LED Driver Circuit For Safety Hat Sucks Single AAA Cell Dry

January 19, 2023 by Donald Papp 21 Comments

[Petteri Aimonen] created an omnidirectional LED safety light to cling to his child’s winter hat in an effort to increase visibility during the dark winter months, but the design is also great example of how to use the Microchip MCP1640 — a regulated DC-DC step-up power supply that can run the LEDs off a single AAA cell. The chip also provides a few neat tricks, like single-button on/off functionality that fully disconnects the load, consuming only 1 µA in standby.

[Petteri]’s design delivers 3 mA to each of eight surface-mount LEDs (which he says is actually a bit too bright) for a total of about 20 hours from one alkaline AAA cell. The single-layer PCB is encased in a clear acrylic and polycarbonate enclosure to resist moisture. A transistor and a few passives allow a SPST switch to act as an on/off switch: a short press turns the unit on, and a long press of about a second turns it back off.

One side effect is that the “off” functionality will no longer work once the AAA cell drained too badly, but [Petteri] optimistically points out that this could be considered a feature: when the unit can no longer be turned off, it’s time to replace the battery!

The usual way to suck a battery dry is to use a Joule Thief, and while this design also lights LEDs, it offers more features and could be adapted for other uses easily. Interested? [Petteri] offers the schematic, KiCAD file for the PCB, and SVG drawing of the enclosure for download near the bottom of the project page.

Toddler EV Gets Big Boy Battery Upgrade

July 29, 2022 by Ryan Flowers 13 Comments

No matter the type of vehicle we drive, it has a battery. Those batteries wear out over time. Even high end EV’s have batteries with a finite life. But when your EV uses Lead Acid batteries, that life is measured on a much shorter scale. This is especially true when the EV is driven by a driver that takes up scarcely more space in their EV than a stuffed tiger toy! Thankfully, the little girl in question has a mechanic:

A 3d printed adapter sends go-juice to the DC-DC converter

Her daddy, [Brian Lough], who documented the swift conversion of his daughter’s toy truck from Lead Acid to Li-Ion in the video which you can see below the break.

Facing challenges similar to that of actual road worthy passenger vehicles, [Brian] teamed up with [bitluni] to solve them. The 12 V SLA battery was being replaced with a 20 V Li-Ion pack from a power tool. A 3d printed adapter was enlisted to break out the power pins on the pack. The excessive voltage was handled with a DC-to-DC converter that, after a bit of tweaking, was putting out a solid 12 V.

What we love about the hack is that it’s one anybody can do, and it gives an inkling of what type of engineering goes into even larger projects. And be sure to watch the video to the end for the adorable and giggly results!

Speaking of larger projects, check out the reverse engineering required in this Lead Acid to Li-Ion conversion we covered in 2016.

Continue reading “Toddler EV Gets Big Boy Battery Upgrade” →

Wireless Earbuds Charge Themselves

August 11, 2021 by Bryan Cockfield 20 Comments

As more and more ports are removed from our smart devices, it seems that we have one of two options available for using peripherals: either buy a dongle to continue to use wired devices, or switch to Bluetooth and deal with perpetually maintaining batteries. If neither of these options suits you, though, there’s a third option available as [befinitiv] shows us in this build where he integrates a tiny solar panel to his earbud case to allow them to automatically charge themselves.

To start, he begins by taking apart the earbud case. For those who still haven’t tried out a set of these, they typically charge only when placed inside of their carrying case, which in his case also contains a small battery itself. Soldering wires directly to the battery allow for the battery to charge without as much electrical loss as he would have had if he had connected to the USB pins on the circuit board. Even then, the cell only generates a single volt so he needs a 5V boost converter to properly charge the battery. That came with its own problem, though, as it wouldn’t fit into the case properly. To solve that issue, he desoldered all of the components and deadbugged them together in order to fit the converter into a much smaller space without having to modify the case in any other way.

With all of that done and the small solar cell attached to the case, [befinitiv] has a smart solution to keep his wireless earbuds topped up without having to carry cables or dongles around every day. We’ve seen plenty of interesting solutions to the problem of various electronics manufacturers removing the ubiquitous 3.5 mm headphone jack too, and not all of them have dealt with this problem without certain other quirks arising as a result.

Continue reading “Wireless Earbuds Charge Themselves” →

Bench Supplies Get Smaller Thanks To USB-C

October 19, 2020 by Bryan Cockfield 17 Comments

Bench power supplies are an indispensable tool when prototyping electronics. Being able to set custom voltages and having some sort of current limiting feature are key to making sure that the smoke stays inside all of the parts. Buying a modern bench supply might be a little too expensive though, and converting an ATX power supply can be janky and unreliable. Thanks to the miracle of USB-C, though, you can build your own fully-featured benchtop power supply like [Brian] did without taking up hardly any space, and for only around $12.

USB-C can be used to deliver up to 100W but is limited to a few set voltage levels. For voltages that USB-C doesn’t support, [Brian] turns to an inexpensive ZK-4KX buck-boost DC-DC converter that allows for millivolt-level precision for his supply’s output. Another key aspect of using USB-C is making sure that your power supply can correctly negotiate for the amount of power that it needs. There’s an electronic handshake that goes on over the USB connection, and without it there’s not a useful amount of power that can be delivered. This build includes a small chip for performing this negotiation as well.

With all the electronics taken care of, [Brian] houses all of this in a 3D-printed enclosure complete with a set of banana plugs. While it may not be able to provide the wattage of a modern production unit, for most smaller use cases this would work perfectly. If you already have an ATX supply around, though, you can modify [Brian]’s build using that as the supply and case too.

Continue reading “Bench Supplies Get Smaller Thanks To USB-C” →

A Simple Soft Power Switch Using Common Modules

July 21, 2020 by Tom Nardi 28 Comments

If you want to easily control the power in a circuit, you’ll probably reach for the classic toggle switch. While there’s certainly nothing wrong with that, physical toggles are a bit dated at this point. A soft power switch that turns your gadget on and off at the tap of a finger is far more 21st century. You might think this kind of modern trickery is too difficult to implement on a DIY project, but as [Sasa Karanovic] shows, it’s actually a lot easier than you might think.

Now to be fair, that wasn’t actually his goal. All [Sasa] was trying to do was come up with a slick way to control the LED lighting in his 3D printer enclosure. Which, as you can see in the video below, he accomplished. But the hacked together circuit he used to do it could easily be adapted for other electronic projects. If you’re using a LM2596 DC-DC converter module to power your gadget, you can add a touch sensitive soft switch for literally pennies.

The trick is utilizing the enable pin on the LM2596. The common buck converter modules tie this pin to ground so the regulator is always enabled, but if you lift the pin off the PCB and connect it to the output of a TTP223 capacitive touch sensor, you can simply tap the pad to control the regulator. Power for the touch sensor itself is pulled from the input side of the regulator, so even when the power is cut off downstream, the sensor is still awake and can kick the chip back into gear when you need it.

If you’re not interested in touch control, you could try connecting the enable pin on the regulator to an ESP8266 and making a cheap Internet-controlled DC power supply. Continue reading “A Simple Soft Power Switch Using Common Modules” →

DIY Magsafe Charger Feeds Off 12 V Solar Battery

April 19, 2020 by Donald Papp 18 Comments

[Steve Chamberlin] has a spiffy solar-charged 12 V battery that he was eager to use to power his laptop, but ran into a glitch. His MacBook Pro uses Apple’s MagSafe 2 connector for power, but plugging the AC adapter into the battery via a 110 VAC inverter seemed awfully inefficient. It would be much better to plug it into the battery directly, but that also was a problem. While Apple has a number of DC power adapters intended for automotive use, none exist for the MagSafe 2 connector [Steve]’s mid-2014 MacBook Pro uses. His solution was to roll his own MagSafe charger with 12 VDC input.

Since MagSafe connectors are proprietary, his first duty was to salvage one from a broken wall charger. After cleaning up the wires and repairing any frayed bits, it was time to choose a DC-DC converter to go between the MagSafe connector and the battery. The battery is nominally 12 volts, so the input of the DC-DC converter was easy to choose, but the output was a bit uncertain. Figuring out what the MagSafe connector expects took a little educated guesswork.

The original AC adapter attached to the charger claimed an output of 20 volts, another Apple adapter claimed a 14.85 V output, and a third-party adapter said 16.5 volts. [Steve] figured that the MagSafe connectors seemed fine with anything in the 15 to 20 V range, so it would be acceptable to use a 12 V to 19 V DC-DC boost converter which he had available. The result worked just fine, and [Steve] took measurements to verify that it is in fact much more efficient than had he took the easy way out with the inverter.

MagSafe has been displaced by USB-C nowadays, but there are plenty of MagSafe devices still kicking around. In a pinch, keep in mind that a little bit of filing or grinding is all that’s needed to turn MagSafe 1 into MagSafe 2.

Bench Power Supply Packs A Lot Into A DIN-Rail Package

August 18, 2018 by Dan Maloney 8 Comments

We’re not sure why we’ve got a thing for DIN-rail mounted projects, but we do. Perhaps it’s because we’ve seen so many cool industrial control cabinets, or maybe the forced neatness of DIN-mounted components resonates on some deep level. Whatever it is, if it’s DIN-rail mounted, chances are good that we’ll like it.

Take this DIN-mounted bench power supply, for instance. On the face of it, [TD-er]’s project is yet another bench supply built around those ubiquitous DPS switching power supply modules, the ones with the colorful displays. Simply throwing one of those in a DIN-mount enclosure isn’t much to write home about, but there’s more to this project than that. [TD-er] needed some fixed voltages in addition to the adjustable output, so a multi-voltage DC-DC converter board was included inside the case as well. The supply has 3.3, 5, and 12 volt fixed outputs along with the adjustable supply, and thanks to an enclosed Bluetooth module, the whole thing can be controlled from his phone. Plus it fits nicely in a compact work area, which is a nice feature.

We haven’t seen a lot of DIN-rail love around these pages — just this recent rotary phase converter with very tidy DIN-mounted controls. That’s a shame, we’d love to see more.