Building an Electric Scooter That’s Street Legal, Even in Germany

Sometimes a successful project isn’t only about making sure all the electrons are in the right place at the right time, or building something that won’t collapse under its own weight. A lot of projects involve a fair amount of social engineering to be counted as a success, especially those that might result in arrest and incarceration if built as originally planned. Such projects are often referred to as “the fun ones.”

For the past few months, we’ve been following [Bitluni]’s DIY electric scooter build, which had been following the usual trajectory for these things – take a stock unpowered scooter, replace the rear wheel with a 250 W hub motor, add an ESC, battery, and throttle, and away you go. Things took a very interesting turn, however, when his street testing ran afoul of German law, which limits small electric vehicles to a yawn-inducing 6 kph. Unwilling to bore himself to death thus, [Bitluni] found a workaround: vehicles that are only assisted by an electric motor have a much more reasonable speed limit of 25 kph. So he added an Arduino with a gyro and accelerometer module and wrote a program to only power the wheel after the rider has kicked the scooter along a few times – no throttle needed. The motor stops after a bit, needing another push or two to kick it back on. A brake lever kills the motor, as does laying the scooter on its side. It’s quite a clever design, and while it might not keep the Polizei at bay, you can’t say he didn’t try.

[Bitluni] has quite a range of builds, from software-defined television to bad 3D-scanners to precision wine glass whacking. You should check out his stuff. Continue reading “Building an Electric Scooter That’s Street Legal, Even in Germany”

Hybrid Lab Power Supply From Broken Audio Amp

The lab power supply is an essential part of any respectable electronics workbench. However, the cost of buying a unit that has all the features required can be eye-wateringly high for such a seemingly simple device. [The Post Apocalyptic Inventor] has showed us how to build a quality bench power supply from the guts of an old audio amplifier.

We’ve covered our fair share of DIY power supplies here at Hackaday, and despite this one being a year old, it goes the extra mile for a number of reasons. Firstly, many of the expensive and key components are salvaged from a faulty audio amp: the transformer, large heatsink and chassis, as well as miscellaneous capacitors, pots, power resistors and relays. Secondly, this power supply is a hybrid. As well as two outputs from off-the-shelf buck and boost converters, there is also a linear supply. The efficiency of the switching supplies is great for general purpose work, but having a low-ripple linear output on tap for testing RF and audio projects is really handy.

The addition of the linear regulator is covered in a second video, and it’s impressively technically comprehensive. [TPAI] does a great job of explaining the function of all the parts which comprise his linear supply, and builds it up manually from discrete components. To monitor the voltage and current on the front panel, two vintage dial voltmeters are used, after one is converted to an ammeter. It’s these small auxiliary hacks which make this project stand out – another example is the rewiring of the transformer secondary and bridge rectifier to obtain a 38V rail rated for twice the original current.

The Chinese DC-DC switching converters at the heart of this build are pretty popular these days, in fact we’re even seeing open source firmware being developed for them. If you want to find out more about how they operate on a basic level, here’s how a buck converter works, and also the science behind boost converters.

Continue reading “Hybrid Lab Power Supply From Broken Audio Amp”

Hybrid Bench Power Supply Can Also Hit the Road

Everyone needs a bench power supply, and rolling your own has almost become a rite of passage for hackers. For a long time, the platform of choice for such builds seemed to be the ATX power supply from a computer. While we certainly still see those builds, a lot of the action has switched to those cheap eBay programmable DC-DC converters, with their particolored digital displays.

This hybrid bench and portable power supply is a good example of what can be accomplished with these modules, and looks like it might turn out to be a handy tool. [Luke] centered his build around the DPS3003, a constant current and constant voltage buck converter that can take up to 40-VDC input and outputs up to 32 volts at 3 amps. In bench mode, the programmable module is fed from a mains-powered 24-volt switching supply. For portable work, an 18-volt battery from a Makita drill slips into a 3D-printed adapter on the top of the case. The printed part contains a commercial terminal [Luke] scored on eBay, but we’d bet the entire thing could be 3D printed. And no problem if you change power tool brands — just print another adapter.

Those little eBay power supply modules have proven to be an enabling technology, at least judging by the number of clever ways we’ve seen them used lately. From this combination bench PSU and soldering iron supply to a portable PSU perched atop a battery, these things are everywhere. Heck, you can even reflash the firmware and make them do your bidding.

[via Dangerous Prototypes]

Power Supply Choices

Unless you are building a crystal radio or you’ve finally invented that infinite energy machine, any project you do is going to need some sort of power supply. There was a time when a battery was enough, but these days you probably need some sort of regulation. But there are many kinds to choose. Linear, switching, SEPIC, LDO… how do you pick? [Andreas Spiess] has some practical advice in his recent video, which you can see below.

[Andreas] calls the video “Voltage Regulator Cheat Sheet” and that’s an apt name. He covers the major architectures and even points out why you can’t always trust the vendor’s information on certain types of supplies.

Continue reading “Power Supply Choices”

Cleaning up a Low-Cost Buck-Boost Supply

Cheap DC-DC converters have been a boon on the hobbyist bench for a while now, but they can wreak havoc with sensitive circuits if you’re not careful. The problem: noise generated by the switch-mode supply buried within them. Is there anything you can do about the noise?

As it turns out, yes there is, and [Shahriar] at The Signal Path walks us through a basic circuit to reduce noise from DC-DC converters. The module under the knife is a popular buck-boost converter with a wide input range, 0-32 VDC output at up to 5 amps, and a fancy controller with an LCD display. But putting the stock $32 supply on a scope reveals tons of harmonics across a 1 MHz band and overall ripple of about 66 mV. But a simple voltage follower built from a power op-amp and a Zener diode does a great job of reducing the spikes and halving the ripple. The circuit is just a prototype and is meant more as a proof of principle and launching point for further development, and as such it’s far from perfect. The main downside is the four-volt offset from the input voltage; there’s also a broad smear of noise at the high end of the spectrum that persists even with the circuit in place. Centered around 900 MHz as it is, we suspect a cell signal of some sort is getting in. 900 kHz.

If you haven’t checked out the videos at The Signal Path, you really should. [Shahriar] really has a knack for explaining advanced topics in RF engineering, and has a bench to die for. We’ve covered quite a few of his projects before, from salvaging a $2700 spectrum analyzer to multiplexing fiber optic transmissions.

Continue reading “Cleaning up a Low-Cost Buck-Boost Supply”

Lego Boosts Their Robotic Offering

Kids often have their first exposure to robots in school using Lego Mindstorm kits. Now Lego is rolling out Boost — a robotic kit targeting all Lego builders from 7 years old and up. The kit is scheduled to be on the market later this year (it appeared at the recent CES) and will sell for about $160.

[The Brothers Brick] had a chance to try the kit out at CES (see the video below) and you might find their review interesting. The kit provides parts and instructions to build five different models: a cat, a robot, a guitar, a 3D printer, and a tracked vehicle. You can check out the official page, too.

Continue reading “Lego Boosts Their Robotic Offering”

A Buck-Boost Converter from the Ground Up

DC to DC conversion has come a long way. What was once took an electromechanical vibrator and transformer has been reduced to a PC board the size of a largish postage stamp that can be had for a couple of bucks on eBay. So why roll your own buck-boost converter for the ground up? Maybe because sometimes the best way to learn is by doing.

Continue reading “A Buck-Boost Converter from the Ground Up”