Useless Machine For An Existential Quandary

There’s no project that dives into existential quandaries more than a useless machine, as they can truly illustrate the futility of existence by turning themselves off once they have been powered on. Typically this is done with a simple switch, but for something that can truly put the lights out, and then re-illuminate them, [James]’s latest project is a useless machine that performs this exercise with a candle.

The project consists of two arms mounted on a set of gears. One arm has a lighter on it, and the other has a snuffer mounted to a servo motor. As the gears rotate, the lighter gets closer to the candle wick and lights it, then the entire assembly rotates back so the snuffer can extinguish the flame. Everything is built around an Arduino Nano, a motor driver powering a Pitman gear motor, and a set of Hall effect sensors which provide position data back to the microcontroller.

If you’re in the mood for a little existential angst in your own home, [James] has made the project files available on his GitHub page. We always appreciate a useless machine around here, especially a unique design like this one, and one which could easily make one recognize the futility of lighting a candle at all.

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A Hoverboard As An Assistive Device

Assistive devices for people with disabilities can make an inestimable difference to their lives, but with a combination of technology, complexity, and often one-off builds for individual needs, they can be eye-wateringly expensive. When the recipient is a young person who may grow out of more than one device as they mature, this cost can be prohibitive. Some way to cut down on the expense is called for, and [Phil Malone] has identified the readily available hoverboard as a possible source of motive power for devices that need it.

Aside from being a children’s toy, hoverboards have been well and truly hacked; we’ve featured them in Hacky Racers, and as hacker camp transport. But this is an application which demands controllability and finesse not needed when careering round a dusty field. He’s taken that work and built upon it to produce a firmware that he calls HUGS, designed to make the hoverboard motors precisely controllable. It’s a departure from the norm in hoverboard hacking, but perhaps it can open up new vistas in the use of these versatile components.

There is much our community can do when it comes to improving access to assistive technologies, and we hope that this project can be one of the success stories. We would however caution every reader to avoid falling into the engineer savior trap.

An EV Motor Controller Home Build

Many of us will have experimented with brushless motors, and some of us will have built our own controllers rather than using an off-the-shelf part. Doing so is a good way to understand their operation, and thus to design better brushless motor powered projects. Few of us will have gone as far as [etischer] though, and embarked upon building our own controller for a 300V 90kW traction motor.

The tricky part of a high power brushless motor controller lies not in the drive but in the high-power switching arrangements. He’s using a bank of IGBTs, and to drive them he’s using a smaller industrial variable frequency drive controller with its own output transistors removed. He takes us through some of the development of the system, including showing him blowing up a set of IGBTs through having too much inductance between transistors and reservoir capacitor, and then to his final design.

This is part of a project VW first converted ten years ago, and as part of a series of videos he’s produced one going through the whole project. It’s a fascinating breakdown of the parts required for an EV conversion, and the teething troubles he’s encountered along the way.

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FET Based Motor Driver Is Better Than L298N

If you want to build a small robot with a motor, you are likely to reach for an L298N to interface your microcontroller to the motor, probably in an H-bridge configuration. [Dronebot] has used L298N chips like this many times. In the video below, he uses a TB6612FNG instead, taking advantage of the device’s use of MOSFETs. The TB6612 may be a little more expensive, but it’s clearly worth it.

You can get breakout boards for the tiny chips. [DroneBot] looks at several ready-to-go breakout boards. They are not drop-in compatible, though. For example, the L298N can operate motors from 4.5 to 46V while the TB6612 can go from 2.5 to 13.5V on the motor voltage. The L298N also handles more current. However, because of its relatively low efficiency, it needs a heat sink. The TB6612 boasts up to 95% efficiency and also has a low current standby mode. Of course, the TB6612 drops much less voltage which is great if you are using low voltage motor.

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Spinning ESP32 Display Puts The Customer First

Most of the projects we feature on Hackaday are built for personal use; designed to meet the needs of the person creating them. If it works for somebody else, then all the better. But occasionally we may find ourselves designing hardware for a paying customer, and as this video from [Proto G] shows, that sometimes means taking the long way around.

The initial task he was given seemed simple enough: build a display that could spin four license plates around, and make it so the speed could be adjusted. So [Proto G] knocked a frame out of some sheet metal, and used an ESP32 to drive two RC-style electronic speed controllers (ESCs) connected to a couple of “pancake” brushless gimbal motors. Since there was no need to accurately position the license plates, it was just a matter of writing some code that would spin the motors in an aesthetically pleasing way.

Unfortunately, the customer then altered the deal. Now they wanted a stand that could stop on each license plate and linger for a bit before moving to the next one. Unfortunately, that meant the ESCs weren’t up to the task. They got dumped in favor of an ODrive motor controller, and encoders were added to the shafts so the ESP32 could keep track of the display’s position. [Proto G] says he still had to work out some kinks, such as how to keep the two motors synchronized and reduce backlash when the spinner stopped on a particular plate, but in the end we think the results look fantastic. Now if only we had some license plates we needed rotisseried…

If [Proto G] knew he needed precise positioning control from the start, he would have approached the project differently and saved himself a lot of time. But such is life when you’re working on contract.

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Phase Shift Pump Control? There’s An App For That.

The sort of pumps used in the filtration systems of fountains and swimming pools don’t take kindly to running dry. So putting such a pump on a simple timer to run while you’re away comes with a certain level of risk: if the pump runs out of water while you’re gone, you might come home to a melted mess. One possible solution is a float sensor to detect the water level in whatever you’re trying to pump, but that can get complicated when you’re talking about something as large as a pool.

For his entry into the 2019 Hackaday Prize, [Luc Brun] is working on controller that can detect when the pump is running dry by monitoring the phase shift between voltage and current. With an inductive load like a pump, the current should lag behind the AC voltage a bit under normal operation. But if they become too far out of phase with each other, that’s a sign that the pump is running in a no-load condition because there’s no water to slow it down.

As [Luc] explains in the project write-up, simply monitoring the pump’s peak current could work, but it would be less reliable. The problem is that different motors have different current consumptions, so unless you calibrated the controller to the specific load it’s protecting, you could get false readings. But the relationship between current and voltage should remain fairly consistent between different motors.

The controller is powered by a Arduino Nano and uses a ACS712 current sensor to take phase measurements. Since he had the ability to toggle the pump on and off with a relay attached to the Arduino, [Luc] decided to add in a few other features. The addition of a DS1307 Real Time Clock means the pump can be run on a schedule, and an HC-05 Bluetooth module lets him monitor the whole system from his smartphone with an Android application he developed.

Since the theme of this year’s Hackaday Prize is designing a product rather than a one-off build, judges will be looking for exactly the sort of forward thinking that [Luc] has demonstrated here. As the controller is currently a mass of individual modules held inside a waterproof enclosure, the next steps for this project will likely be the finalization of the hardware design and the production of a custom PCB.

Battle Tested Current Limiter For Cheap DC Motor Controllers

Running a brushed motor in muddy or dusty environments takes a toll on controllers, with both heavy back EMF and high stall currents. This explains one of the challenge in Europe’s Hacky Racer series, which is decidedly more off-road than America’s Power Racing Series.

In pushing these little electric vehicles to the limits, many builders use brushless Chinese scooter motors since they’re both available and inexpensive. Others take the brushed DC route if they’re lucky enough to score a motor — and then the challenge becomes getting the most performance without burning up your controller. To fix this, [MechanicalCat] has come up with a current limiter for cheap DC motor controllers.

Circuit protection added to motor controller

The full write-up is in the included PDF file, and describes the set-up of an Arduino Nano sitting between throttle and controller, and taking feedback from a current sensor. The controller in question is a 4QD Porter 10 so an extra component is a DC-to-DC converter to provide a floating ground for the Arduino. However, there is also the intriguing possibility of the same set-up being used with absurdly cheap Chinese motor controllers. There is also advice on fitting flyback diodes, something which might have saved one controller in the Hackaday pits last year.

It’s yet to be seen what effect this will have on Hacky Racer competitiveness, however its applications go far beyond that field into anywhere a reliable small DC motor drive on the cheap is required. Meanwhile, if you’re unsure where this Hacky Racer stuff came from, you could start here.