It’s Never Been Easier To Build A WiFi-Controlled RC Car

March 24, 2024 by 14 Comments

Today, wireless-enabled microcontrollers are everywhere and can be had for just a few bucks. You can use them to build all kinds of connected projects more cheaply than ever before. [ROBO HUB] demonstrates this well with an incredibly simple WiFi-controlled RC car build.

The build is based around an NodeMCU ESP8266 microcontroller, paired with an L293D motor driver. This lets the microcontroller drive brushed DC motors for differential drive. Power is courtesy of three 18650 lithium-ion batteries. These parts are assembled into a 3D-printed car of sorts with four wheels. The drivetrain is rather odd, with gear motors installed on the two front wheels, and simple brushed DC motors installed on the two rear wheels. The motors on each side are paired together so the vehicle has tank-style steering.

Meanwhile, the ESP8266 is programmed so it can be controlled via a smartphone app. The touchscreen controls are not as elegant as toy RC cars of years past, but it’s pretty good for a cheap DIY build.

It’s a fairly simple project and one that any high-school student could follow along to learn something. Projects like these can be a great way to learn about everything from mechanics to electronics and even basic programming. It may not be complicated, but that makes it a great learning tool. We see a ton of projects like this on the regular, and every time they’re built, somebody is picking up some new skills.

We’ve been talking about WiFi-controlled RC cars for a long time. Way back when it was nowhere near this easy. Video after the break. Continue reading “It’s Never Been Easier To Build A WiFi-Controlled RC Car” →

a DIY smoke grenade pours out smoke from a vape pen assembly

R/C Smoke Grenade Rolls With The Changes

March 22, 2024 by 9 Comments

[Davis DeWitt] gets to do something that many of us only dream of — build cool working props for movies. This time, the director asked for a realistic smoke grenade that can roll up to a mark and stop on it every take, pouring out smoke the entire time.

The innards of a DIY remote control smoke grenade.

[Davis] decided on a hamster ball-esque design that uses a pair of motors that he can control remotely, plus the innards from a vape pen and a tiny fan to distribute the smoke. The motors spin 3D printed wheels using printed gears attached to the shafts, which drive the whole assembly forward or backward.

In order to get everything to fit inside the printed canister, [Davis] had to use the smallest components he could find, like the Seeed Xiao SAMD21 and the DRV8833 motor driver. The whole thing is powered by a pair of 18650s, which, as you might imagine, really factored into the weight distribution scheme. In this case, the batteries act as a pendulum and keep the inner assembly level and not spinning wildly inside the canister.

Finally, it was time for the smoke grenade aesthetics. After what seemed like endless sanding, priming, and masking, [Davis] had a really good-looking smoke grenade that just needed some vinyl lettering and fake wear-and-tear to be complete. Be sure to check it out in action after the break.

We don’t see a lot of grenades around here, but when we do, they’re often keyboards.

Continue reading “R/C Smoke Grenade Rolls With The Changes” →

Lithium-Ion Batteries Power Your Devboards Easily

March 14, 2024 by 24 Comments

Last summer, I was hanging out with a friend from Netherlands for a week, and in the middle of that week, we decided to go on a 20 km bike trip to a nearby beach. Problem? We wanted to chat throughout the trip, but the wind noise was loud, and screaming at each other while cycling wouldn’t have been fun. I had some walkie-talkie software in mind, but only a single battery-powered Pi in my possession. So, I went into my workshop room, and half an hour later, walked out with a Pi Zero wrapped in a few cables.

I wish I could tell you that it worked out wonders. The Zero didn’t have enough CPU power, I only had single-core ones spare, and the software I had in mind would start to badly stutter every time we tried to run it in bidirectional mode. But the battery power solution was fantastic. If you need your hack to go mobile, read on.

Continue reading “Lithium-Ion Batteries Power Your Devboards Easily” →

Garden Light Turned Mesh Network Node

January 21, 2024 by 10 Comments

We love a good deal, especially when it comes to scavenging parts for projects. Cheap outdoor solar lights are more than just garden accessories; they’re a handy source of waterproof enclosures, solar panels and batteries. This is demonstrated by [Tavis], who turned one such light into a Meshtastic LoRa communication node.

Solar Light With Meshtastic node inside
Where there’s an antenna, there’s a radio

A nice feature on this specific $15 Harbor Breeze Solar LED is the roomy solar panel enclosure with integrated 18650 battery holder, allowing for easy battery swaps. [Tavis] was able to easily fit the RAKwireless modular dev board, and wire it into the light’s charging circuit. The cheap  circuit is likely not the most efficient, but will probably get the job done. It’s always possible to just swap it out with a better charging board. [Tavis] also added an external antenna by using a panel-mount SMA pigtail connector.

The Meshtastic project is all about enabling text-only communications through LoRa-based mesh networks, built using off-the-shelf devices and development boards that won’t break the bank. The project has seen some incredible growth, with people all over the world setting up their own networks.

It’s not the first time we’ve seen garden lights get used in project. We’ve seen MQTT added to a PIR solar light with some clever power saving circuitry, and as a power source for Attiny85-based projects.

Current-Based Side-Channel Attacks, Two Ways

January 4, 2024 by 9 Comments

Funny things can happen when a security researcher and an electronics engineer specializing in high-speed circuits get together. At least they did when [Limpkin] met [Roman], which resulted in two interesting hardware solutions for side-channel attacks.

As [Limpkin] relates it, the tale began when he shared an office with [Roman Korkikian], a security researcher looking into current-based attacks on the crypto engine inside ESP32s. The idea goes that by monitoring the current consumption of the processor during cryptographic operations, you can derive enough data to figure out how it works. It’s difficult to tease a useful signal from the noise, though, and [Roman]’s setup with long wire runs and a noisy current probe wasn’t helping at all. So [Limpkin] decided to pitch in.

The first board he designed was based on a balun, which he used to isolate the device under test from the amplification stage. He found a 1:8 balun, normally used to match impedances in RF circuits, and used its primary as a shunt resistance between the power supply — a CR1220 coin cell — and the DUT. The amplifier stage is a pair of low-noise RF amps; a variable attenuator was added between the amp stages on a second version of the board.

Board number two took a different tack; rather than use a balun, [Limpkin] chose a simple shunt resistor with a few twists. To measure the low-current signal on top of the ESP32’s baseline draw would require such a large shunt resistor that the microcontroller wouldn’t even boot, so he instead used an OPA855 wideband low-noise op-amp as an amplified shunt. The output of that stage goes through the same variable attenuator as the first board, and then to another OPA855 gain stage. The board is entirely battery-powered, relying on nice, quiet 18650s to power both the DUT and the shunt.

How well does it work? We’ll let you watch the talk below and make up your own mind, but since they’ve used these simple circuits to break a range of different chips, we’d say this approach a winner.

Continue reading “Current-Based Side-Channel Attacks, Two Ways” →

Open Source DC UPS Keeps The Low-Voltage Gear Going

December 22, 2023 by 27 Comments

We all like to keep our network gear running during a power outage — trouble is, your standard consumer-grade uninterruptible power supply (UPS) tends to be overkill for routers and such. Their outlet strips built quickly get crowded with wall-warts, and why bother converting from DC to AC only to convert back again?

This common conundrum is the inspiration for [Walker]’s DC UPS design, which has some interesting features. First off, the design is open source, which of course invites tinkering and repurposing. The UPS is built for a 12 volt supply and load, but that obviously can be changed to suit your needs. The battery bank is a 4S3P design using 18650 cells, and that could be customized as well. There’s an ideal diode controller that prevents DC from back-feeding into the supply when the lights go out, and a really interesting synchronous buck-boost converter in place of the power management chip you’d normally see in a UPS. The converter chip takes a PWM signal from an RP2040; there’s also an ESP32 onboard for web server and UI duties as well as an STM32 to run the BMS. The video below discusses the design and shows a little of the build.

We’ve seen a spate of DC UPS designs lately, some more elaborate than others. This one has quite a few interesting chips that most of us don’t normally deal with, and it’s nice to see how they’re used in a practical design.

Continue reading “Open Source DC UPS Keeps The Low-Voltage Gear Going” →

Second Life UPS Mark II: A UPS For Low-Voltage DC Applications

December 17, 2023 by 17 Comments

When you have a whole stack of devices and appliances that all have an AC to DC adapter and which you’d like to put on an uninterruptable power supply (UPS), you could do the obvious thing and get an off-the-shelf UPS with myriad AC outputs. In the case of a 19″ rack this means wrangling a power strip or two and any combination of differently sized AC/DC adapters into the rack, with questionable efficiency and waste heat dumped into the rack. This is where a DC-only UPS like [Maciej Grela]’s Second Life UPS Mark II provides an interesting alternative.

At its core it’s a pretty simple concept: A single 400Watt power supply handles the AC/DC conversion from mains to 24 VDC, which feeds the battery charger as well as the outputs. These outputs include 5 VDC, 12 VDC and Vrail, with the latter being either the output from the PSU, or the battery voltage. In case of AC power failure, an LT4416 dual power path controller handles the switch-over from the PSU output to the internal batteries. In the article, [Maciej] covers how the buck modules for the 12 & 5 VDC rails were sized, along with the conversion of an old rack-mounted network switch into a UPS. Continue reading “Second Life UPS Mark II: A UPS For Low-Voltage DC Applications” →