Wooden pallets are a versatile and widely-available starting point for a multitude of projects. Best of all, they can usually be acquired free of charge. But choose the wrong kind of pallet and you could end up paying dearly. [Eric] has compiled a great deal of useful information about pallets that will help you find ideal candidates and prepare them for whatever project you have in mind, be it a coffee table or a backyard roller coaster.
Pallets come in several styles and loader configurations. Some are made with space between the boards, and others are closed. If you take nothing else away from his article, just remember to look for plain, untinted pallets with no markings and you’ll be fine.
No markings means the pallet was used domestically, so markings aren’t required. Marked pallets from abroad should feature the IPPC logo as well as a treatment code indicating the method used on the material. Debarked (DB), heat treated (HT), and pallets with the European Pallet Association logo (EPAL) are all safe choices. Pallets labeled (MB) were treated with methyl bromide, which is a poisonous fungicide. Colored pallets should be avoided as well. If you find one in a cool color, take a picture of it and find some paint in a similar hue.
Safe pallets can be had from many places ranging from hardware stores to feed and tack supply stores. Find someone you can ask for permission to take pallets—they might even help you load them. Keep some gloves in your trunk to avoid splinters.
Once again, [Afroman] is here for you, this time breaking down electrolyte and the terminology behind batteries.
Volts and Amps are easy mode, but what about Amp hours? They’re not coulombs per second hours, because that wouldn’t make any sense. An Amp hour is a completely different
unit podcast, where a 1Ah battery can supply one amp for one hour, or two amps for 30 minutes, or 500 mA for two hours.
Okay, what if you take two batteries and put them in series? That would double the voltage, but have the same Ah rating as a single cell. Does this mean there is the same amount of energy in two batteries as what is found in a single cell? No, so we need a new unit: the Watt hour. That’s Volts times Amp hours, or more incorrectly, one joule per second hour.
Now it’s a question of the number of cells in a battery. What’s the terminology for the number of cells? S. If there are three cells in a battery, that battery has a 3S rating. You would think that C would be the best letter of the alphabet to use for this metric, but C is entirely different. Nothing here makes any sense at all.
What is C? That’s related to the number of amps a battery can discharge safely. If a 20C battery can discharge 2200mAh, it can deliver a maximum current of 44 A, with 20C times 2.2Ah being 44A.
So there you go. A complete description of something you can’t use logic and inference to reason through. Video below.
Continue reading “A Description of Maddening Battery Terminology”
Although [pinomelean’s] Lithium-ion battery guide sounds like the topic is a bit specific, you’ll find a number of rechargeable battery basics discussed at length. Don’t know what a C-rate is? Pfffft. Roll up those sleeves and let’s dive into some theory.
As if you needed a reminder, many lithium battery types are prone to outbursts if mishandled: a proper charging technique is essential. [pinomelean] provides a detailed breakdown of the typical stages involved in a charge cycle and offers some tips on the advantages to lower voltage thresholds before turning his attention to the practical side: designing your own charger circuit from scratch.
The circuit itself is based around a handful of LM324 op-amps, creating a current and voltage-limited power supply. Voltage limits to 4.2V, and current is adjustable: from 160mA to 1600mA. This charger may take a few hours to juice up your batteries, but it does so safely, and [pinomelean’s] step-by-step description of the device helps illustrate exactly how the process works.
If you need to regulate your power input down to a reasonable voltage for a project, you reach for a switching regulator, or failing that, an inefficient linear regulator. What if you need to boost the voltage inside a project? It’s boost converter time, and Afrotechmods is here to show you how they work.
In its simplest form, a boost converter can be built from only an inductor, a diode, a capacitor, and a transistor. By switching the transistor on and off with varying duty cycles, energy is stored in the inductor, and then sent straight to the capacitor. Calculating the values for the duty cycle, frequency, inductor, and the other various parts of a boost converter means a whole bunch of math, but following the recommended layout in the datasheets for boost and switching converters is generally good enough.
[Afroman]’s example circuit for this tutorial is a simple boost converter built around an LT1370 switching regulator. In addition to that there’s also a small regulator, diode, a few big caps and resistors, and a pot for the feedback pin. This is all you need to build a simple boost converter, and the pot tied to the feedback pin varies the duty cycle of the regulator, changing the output voltage.
It’s an extremely efficient way to boost voltage, measured by [Afroman] at over 80%. It’s also exceptionally easy to build, with just a handful of parts soldered directly onto a piece of perfboard.
Continue reading “Afroman Demonstrates Boost Converters”
The last year has brought us CC3000 WiFi module from TI, and recently the improved CC3200 that includes an integrated microcontroller. The Chinese design houses have gotten the hint, putting out the exceptionally cheap ESP8266, a serial to WiFi bridge that also includes a microcontroller to handle the TCP/IP stack and the software side of an 802.11 connection. Now there’s another dedicated WiFi module. It’s called the MT7681, and it’s exactly what you would expect given the competition: a programmable module with the ability to connect to a WiFi network.
Like TI’s CC3200, and the ESP8266, the MT7681 can be connected to any microcontroller over a serial connection, making it a serial to WiFi bridge. This module also contains a user-programmable microcontroller, meaning you don’t need to connect an Arduino to blink a few pins; UART, SPI, and a few GPIO pins are right on the board. The module also includes an SDK and gnu compiler, so development of custom code running on this module should be easier than some of the other alternatives.
You can pick up one of the MT7681 modules through the usual channels, but there’s an Indiegogo campaign based in China that takes this module and builds a ‘dock’ around it. The dock has a relay, temperature/humidity sensor, a few GPIO pins, and a USB serial connection for use as an Internet of Things base station.
For anyone looking for a little more computational horsepower, there’s also a few mentions and press releases announcing another module, the MT7688, This is a very small (12mm by 12mm) module running Linux with 256 MB of RAM and 802.11n support. This module hasn’t even hit the market yet, but we’ll be on the lookout for when it will be released.
Thanks [uhrheber] for sending this one in.
A few weeks ago we caught wind of a very cool new chip. It’s called the ESP8266, and it’s a WiFi module that allows you to connect just about any project to an 802.11 b/g/n network. It also costs $5. Yes, there was much rejoicing when this chip was announced.
Since we learned of the ESP8266, there has been a lot of work done to translate the datasheets from Chinese, figure out how the SOC can be programmed, and a few preliminary attempts at getting this module working with an Arduino. Keep in mind, very few people have one of these modules in hand right now, so all this information is completely untested. Here’s what we have so far:
Over on Hackaday Projects, [bafeigum] has been working to research the capabilities of this module. Most of the comments deal with the AT Command set for the module and figuring out what is actually returned when certain commands are called.
The ESP8266 community forum is about a week old, but already there’s a wealth of information. Most of the efforts seem to be centered on getting GCC to program this chip, something that would make the ESP8266 a single-solution chip for anything that needs WiFi and a bit of processing power. Everyone (including the great [Sprite_TM]) has currently hit a roadblock, so if you have a ton of experience with GCC and the Xtensa microcontroller, check out that thread. Failing that, we’ll have to wait until someone from Tensilica, the company behind the guts of this chip, to chime in and help everyone figure out how this thing actually works.
The Arduino-heads out there will have a much easier time. There’s already a tutorial for using the ESP8266 as a serial WiFi module. Note the ESP operates on 3.3 Volts, so connecting this module to the 5V pin means you’ll be out $5 and several weeks of shipping time.
This is an incredible amount of development in a very short amount of time, made even more remarkable by the fact that no one has one of these WiFi modules yet. When these modules do arrive to workbenches around the world, we’ll expect the Hackaday tip line to be flooded with very small and somewhat battery friendly WiFi builds.
For his Beyond Unboxing series, [Charles] tore apart a Ryobi cordless chainsaw to get a better look at how this battery powered tool works.
Inside he found a three-phase motor and controller. This motor looks like it could be useful in other projects since it has a standard shaft. The battery pack was popped open to reveal a set of LG Chem 21865 cells, and some management hardware.
With all the parts liberated from the original enclosure, [Charles] set up the motor, controller, and battery on the bench. With a scope connected, some characterization of the motor could be done. A load was applied by grabbing the spinning shaft with welding gloves. [Charles] admits that this isn’t the safest way to test a motor.
While it is a very fast motor, the cut-in speed was found to be rather low. That means it can’t start a vehicle from a stop, but could be useful on e-bikes or scooters which are push started.
This chainsaw a $200 motor, controller, and battery set that could be the basis of a DIY scooter. It sounds great too, as the video after the break demonstrates.
[Thanks to Dane for the tip!]
Continue reading “Electric Chainsaw Teardown”