Line of electromechanical water valves dispensing a pattern of water droplets

Gravity-Defying Water Drop Display Shows Potential

October 23, 2021 by Dave Rowntree 9 Comments

[3DPrintedLife aka Andrew DeGonge] saw that advert for gatorade that shows some slick stop-motion animation using a so-called ‘liquid printer’ and wondered how they built the machine and got it to work so well. The answer, it would seem, involves a lot of hard work and experimentation.

Conceptually it’s not hard to grasp. A water reservoir sits at the top, which gravity-feeds into a a series of electromechanical valves below, which feed into nozzles. From there, the timing of the valve and water pressure dictate the droplet size. The droplets fall under the influence of gravity, to be collected at the bottom. From that point it’s a ‘simple’ matter of timing droplets with respect to a lighting strobe or camera shutter and hey-presto! instant animation.

As will become evident from the video, it’s just not as easy as that. After an initial wobble when [Andrew] realised that cheap “air-only” solenoids actually are for air-only when they rusted up, he took a slight detour to design and 3D print his own valve body. Using a resin printer to produce fine detailed prints, enabled the production of small internal passages including an ‘air spring’ which is just a small chamber of air. After a lot of testing, proved to be a step in the right direction. Whether this could have been achieved with an FDM printer, is open to speculation, but we suspect the superior fine detail capabilities of modern resin printers are a big help here.

In a nice twist, [Andrew] ripped open and dissolved a fluorescent marker pen, and used that in place of plain water, so when illuminated with suitably triggered UV LED strips, discernable animation was achieved, with an eerie green glow which we think looks pretty neat. All he needs to do now is upgrade the hardware to make a 3D array with more resolution, and he can start approaching the capability of the thing that inspired him. Work on some custom electronics to drive it has started, so this is one to watch in the coming months!

We’ve seen many water-based display device before, like this one that projects directly onto a thin stream of water, and this strangely satisfying hack using paraffin and water, but a full 3D Open Source display device seems elusive so far.

All project details can be found on the associated GitHub.

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New Part Day: Raspberry Pi LEGO HAT

October 21, 2021 by Dave Rowntree 18 Comments

The Raspberry Pi Foundation have been busy little bees for the last couple of years producing their own silicon, new boards and now in collaboration with the LEGO Education team a new HAT to connect to the LEGO SPIKE education platform. This new HAT board will work with every Raspberry Pi board with a 40-pin GPIO header.

Based on the RPI2040 microcontroller, it makes an interesting detour away from dumb slave boards, although it looks like the firmware is closed (for now) so you’ll have to make do with the pre-baked capabilities and talk to it with the supplied python library.

According to the documentation, the communication between the Pi and the RPI2040 nestled beneath the HAT PCB is plaintext-over-serial, freeing up the majority of the GPIO pins for other uses. The board uses a surface mount pass-through type header which allows pins from the Pi to protrude through the PCB, allowing stacking more HATs on top. Curiously they decided to mount the PCB with active parts facing down, giving a flat rear surface to park things on. We suspect that decision was made to improve access to the LPF2 connectors, especially if they were surface mount parts.

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3D Printable Scope Probe Adapts To Your Needs

October 21, 2021 by Dave Rowntree 18 Comments

If there’s one this we electronics engineers are precious about, it’s our test gear. The instruments themselves can be obscenely expensive, since all that R&D effort needs to be paid back over a much smaller user base compared to say a DVD player. The test probes themselves can often come with an eye-watering price tag as well. Take the oscilloscope probe, pretty much everyone who tinkers with hardware will be familiar with. It’s great for poking around, looking desperately for inspiration when you’re getting stuck in with some debug, but you’ve only got two hands, and that doesn’t leave any spare for button pushing.

Hands-free probing solutions exist, but they can be pricey, flimsy or just a pain to use. Sometimes you just want to solder a wire and leave the probe attached, hoping the grounding lead doesn’t fall off and short something. We’ve seen many solutions to this, so here’s yet another one you can 3D print yourself, so it’s almost free to make.

The two-part 3D printed assembly embeds a pair of wires with a Molex 0008500113 sprung terminal on one end, which can be terminated with your choice of pins, headers or just a pair of plain ‘ol wires. Once you’ve dropped your wiring of choice inside, simply glue the halves with a little cyanoacrylate and you’re good to go. Designed around the Siglent 200MHz PP215 specifically, it is likely compatible with many other brands. Thingiverse only has STL files (sigh!) so it may be tricky to adapt it to your exact probe dimensions, but the idea is good at least.

There is no shortage of electronics probing solutions out there, and boy have we covered a few over the years, here’s a low-cost current probe, an Open Source 2 GHz scope probe, and if you want to get really hacky, look no further for inspiration than the 2019 Hackaday SuperCon SMD Challenge.

Thanks [daniel] for the tip!

Quit Hunching Over Your Screen With A Little Robotic Help

October 20, 2021 by Dave Rowntree 8 Comments

[Norbert Zare] has identified a problem many of us suffer from – chronically bad posture. Its very common to see computer users hunched forwards over a screen, which eventually will lead to back problems. He mentions that most posture correction devices are pretty boring, so the obvious solution to [Norbert] was to build a simple robot to give you a friendly nudge into the correct position.

This simple Arduino-based build uses the ubiquitous MPU-6050 which provides 3-axis acceleration and 3-axis gyro data all processed on-chip, so it can measure where you’re going, which way you are orientated and how fast you are rotating. This is communicated via the I²C bus, so hooking into an Arduino or Raspberry Pi is a simple affair. There are plenty of Open Source libraries to work with this very common device, which helps reduce the learning curve for those unfamiliar with programming a fairly complex device.

At the moment, he is mounting the sensor on his body, and hard-wiring it, so there’s already some scope for improvement there. The operating premise is simple, if the body angle is more than 55 degrees off vertical, move the servos and shove the body back in to the correct position.

The project GitHub has the code needed, and the project page over on Hackaday.io shows the wiring diagram.

We have seen quite a few projects on this subject over the years, like this one that sends you mobile notifications, an ultrasonic rangefinder-based device, and one that even uses a webcam to keep an eye on you. This one has the silliness-factor, and we like that round these parts. Keep an eye on [Norbert] we’re sure there more good stuff to come!

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The Quadrivium EnsembleBot Is A Labour Of Love

October 19, 2021 by Dave Rowntree 5 Comments

The Quadrivium EnsembleBot project is a mashup between old school musical instruments and the modern MIDI controlled world. Built by a small team over several years, these hand crafted instruments look and sound really nice.

The electronics side of things is taken care of with a pile of Arduinos and off-the-shelf modules, but that doesn’t mean the design isn’t well thought through, if a little more complicated than it could be in places. Control is taken care of with a PC sending commands over the USB to an Arduino 2560. This first Arduino is referred to as the Master Controller and has the immediate job of driving the percussive instruments as well as other instruments that are struck with simple solenoids. All these inductive loads are switched via opto-isolators to keep any noise generated by switching away from the microcontroller. A chain of four sixteen-channel GPIO expander modules are hung off the I²C bus to give even more opto-isolated outputs, as even the Arduino 2560 doesn’t quite have enough GPIO pins available. The are a number of instruments that have more complex control requirements, and these are connected to dedicated slave Arduinos via an SPI-to-CAN module. These are in various states of development, which we’ll be keeping our beady eyes on.

One of the more complex instruments is the PipeDream61 which is their second attempt to build a robotic pipe organ. This is powered by a Teensy, as they considered the Arduino to be a little too tight on resources. This organ has a temperature controller using an ATTiny85, in order to further relieve the main controller of such a burden and simplify the development a little.

Another interesting instrument is Robro, which is a robotic resophonic guitar which as they say is still work in progress despite how long they have been trying to get it to work. There’s clearly a fair bit of control complexity here, which is why it is taking so much fiddling (heh!) to get it work.

This project is by no means unique, lately we’ve covered controlling a church organ with MIDI, as well as a neat Arduino Orchestra, but the EnsembleBot is just so much more.

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It’s A Hack: Air Scrubber Controlled Using The Room Lighting

October 16, 2021 by Dave Rowntree 8 Comments

Some products just seem to be designed to be annoying. [hardmar] discovered the air filtration system installed in his son’s basement woodshop was orientated for the best airflow, but rather poorly positioned to actually turning the thing on and off. For some reason the unit has its single line-of-sight IR receiver on one side, which when mounted in some positions, forces the user to be the completely wrong position to use the supplied remote.

We find it a little unhelpful sometimes that devices specifically designed to be mounted with varying orientations don’t come fitted with IR receivers in different locations to ensure good controllability. It would get annoying really fast to have to contort oneself into some specific position just to turn something on, and some people just might not bother at all.

Proper control of dust is paramount for continued good health, and essential in any workspace or shared area. When you work wood, it produces a lot of dust. It cannot be avoided and gets into everything, your lungs included. PPE is not enough. Even in your own shop you still really should manage dust production as best you can. Options are varied from centralised extraction, per machine solutions, and often augmented with air scrubbers mounted on the ceiling to grab those fine particulates.

Instead of solving the IR placement issue, [hardmar] wanted to have the unit tied to the lighting system so that it would power on as soon as someone turned on the appropriate light and would then stay on for a fixed amount of time after the user left in order to continue scrubbing the air some more. His simple hack was to first record and analyse the IR protocol used by the remote, and program an Arduino to be able to send it on/off commands. Next, he hooked up a phototransistor aimed at the light, in order to provide the necessary ‘user present’ trigger to tell the Arduino when to activate the scrubber. Super simple and effective. We love this non-invasive approach of adapting off-the-shelf equipment to our specific requirements, without even showing it a screwdriver.

As [hardmar] admits, the hack is not elegantly implemented, it’s just enough to make it work, and that’s just fine, sometimes you just have a job to do and no more.

PCB sitting inside a 3D printed holder job, with holes to apply vacuum

Solder Paste Stencilling That Doesn’t Suck

October 13, 2021 by Dave Rowntree 7 Comments

Working with solder paste stencils can be a real faff, they rarely sit flat and move around when you so much as breath on them. [Unexpected Maker] airs his frustrations, and comes up with a simple solution, he simply makes a 3D-printed jig to align the PCB panel and applies his shop vacuum cleaner and hey presto!

If you’re ever been tempted to switch from frameless to framed solder stencils, then you’ll notice they can be rather awkward to work with. The usual online vendors have plenty of listings for stencil frame holders, but they do all seem to us, exactly the same, and more suited to stencilling T-shirts, than working with tiny PCB footprints.

The problem with unframed stencils is one of clamping and registration to the PCB, which framed stencils fix, when used with a jig that can dial in the rotation and translation errors.

But problem with those is, unless you have a perfectly flat support region all round the PCB, the weight of the frame tends to make the stencil bow up over the PCB, causing parts of it to lift away from the solder lands. This results in paste not being pushed into the places you want it, and instead it sticks to the stencil apertures and comes away when you lift it up. Most irritating.

You can try offset it by taping spare PCBs of the same thickness all around, but this is not always terribly successful in this scribe’s extensive experience doing this job by hand. [Unexpected Maker] solves this bowing issue by making a 3D printed jig that bolts to the stencil holder, takes a custom top plate with holes in, which in turns allows a vacuum to be applied from below. This sucks the PCB down to the jig, keeping it flat (in case it is also warped) and also pulls the stencil plate directly down to the PCB, making it also lie perfectly flat.

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