Sunday Meetup - 29th January at the Welshmill Hub

It’s nearly time for our regular last-Sunday-of-the-month afternoon session! Do join us. We’re meeting from 14:00 til 18:00 on Sunday 29th at the Remakery/Welshmill hub.

This is the first meetup of 2023 - it will be good to see everyone who can make it, after the year-end break.

Feel free to bring any projects you’re working on, use the tools, discuss any interesting tech you’ve been looking into, ask questions, or just catch up.

The 3D printer is ready for action, as is the laser cutter, and also the CNC machine (but that needs a training session and a bit of supervision to use.)

When: 2pm - 6pm Sunday 29th January.

Who: members and prospective members.

Where: The Remakery, upstairs at Welshmill Hub, Park Hill Drive, BA11 2LE . (Park Hill Drive is off Welshmill road, near the Play Park/Bump Track)

We had a good session yesterday, although with a relatively low attendance.

@Joe did some regular maintenance, @Al_B did some research on user-friendly affordable website authoring, @Will did some endless updating of software on his laptop.

@hugo ran a 3D print job on the Make:Shed’s Prusa, a coil-former for an idea he has involving magnetic sensing. Watch this space.

Hugo also brought a couple of his projects, both musical instruments using lasers, light detectors and a small affordable microcontroller board based on the ESP32. (He’s doing his programming in the Arduino world, which would suit various microcontrollers. This one has lots of analogue inputs and also Bluetooth, and the processing power he needs to synthesise audio.) Here’s a detail of the laser harp (it’s battery powered, uses a green laser pointer, has 9 pairs of light sensors and 9 clear plastic beam-splitters.)

And here’s his other musical project, a prototype laser Theremin, again powered by ESP32, this time with a 3D-printed former to hold the laser diode and three light sensors:

Of course we played a bit with the laser harp! We also had a wide-ranging conversation covering time travel, science fiction, the latest AI chat bots, various perils and opportunities of modern technology, and more besides.

The 3D print finished exactly on the closing bell at 6pm, due to a carefully calibrated 116% print speed.

Oh, and Hugo also shared some samples of blue-green and green algae for us to conduct breeding or solar power experiments. See this other topic:
Algae batteries

Thanks for the writeup of the laser harp and other items.
I have wound the coils on the 3D printed coil former. The intention is to use it to detect the proximity and position of a metal object. i,e. how far away it is and its horizontal position, To then calculate X and Z position.
One transmit coil and 3 receive coils.
Using the pulse induction technique: the TX coil is pulsed, which induces an eddy current into the metal object, which thus produces an alternating magnetic field, picked up by the receive coils.
I have added capacitors across the coils, the LC circuits resonate at 13 kHz,
I need to sample the signal at preferably 10 times this, and for 4 channels. (3 RX channels, and also the TX signal) 130 KSPS x 4 = 520 KSPS. Not sure that the ESP32 is up to the task though…

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I found some example code for the ESP32 for ADC using DMA. And loaded it into the ESP32. A comment in the code indicates it working at 277 KSPS. Not sure I believe it though, as there seem to be successive samples with identical values. I reduced the rate to 200 KSPS, and the problem improved. But this sample rate is far from what is needed. So I have ordered an inexpensive board based on the STM32F401: 🇬🇧 STM32F401 84MHZ 256K Black Pill STM32 ARM Board better than Blue STM32F103 | eBay
The STM32 has a sequencer that selects in turn the ADC channels, and stores them into an array. The ADC operates up to 2.4 MSPS.

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As an aside, I have tried an ESP32-S2 board. Really compact and inexpensive. However, it is a real pain to use with the Arduino IDE. It loses communication via USB after programming, so that it is then not possible to read data into the IDE terminal, or plot graphs. Reset attempts then randomly change the com port number! Which then requires more faff to re-establish communication. I don’t have this problem with the ESP32 used for the laser harp. That is a WEMOS LOLIN32 ESP32 Lite

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