Category: less is more
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…
Ognite Digital Candle Finally Reaches Beta 2
This new version is wildly more power efficient, so an Ognite should now be able to run continuously for months on a couple of AA batteries. You can read all about the Ognite here…
…and about the update progress here…
Now if I can just find a solution to the battery holder problem, this project can finally go into production. Anyone?