RC car upgraded to Bluetooth control

[Chet] is showing off the Bluetooth controller upgrade for this RC car. The donor vehicle is a rather inexpensive Porche which he purchased to make sure he didn’t start hacking up his more expensive toys.

He took a bit different route than the IOIO RC truck we saw earlier in the week, but the concept is basically the same. That build used an IOIO board with a USB Bluetooth dongle. This one uses an Arduino Mini with a serial Bluetooth module. He patched into the motor driver circuits on the original PCB. While he was at it he also soldered in some LEDs to use as switchable headlights.

There was one issue which he had to overcome. The current draw from the motor starting up would sometimes dip the voltage low enough to reset the Arduino. He tried using a bigger capacitor to feed the board, but in the end opted to add a boost converter.

Scavenging from consumer electronics to make a flame-powered phone charger

[Gigafide] just finished building this flame-powered phone charger. The concept is not new. He grabbed a Peltier cooler and used the temperature differential between a flame and a heat sink to produce electricity used by the charger. If you search around here enough you’ll find plenty of candle-powered devices, and a few hacks that use a Peltier device in a bit more interesting way. But we really like his high-production value video, straightforward explanation of the concepts, and ability to source the components in consumer devices. We don’t think you’ll be disappointed by his video found after the break.

The Peltier device comes out of a USB drink chiller. It is supported by a metal stand made from electrical box covers and threaded rod. Underneath he’s using a gel fuel can used by the food industry, and above he’s got  CPU heat sink and fan. This setup puts out around 1.5V but he’ll need a boost converter to charge a phone with that. A single AA battery charger meant to power your phone in a pinch is perfect for this application.

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Another take on using ‘dead’ batteries

Here’s another circuit that can be used to squeeze the remaining potential from supposedly dead batteries. Just like the AASaver, we see this as a useful prototyping tool, providing juice for a breadboard even though it’s not reliable enough for long-term use (the batteries are just about through after all).

First off, the image above shows rechargeables instead of alkalines. We don’t recommend this as the circuit has no cutoff feature and the 0.7V input for the boost converter surely is below the recommended low-voltage limit for those cells. But that aside, we like the diminutive board which solders onto the end of a battery pack. It uses an SC120SKTRT which is a variable boost regulator capable of outputting 1.8-5V depending on resistor choices. You can leave the resistors off and it will default to 3.3V, set the output explicitly, or roll in some potentiometers and use your multimeter to tune the output.

This regulator costs more than the MCP1640 used in the AASaver, but it appears to use less passive components making for a smaller footprint. At a total of $3.50 plus the PCB (which will be a snap to etch at home) this is another great option to top off your next parts order.

[Thanks Uwe]

Squeezing the juice out of some AA batteries

[Ray’s] breadboard power supply lets you drain the last traces of power from ‘dead’ AA batteries. Electronics that are powered off of disposable alkaline batteries have a cutoff voltage that usually leaves a fair amount of potential within. Since many municipal recycling programs don’t take the disposables (you’re just supposed to throw them in the trash!) we love the idea of squeezing them for prototyping use.

His design uses just one IC, the MCP1640, along with a handful of passive components. The chip is a boost converter with a startup voltage of just 0.65V, which means the batteries themselves – normally starting life above 1.5V – can be used until they drop to about 0.3V each.

Above you can see the kit he is selling. But it’s an open source project and the circuit is so simple we’re sure you can build your own. Add that boost converter chip to your next parts order for around $0.40.

[Ray] made a nice demo video for the device which you can see embedded after the break.

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An introduction to DC boost converters


If you are planning on creating some sort of Nixie tube display, you will undoubtedly need to find yourself a high voltage DC power supply. If you don’t want to add a transformer to your project, you can always opt to build a boost converter instead. [Andrew Moser] shows us just how easy it is to build one, discussing the theory behind simple boost converters along the way.

Boost converters are often driven by dedicated ICs, but in this case the PWM signal from an Arduino does the job just fine. [Andrew] covers the process of choosing the proper components for the circuit, discussing duty cycles and components to avoid lest your boost converter die an untimely death.

He shows us how to implement a feedback system to get a more precise output voltage, but as Lady Ada has shown us, an open loop works pretty well too.

For the beginners that want to just get things up and running, his instructions and code should be sufficient, but [Andrew] provides plenty of reference links for those looking to delve deeper into the subject.

Portable bench supply carries around 10 amp-hours of juice

[Punish3r] wanted to have power for prototyping on the go. What he came up with is this little thing above. Inside you’ll find common components that let the unit provide 10 amp hours of current with a 12V 500mA output.

The storage capacity is provided by a dozen Lithium batteries. These 3.7V cheapies are wired in parallel behind a protection board. For charging and discharging, a Sparkfun LiPo charger board was used, taking care of all the work necessary to top off the batteries using a wall-wort. The final piece in the puzzle is a boost converter that provides the regulated 12v connected to the red and black banana plug receivers on the bottom of the case.

This is very much a plug-and-play design… just make sure you hook the parts up correctly and you’re up and running. We would love to see a roll-your-own boost converter circuit that include a switch or dial that lets you select common PSU voltage levels. If you’re going to the trouble to make your own board you might as well incorporate the charging circuit at the same time.

[Thanks Paul]

OLED displays and small microcontrollers

If you’ve ever thought of utilizing a small and inexpensive OLED display in your project [Rossum] has the details you need to get started. In the past we’ve seen him take a tour of available LCD screens and this is much the same, detailing his look at three different models. In the video after the break each is connected to a driver board that he made. The boards have two important components, the first is a boost driver for the 12-16V input the screens need, the second is an octal buffer necessary if you are using a 5V microcontroller. These take care of the hardware considerations, making it simple to drive them with a chip of your choosing.

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