on the other hand, is designed by Ian Lesnet. I purchased a couple of other boards originally designed by Ian (a logic analyzer and an FPGA board) a decade ago! They are excellent, so I've got high hopes for this board too.

Please ignore

shabaz — Fri, 24 Nov 2023 23:12:21 GMT

(Deleted, moving to Blog)

October is Open Hardware Month

cstanton — Wed, 14 Sep 2022 15:23:15 GMT

Cross-promoted from an e-mail I received:

https://ohm.oshwa.org/

https://ohm.oshwa.org/event-planning/

About OSHWA

The Open Source Hardware Association (OSHWA) aims to foster technological knowledge and encourage research that is accessible, collaborative and respects user freedom. OSHWA’s primary activities include hosting the annual Open Hardware Summit and maintaining the Open Source Hardware certification, which allows the community to quickly identify and represent hardware that complies with the community definition of open source hardware.

Get Involved

Label

Inspired by our Executive Director Alicia Gibb, and created by board member Jeffrey Yoo Warren, the Open Hardware Facts Generator helps you declare the licenses used in your project using a format similar to the US Nutrition Facts Label. Listing your licenses in one prominent place (such as the README of your repository) helps users immediately know what they can and can’t do with your source, rather than having to browse through individual files.

Certify

The OSHWA Certification continues to grow, with over 1,000 projects from over 40 countries! If you’re not yet familiar, the certification program provides a way for consumers to immediately recognize hardware whose meaning of “Open” conforms to the OSHW Definition. It also provides a directory for OSHW creators, which stands as evidence that your product is in compliance with the OSHW Definition.

Document

This is the time to document those projects you haven’t got around to yet, or update documentation that has been overlooked for a while. Documenting your hardware is the most important step in open sourcing your hardware because it gives other people a way to use, build upon, and possibly improve it. Publishing your design files publicly can also establish your hardware as prior art. If someone attempts to patent something similar, that prior art can prove that the hardware existed before the patent application, thus preventing it from being granted. Read about some best practices and show us your work @ohsummit!

Github

michaelkellett — Mon, 04 Jul 2022 08:48:20 GMT

After reading this consider if you still want to use Github.

https://techcrunch.com/2022/07/01/open-source-developers-urged-to-ditch-github-following-copilot-launch/?guccounter=1

I think I'll be closing my account.

HELP : Reviving RIoT Board a old Cool SBC

gsgill112 — Thu, 10 Feb 2022 15:04:41 GMT

Hi,

So, Like me many of us might have old SBC or powerful computers available at our disposal, but doe to the ever speeding pace of software development, often many of these kits die down due to lack of software support. An example is the RIoT Board, originally debuted around 2012-13 ( don't quote me on that) and post takeover of Freescale by NXP, died a peaceful death by around 2015-16. :( ;

let's keep silence for 1 min .......

Well now that's out of the way, So,

The board https://uk.farnell.com/freescale-riotboard/ , https://slowbootkernelhacks.blogspot.com/2017/01/riot-board-based-on-freescale-imx-6solo.html?m=0, https://community.nxp.com/t5/i-MX-Processors-Knowledge-Base/Task-2-First-build/ta-p/1112763, /products/devtools/single-board-computers/riotboard/#pifragment-3624=3, http://freescale.github.io/#

is not bad at all, I mean it is at par with Beagle Bone Black Rev C and Raspberry Pi 3 B, even better in some regards, in fact almost perfect for a NAS build using slow 5400 RPM 1TB 5V 0.6A HHDs and a cheep SATA to USB 2.0 adapter.

Obviously It's Not for the Speeds , but for the functionality.

It features,

NXP i.MX6Solo ARM Cortex-A9 processor @ 1Ghz
1Gbps Ethernet
1GByte of 32-bit wide DDR3 @ 800MHz
4GByte EMMC Flash, Full size SD and Micro SD card support
Supports Android and GNU/Linux
EMC Compliance - Class B certified
4 USB 2.0 Ports
Raspberry Pi Compatible headers
On board Serial port for debugging
On board JTAG interface
NXP Power Management Integrated Chip (PMIC MMPF0100) fully programmable, and unto 5V/ 3A Input power support
OpenGL® ES 2.0 3D graphics accelerator with a shader

So, Not at all shabby. It is a gigabit eth so Plex server + NAS. ?? :) that's a dream come true.

BUT, IT IS NOT SUPPORTED ANYMORE !!!!! and I could even speak to the Ubuntu repos of on board 11.10 builds. (But internet worked like a charm using old Firefox build on the board)

I tried the blogs already present and compiled 10 different roots, u-Boot and Linux kernel, etc and have just given UP. to update to a slightly recent linux version but to be true that is not my area of expertise.

So Need help of your brilliant minds to help me revive this kit and maybe give HOPE to old SBC's :)

side NOTE, could learn a ton of things :) especially the scary process of custom embedded linux builds.

Open Source options for RGB to HDMI

baldengineer — Mon, 16 Aug 2021 17:42:18 GMT

For my Mini Apple IIe project, I'd like to include HDMI output. This project is a one-off. So, I want HDMI to work, but I am not worried about passing compliance or licensing tests.

Ideally, I'd like to find an off-the-shelf chip that can take analog RGB signals, a sound input, and convert them to HDMI.

Why not DVI? The sound. From what I understand, DVI does not support a sound channel.

Looking around at the obvious semiconductor companies, it seems like analog-RGB to HDMI is something that exists. However, all require contact for more information. I suspect this step is to make sure you are licensed for HDMI IP. Fair step, but I am not selling anything.

On the grey market, I found the IT6613 (mirrored datasheet). It is used in the Open Source Scan Converter project. An interesting chip, it seems to do what I want, but it is huge and has a bunch of stuff I don't need.

I suppose one option is to do something with an FPGA. But I was really hoping to find something off-the-shelf.

I briefly looked at the Pi Pico PIO DVI implementation. But, again, the sound seems to be a stumbling point there.

Any ideas?

Are we finally at the point for open source, home made silicon?

cstanton — Sat, 14 Aug 2021 17:54:55 GMT

After discovering this tweet:

I clicked through to the video to discover this person's making their own silicon chips in their garage:

www.youtube.com/watch

Not everyone has this kind of home setup that this person has, however it may be the start of making hardware accessible to more than huge corporation manufacturing.

Eventually anyway. You can find more details at Sam Zeloof's blog.

Audio Transmission over BLE

aabhas — Mon, 31 May 2021 08:41:39 GMT

I am going to work on a project, and was wondering possible ways to transmit audio (captured from mic), to a android device or so over Wireless Bluetooth Low Energy (BLE), what could be best possible ways to explore to implement and do this, aim is to achive that with Arduino NANO 33 BLE Sense(given form factor and ease of dev), but am also trying to figure out on how it's done for other similar MCUs if not this, so it would be great if anyone has worked or knows could share about how can I start about achieving this goal of Audio Transmission over BLE...

Thanks

Aabhas Senapati

How to build a simple low cost reliable antenna switching circuit

BigG — Wed, 07 Apr 2021 13:37:43 GMT

I'm looking to build a simple (MVP: minimal viable product) BLE antenna array circuit to test BLE direction finding (AoA/AoD) functionality.

I'm not wanting precision just yet. So, for my MVP I'm looking at just 3 maybe 4 antennas. For that I will need an RF switch and if I look on any of the major distributor websites I can find plenty single pole 3 or 4 throw (SP3T/SP4T) options.

My question is how to build the input control side, which usually consists of logic table like this one (for a SP4T RF switch):

Input 1	Input 2	Output Mode
0	0	RF1 on
0	1	RF2 on
1	0	RF3 on
1	1	RF4 on

The switching frequency is at the microsecond(s) level.

My BLE chip is a single 3V3 MCU so I don't want to use this MCU to handle the switching as well as the other stuff. It's not a dual core PSoc, for example, where I could've used their hardware timer blocks etc.

So what IC options do I have with a power rail of 3V3.

Is it a case of using a precision Timer IC with some logic gates (e.g. OR, AND, NAND etc.) or would something like a tiny 8-bit MCU do the trick. Basically looking for as few components as possible which is low cost and reliable etc.

Looking to experts for some practical advice.

Thanks

Earth resistance meter FPGA

michaelkellett — Fri, 16 Oct 2020 09:20:38 GMT

It's been quiet on the ERM front - I posted my ideas for the main board design a couple of months ago and there has been very little comment.

I know that shabaz is doing some work and waiting for a display.

I had already decided that the power supply would be on its own board and I've blogged a bit about work done on that.

Part of the motivation in splitting it off was to ensure that the effort has some useful spin off for me, (it costs serious time and some money)

but also to generate designs that will attract enough interest to widen the support base beyond those who actually want an ERM.

With that in mind I've decided (probably) to do the same thing with the FPGA.

The original plan was to use a Lattice ICE40UP5K soldered to the main board.

I'm now considering fitting a 40 pin header to the main board so that the FPGA (on a separate board) can connect by direct plugging or by ribbon cable,

or a tangle of wires if necessary.

This will allow me to use a breakout board for a Gowin GW1N-9 FPGA, which is currently much more interesting to me than using the Lattice part.

It would also allow people to use pretty much any FPGA dev board so maybe all those people getting the free Arty boards might be interested in

a worthy target for their new skills.

I should get my Gowin breakout boards next week - they'll look like this:

The GW1N-9 has about 8k LUTs, 20 multipliers (18 x 18) in DSP blocks, 26 block rams (2k byte), SDRAM (8Mbytes) and on chip boot flash.

It's about the same price as the Lattice part (but harder to get) and can be obtained in an 88pin QFN.

The breakout board format I'm using is big enough to take a TQFP 144 pin package or a 256 pin BGA so Altera or Xilinx parts are possible.

It takes a single 5V supply and has on board regulators and oscillator.

I'll do an ERM compatible Lattice UP5K version of it too.

Comments , please.

ARMP Archaeology Resistivity Meter Project - base data

davemartin — Sat, 22 Aug 2020 09:03:38 GMT

Re the Archaeology Resistivity Meter Project (armp ), and further to the discussions on the injection aspect, and the linearity (or otherwise) of the ‘device under test’, I’ve run some tests. Main plots are included in-line below; fuller set available if needed. This first note is already rather long, so the next section with control plots and alternative stimuli etc. will follow in part 2.

ARMP – field plots, part 1

Purpose

Share data on characteristics of a typical archaeological earth resistance measurement path to assist with design of the Archaeological Resistance Meter Project (ARMP).

Test setup / conditions

Injection: +/5v from Wavetek 275; into HP 6826A bipolar amplifier (max +/- 50v, with constant-voltage and constant-current mode); injected current monitored via 100R 0.1% in series with amplifier output. Stimulation principally 137Hz square wave, plus selected other waveforms.

Monitoring: Fluke PM3394A (4 ch), waveforms captured single-sweep to capture peaks and also using in-scope averaging (32 sweeps) to give crude filtering.

Soil Probes: fixed (P1C1) and mobile (P2C2) probes, P1-C1 and P2-C2 0.5m separation, P1C1 and P2C2 up to 50m apart, leads (unscreened) in ‘twin-probe’ configuration as typically used in archaeological resistivity survey.

Target: marked 50m length of favourable but mixed ground (note a, b).

At each station along the test traverse, inject test 137Hz square-wave at 10 mA (note c), record injection waveforms C1C2 (voltage V1 and current I) and potential P1P2 (voltage V2). Main results in table 1.1 below.

Also - described in part 2 - record control plots (dummy load) and at selected stations P1P2 potential V2 with no injection to capture background electrical noise with, and without, 50Hz main electricity on in nearby property. At selected stations, in addition to 137Hz, also record with 32Hz and 80Hz square-wave stimulus, and with other non-square-wave stimuli (sine wave, triangle/sawtooth, trapezoid). Analysis of various stimuli to follow further in part 3.

Results

Injection

At intervals along the 50m traverse, the injection voltage (V1) necessary to inject the target current (I) was captured, below is a plot of V1 against distance (X) for each target current. Target I was nominal 10 mA, which required V1 in range +/- 30 to 45v; note that at 30 metre point where the test traverse encounters more stony terrain, the test struggled to inject more than 5 mA at +/- 55v.

Fig 1.1 – Absolute injected current (I) and necessary voltage (V1) vs distance (X) along test traverse

The injection waveform was also captured (V1 and I vs time T), below (figs 1.2, 1.3) are typical plots for target 10 mA at 15 metres. Injection waveform plots for each station, and reference plots, are available (note d)

Fig 1.2 – Injected current (I) and necessary voltage (V1) waveform at X=15m – single sweep

Fig 1.3 – Injected current (I) and necessary voltage (V1) waveform at X=15m – averaged in-scope

The upper (green) trace in figs 1.2 & 1.3 is the injection voltage V1. The lower (purple) trace is the current injected I. In this example (at X = 15m), V1 is +/- 35.1v and I is +/- 9.5 mA (measured as +/- 0.95v across 100R).

P1P2 voltage

The differential voltage V2 between P1P2 was also recorded (no differential probe to hand so acquired by using one scope channel for P1 and one for P2, and subtracting ch2 from ch1). Figure1.6 below shows differential V2 at each station along the traverse, along with the injection parameters.

Fig 1.4 – Absolute injected current (I) and voltage (V1), and differential P1P2 (V2)
vs distance (X) along test traverse

Fig 1.5 – Injected current (I) and voltage (V1) and differential P1P2 (V2) waveform at X=15m – single sweep
Upper (green) trace is the injection voltage V1; central (purple) trace is the current injected I;
lower (blue) trace is differential P1P2 (V2)

Fig 1.6 – Injected current (I) and voltage (V1) and differential P1P2 (V2) waveform at X=15m – averaged in-scope

The effects of the injection waveform will discussed more in part 2.

Resistance

At each test station, waveform was captured with potential P1P2 (V2) and injected current C1C2 (I) against time, and resultant apparent resistance (R2) derived. Sample below at 15m station.

Fig 1.7 – Injected current (I), differential P1P2 (V2), and derived soil resistance (R2) waveform at X=15m

Values for R2 at each test station against distance X are:

Fig 1.8 – Soil resistance R2 (V2/I) vs distance (X) along test traverse

And, just for reference, the same plot but including with values for R1, the resistance encountered by the injection circuit, which shows the effect of contact resistance:

Fig 1.9 – Soil resistance R2 (V2/I) and injection resistance R1 (V1/I) vs distance (X) along test traverse

Key data

Table 1.1 – Key measurements obtained with 137Hz square-wave excitation
V1/I/R1 injection C1C2; V2/R2 soil sample based on P1P2 potential and injected I
P1C1 static at 0 metres; P2C2 moved to each station in turn
(voltages and current are +/- value shown)

Comments

The ‘inrush’ when injection is applied can be seen in the injection (V1, I) vs time plots (figs 1.2, 1.3), the differential potential plots (figs 1.,5, 1.6) and the derived resistance plot (fig 1.7).
Even in relatively conductive soil conditions, when a small stony patch was encountered, +/- 50v injection was unable to inject 10 mA (fig 1.1, note e)
Spikes or ringing in V2 (P1P2) occur at the leading edge of each reversal, significantly in excess of the proportions exhibited by the injection waveform (see part 2).

Notes

(a) Test location – 50m traverse, no edge effects, damp soil. Slight 50 Hz mains, plus electric fencing energiser effect, plus other stray / telluric current; background noise plots taken P1P2 at selected locations with no injection with, and without, mains on in nearby property (see part 2).

(b) Earth path distance - in the main ARMP use case (twin-probe grid-survey) with 0.5m probe separation and 20x10m grids, the shortest earth path P1C1 – P2C2 would be 15m and the max usually 50m; but in use case 2 (Wenner x, Schlumberger etc.) and use case 3 (profiling) the P1C1 – P2C2 distance can be down to a metre or less, so results captured from 1 to 50 metres. Stations at 1, 2, 3, 4, 5, 7, 10, 15, 20, 25, 30, 35, 40, 45, 50m.

(c) ‘Constant’ current – the HP 6826A amplifier, when in constant current mode, was not able to hold constant-current at single-figure mA. Therefore, to constrain the variables, the amplifier was operated in constant-voltage mode with the current manually adjusted to average the target current for each test location; so at each location the current was a nominal metered 10 mA, but, as can be seen from the plots, there was variation during the duration of each pulse due to the ‘inrush’ and polarisation; the derived resistance plots take account of this by using the measured rather than target current. At the 30m point, the ground was stony and the test struggled to inject more than 5 mA at +/- 55v.

(d) Injection performance – plots in part 2 include a control for each excitation using a fixed 4k7 resistor rather than the earth, to show amplifier performance, and effect of any mains ripple etc.

(e) Voltage limit – when the HP 6826A maxed-out at +/- 55v when trying to inject 10 mA at 30 metre location (shallow stony patch), a one-off trial attempt was made to continue using another higher-voltage constant-current source (Glassman LP100-12 constant-voltage and constant-current power supply) with external output reversal. 10 mA was eventually injected, but it took +/- 97v. The Glassman power supply (not an amplifier) takes up to 3-4 ms to stabilise after a load removal, so the reversal rate had to be slowed down (32 Hz was used).

Continued in part 2

DM 21 Aug 2020

Attachments:

community.element14.com/.../ARMP-plots-1-v07.pdf

ARMP plots 1 v07.pdf

Archaeology Resistivity Meter

kltm — Sat, 20 Jun 2020 08:47:23 GMT

Hi I'm looking for ideas on an update to a resistivity meter for archaeology. The only published designs for diy were in 2 magazines. One was published in 1997 and the other in 2003. I have copies of both articles available. The reason behind this is the current high cost of available equipment, usually well beyond the reach of most archaeological groups. I've attached a basic block diagram. In the first magazine article the meter is very basic. It relied on the operators to write down the reading given as the survey was taken. Given that a normal survey grid is 20m x 20m and 1 reading is taken on every sq mtr there would be 400 readings to write down and then input into a program used to interpret the results. The later article is really an update to the first where a PIC has been added to record the readings. This again is prone to error, because eadings are taken manually by pressing a button.

I'm sure given the advances in electronics there must be better ways.

CNC Interface Board discussion

shabaz — Sat, 10 Aug 2019 13:39:48 GMT

This is a thread to discuss ideas for controlling low-cost hardware (machines), for the purposes of cutting or engraving for example. It was created due to the interest in ralphjy project to assemble such a device.

There are several ways to do this, typically the 'brains' are a normal desktop or laptop PC, or a single board computer (SBC), and then there is some interface board, that then ultimately connects via high-power drivers, to the motors. There are some other bits of functionality too, like feedback (e.g. limit switches) for detecting end stops.

In terms of motors, in industry servomotors will be used, but for home use stepper motors are a lot more popular due to lower cost. For controlling the tool, a 'spindle motor' may be a brushless motor, or alternatively a brushed permanent magnet DC motor (i.e. BLDC or PMDC motor respectively).

The PC connection to the interface board can typically be a parallel interface, or USB. When using a SBC then its on-board general-purpose input/output (GPIO) can be used.

The BeagleBone Black (BBB) is worth considering I think, since it has been the first popular Linux product to be integrated into machines, providing functionality for 3D printers and small CNC machines. Commercial manufacturing products have been launched with the BeagleBone inside, such as the PocketCNC. There are also third party add-on boards that act as interface boards (and some that integrate motor drivers too). The BBB is old now, but there is a BeagleBone-AI that could in future be used as an upgrade.

Partly the reason the BBB has been useful is because it contains some programmable real-time units (PRU) internally, and they can override some GPIO pins, for direct control without needing to go through the Linux system. So, the Linux system can push code to execute on the PRU, and the PRU will control the pins. This means high speeds, and no unexpected delays or jitter, since the PRUs are simpler devices that do not run an operating system that could have a task preempted.

To control the interface cards, PCs have a wider choice of software, and popular choices are Mach 3 and LinuxCNC. For the BBB, the software all the boards seem to use is called Machinekit, which is a fork of LinuxCNC.

Using it for BBB is not documented well unfortunately. When I first started looking a while back, it was hard to tell which information works, and which information is old. I wanted to automate a simple XY table I'd bought.

However, there is a fairly recent blog article with useful pointers. It too discusses that information is spread out.

It would be nice to develop hardware (or to at least consider it first), and any software or configurations, documented, that would allow low-cost control of machines, and to bound it a little, to only consider home-grade machines using stepper motors, not servomotors. I think there is value in a new open source design, to collect up the wisdom of the various CNC users here, so we can all have low-cost home robots to make things for us!

After some initial thinking, these sketches were a couple of ideas: They are based around the thought that the BBB could be a plug-on daughter card on a larger interface board, that uses something like RJ45-style connectors (because it would be nice to use off-the-shelf cables where possible, to reduce wiring effort, otherwise there are a lot of wires to connect).

After some further discussions with balearicdynamics, it was suggested that scenario 1 could be more practical since it can handle more motors (low power and high power). I too like that idea, since it is one less board to make.

Edge connectors or some other connection location could still be left on the board, for those who do want to have a custom board for add-ons (e.g. to control a 3D printer instead, where they may need outputs for say a heater).

More input to any of this, including the practicality of it all, and board design (physical as well as functionality), and connector choices, is welcome. Meanwhile, I've been looking at the existing boards that are supported by Machinekit, to see what pins they use of the BBB, and why. I'll have to install Machinekit to better understand it. So far, I've looked at boards (or Machinekit configs) called CRAMPS, Replicape, and BeBoPr-Bridge and all use different pin mappings. I need to figure out which of these configs are using the PRU, and if so, which pins to allocate for that. I like the CRAMPS pin mapping so far, because it avoids eMMC and HDMI clashes (the BBB has these brought out to its connectors, and some interface boards tend to use these, which rules out using eMMC or HDMI as a result).

The pin mappings are in text files, but not easy to compare, so I've put them in a spreadsheet, I'll attach that as soon as it is complete.

The pin mapping text files are: CRAMPS.hal, replicape.hal, BeBoPr-Bridge.hal (I'll look at a few more too, and put them in the spreadsheet).

The mappings are numbers like 817, which means header P8 on the BBB, pin number 17.

EDIT: I'd hoped to daisy-chain the supplies, but looking at the user docs of a random one, it recommends against this practice:

So, the in/out connectors may not be a good idea, and a single power connector on each motor driver could be preferred.

I'm still looking for a suitable connector, but thinking it may as well be another RJ45-style, since I cannot think of another high power cheap alternative. Ethernet will carry lots of current safely, if wires are paralleled. There is the risk of accidentally plugging it into the wrong socket, but they could be color coded.

Zephyr OS 1.14 (LTS) Bug Fixing Contest

kjachim — Wed, 27 Mar 2019 18:44:39 GMT

Calling all Zephyr contributors! As the Zephyr Project community prepares for the release of ZephyrOS 1.14, they are rewarding the top 5 contributors with the most bugs fixed in Zephyr OS 1.14 with an NXP i.MX RT1050 EVK! Learn more about the contest here:

https://www.zephyrproject.org/zephyr-os-1-14-lts-bug-fixing-contest/

An Open Source Tablet with many compatibilities

diskiopi — Wed, 07 Nov 2018 15:44:42 GMT

Hello E14 community,

I'm Guillaume from Diskio Pi.

I would like to introduce you my product, an Open Source Tablet for all your touch screens projects.

Diskio Pi is compatible Raspberry Pi (all models, except compute module), Odroid C1+/C2, and more, like UP board, Pine64 ...

13'3 HD screen, capacitive touch, internal usb hub, 5v@4A power, sound, etc.

Some options will be also available, like VESA support, cooling solution, SSD 2'5..

If you're intersted by this project, you can have a look on the crowfunding campain: https://www.kickstarter.com/projects/diskiopi/diskio-pi-the-ultime-open-source-tablet-0?ref=arby52

Some early birds offers are still available.

Thank you !

Guillaume

How usually long is the back order for MSP-EXP430FR6989?

composi — Sun, 01 Jul 2018 09:13:35 GMT

I ordered a MSP-EXP430FR6989MSP-EXP430FR6989 at Jun 20th and the site says there are some parts that are available for next business day delivery But now it's been two weeks but there's still no news about it

Pentium 5005 and DDR4 footprints for electronic development

madscientist1500 — Sun, 08 Apr 2018 19:49:06 GMT

Hello everyone.

I am willing to develop a single board computer using an Intel Pentium Silver 5005 SOC and adding DDR4 slots for RAM.

I would likely be using software like altium or kicad, that's the reason i wou like to ask if is there any manner of getting

the proper footprints for this chipset and memory so i can start building up a library of parts.

Thanks fr yoour help.