Sensirion’s SHTxx is a digitally interfaced humidity and temperature sensor. Accurate humidity measurements usually require careful analog design, but the SHTxx moves all that complicated stuff into a single chip. Through-hole (SHT7x) and surface mount (SHT1x) versions are available, we used the surface mount SHT11 with +/-3% accuracy. We’ll show you how to use the SHTxx below.
Continue reading “Parts: Precision Humidity And Temperature Sensor (SHT1x/7x)”
Sometimes a project has more sensors, buttons, or LEDs than your microcontroller has pins. The PCF8574 is an easy way to add 8 low-speed input or output pins to a microcontroller. A configurable address lets multiple PCF8574s exist on the same bus, so two microcontroller pins can control dozens of IO pins. We’ll show you how to use this chip below.
When the RepRap team found themselves pushing the limits of the Arduino, they started looking for alternatives. They found it in the ATMega644P. It has four times the memory and four times the RAM compared to the ATMega168 used in the standard Arduino. It also has 32 I/O pins. They ported the Arduino software to the microcontroller and started producing Sanguino boards. Now that the base design is nailed down, they’ve begun expanding it to their specific purpose. Pictured above is a prototype RepRap motherboard. While the Sanguino is barebones, this board has onboard connectors for all of the RepRap’s motors, so you can just plug it in. It is also designed to support the future Generation 3 electronics. Probably the most interesting feature is the SD card slot. The goal is to eventually have a board that can run the RepRap without a host computer if necessary; it will manufacture designs directly from the flash card.
The Maxim DS2431 1K EEPROM is 1-Wire device that adds storage to a project using a single microcontroller pin. We previously interfaced a 1-wire thermometer, but this EEPROM is slightly different because it draws power directly from the 1-Wire bus. Grab the datasheet (PDF) and follow along while we read and write this simple 1-Wire memory.
Robot Magazine has a great article about how to machine custom robot parts. In this article [Matt Bauer] shows the basics of making custom robot parts and skeletal brackets for his humanoid robot creations using a CNC mini-mill. He uses a custom jig overlay designed to make cutting thin sheet stock much easier and to protect his equipment. This template concept creates a platform for many other custom parts going forward. [Matt] includes the .nc g-code files as well as a “how-to” PDF in a ZIP file.
Atanua is a real time logic simulator to help people learn some of the basics of electronics. Focusing mainly on logic, as opposed to power, this is a fantastic tool to learn with. They have done a fantastic job of making it easy to use as well as good looking. We can see this as being a must have piece of software for any hacker. There is a free version available as long as you aren’t using it commercially.
[Thanks ellisgl]
[Alexander.m] shows us how to do a major overhaul on a cordless drill, replacing pretty much everything but the case. He needed some more power, but found the price tag of the bigger drills to be prohibitive. He opted for a more hacked together approach and used a 24 volt 1.4 hp hobby motor as a drive. He had to make a custom enclosure for the batteries too. The final result may not be the prettiest thing in the world, with that giant battery pack on the bottom, but it probably gets the job done pretty well and cost less than half of what a new one would have.
