Category: hardware
Ghost Guitar – Self Strumming Strings
Normally fingers provide the force needed to set a guitar’s strings vibrating, but with some simple electronics we can make a self-strumming guitar that plays itself without any moving parts at all. It is better than magic- its physics! Click on for a full explanation of how it works and a video of the ghost guitar rocking itself out (it really does make some creepy and spooky sounds)…
Plates vs Coils – An alternative approach to wireless power transmission
Inductive power transfer is all the rage. There are now easy chips that do all the hard work for you. It even came built-in on my new phone!
But what about capacitive power transmission?
How come I’ve never seen a product that uses plates rather than coils? Is capacitive power transfer possible? Practical? Let’s break out a roll of tinfoil and find out!
AVR Timer-based One Shot Explained
Last time, we made one-shot pulses using the AVR’s built in hardware timer module. Today we are going to dive deep into the datasheets to see how this technique is able to coax the normally free-running timer into generating a single pulse. Along the way, we will learn about the low level rules that govern the operation of the timer, and use a trick or two to get around those rules. Read on!…
The Perfect Pulse- generating precise one-shots on AVR8
It is possible to generate one-shot pulses on an AVR that…
- Are as narrow as a single clock cycle (63 nanoseconds!)
- Are precise to a single clock cycle
- Will run to correct completion no matter what else the processor is doing 1
- Do not require you to turn off interrupts at all (!)
- Do not require any assembly code
These pulses are generated in pure hardware. They require a couple of instructions of interruptible code to fire. Once fired, they are completely autonomous and depend only on the system clock to run to completion.
Sound cool? Read on!
Easy hack to allow an AVR Dragon to power the target device over the ISP cable
I’ve been a big fan of the SparkFun Pocket AVR programmer, partly because it has a handy little switch that lets you send power to the target device…
Unfortunately, I started getting “Error: Could not find USBtiny device” while programming boards using a jig…
A tale of Four USB power supplies
No time for commentary here, just pretty pictures of the insides and outputs of some cheap USB wall adapters.
The Contenders
Battery Fuel Gauge with Zero Parts and Zero Pins on AVR
It can be nice to know how much battery power you have. It becomes critically important with LiPo batteries since you can permanently damage them by running the voltage down too low. Typically battery voltage detection requires adding a circuit with extra parts and their associated power requirements. Wouldn’t it be great to be able to do this using nothing but software? Read on for a no parts, no pins, no power solution…
Inside Neouart – Tricking a serial port into being a signal generator
Last time, we connected a NeoPixel directly to a RaspberryPi. This is certainly fun and useful, but the real motivation behind this project was to explore clever ways to make use of limited hardware resources. NeoPixels need a precisely timed string of bits to be happy. Luckily, every RaspPi comes with built-in hardware for generating strings of precisely timed bits – a serial port!
If all you care about is making pretty colors the easy way, don’t bother reading this article. If you are wondering how it is possible to reliably generate a pulse train with +/-150ns precision on a Raspberry Pi pin without kernel mods or DMA, then read on!
Save the Earth One Resistor at a Time – External pull-up resistor no longer needed for DS18B20 temp sensor
EXECUTIVE SUMMARY:
Using the updated Arduino 1-Wire library code presented here, you can eliminate the need for an external pull-up resistor for typical small networks of DS18B20 temperature sensors. This should also work with any AVR processor and other types of 1-Wire devices as well. You can download the updated 1-Wire library here…
https://github.com/bigjosh/OneWireNoResistor/archive/master.zip
The mythical “required” external pull-up
From the DS18B20 Data Sheet
If you’ve ever used the ubiquitous (and amazingly useful!) DS18B20 family of 1-Wire temperature sensors, you’ve almost certainly used a 4.7K ohm pull-up resistor as well. Every one of the seemingly endless Arduino DS18B20 tutorials on the web starts with some version of the line “You will not be able to do anything with this senor until you go out and procure yourself a 4.7K ohm resistor”. AdaFruit is even generous enough to include one of these resistors with every DS18B20-based temperature sensor they sell (be it bare, waterproof, or hi-temp) because they know you are going to need it.
I am here to tell you that everything is about to change. If you were banking on your stockpiles of 4.7K ohm resistors to be the one reliable store of value in these uncertain times, you need to rethink your long-term asset preservation strategy because the decade-long run of stable demand for this part is about to plummet. Yes – it is now possible to connect DS18B20 sensors without any external pull-up resistor at all!
Outrageous claims demand outrageous proof, so let’s start with a brief demo that proves beyond a shadow of a doubt that this is not just a cockamamie theory, but cold hard fact…
Temperature Logging to a Google Spreadsheet with an Arduino Yun
| UPDATE 8/7/2104:It appears that Google occasionally will randomly and silently drop the authorization for an Apps Script web app. If you notice that your spreadsheet has stopped updating and you know that your logger is still working, then you probably need to log into your spreadsheet from a web browser, go into the scripts editor, and manually execute any function in the script. This will cause a popup that will reauthorize the script and everything will then start working again.
I think this is the last straw. I can not recommend using Google for logging (or any other non-trivial application) any more. This stuff is just too flaky. Sorry. |
If you are like me, you often find yourself in a situation where you need to log multiple channels of temperature data. From testing nano-insulating paint to debugging an overheating geothermal well, most of us will have need of accurate and frequent temperature logs at some point in our short and brutish lives.
Here is a recipe to make a reliable, cheap, and easy cloud-based, multi-channel temperature logger using an Arduino Yun and DS18B20 temperature sensors. I chose the Yun because everyone loves Arduinos and this one can connect to the internets. I choose the DS18B20 sensors because they are awesome and cheap and accurate and you can hook up lots of them to a single pair of wires.