This was actually the first time I ever needed to multiplex analog channels so it was a good opportunity to learn how to use them. My task was to measure the temperature of 32 thermistors (NTC) with a microcontroller and later process that data. Obviously you cant find that much analog input channels on your common microcontroller so you need to multiplex the signals. First I looked for large analog multiplexers with 16 input channels but those are way too expensive. As it turns out its cheaper to use more smaller 8ch multiplexers(example Digikey pricing: 2pcs 16:1 mux from TI is $7.84 while 3pcs of 8:1 mux from TI is $1.53). I was able to get the 74HC4051 at a good price so I started creating the design around it.
74HC4051 Analog Multiplexer - [Link]
A lot of times we need to keep track of data from a device or a sensor located in a remote location from the point where it is processed. In other situations we desire wireless solutions for ease. Using long cables, infrared (IR) or other means are often tedious and not loss-less. Imagine collecting pH level data from a chemically lethal or toxic treatment plant where human presence is highly health hazardous. Running long cables from the pH sensor to the control or monitor station will surely introduce noisy signals and signal-to-noise ratio will thus drastically decrease. The result is erroneous data acquisition and thereby false decisions may be generated. If infrared signals or other optical means including lasers are used, they will need good obstacle-free line of sight or expensive and delicate optical fibers. Thus the solution stays in the radio frequency (RF) domain. This article talks about interfacing low cost RF modules (KST-TX01 and KST-RX806) for transmitting data between two remotely located PIC microcontrollers.
Wireless data transmission between two microcontrollers using KST-TX01 and KST-RX806 rf modules - [Link]
Rob writes in… [via]
I’ve seen quite a few hacks related to controlling appliances, lights, etc over the years and just wanted to share a little info so that everyone has access to a cheap way to do it relatively safely. By trade I work in the building controls/integration industry and as a result I use these relays at work and at home(chicken coop control,light,etc)quite a bit.
The interface between your microcontroller of choice and the relay is a simple 555 relay driver circuit. I have included the pdf that inspired me to do it this way. The relay I use is the RIBTU1C. The reason I prefer this relay is that the coil will run on 9VC @ 20mA and the contacts will switch 10A @ 120VAC. Total cost for the RIB and a 555 is under $15 if you shop around. In addition the RIB has a partition inside the box between the line and control sides. There’s also room for a Radio Shack breadboard in there!
Safety First! Switching 120vac loads with a microcontroller - [Link]
PIC microcontrollers’ Sleep feature is an extremely useful mechanism to minimize power consumption in battery-powered applications. This experimental tutorial from Embedded Lab describes how to put a PIC microcontroller into Sleep mode and then compares the PIC current consumption during Sleep mode and the normal operation mode.
Sleep and Wake PIC microcontrollers - [Link]
A microcontroller comes with a limited number of input/output lines. If you need an additional 8-bit port in your project without replacing the microcontroller, MCO23008 might be a good choice. It is an I2C compatible port expander and provide eight bidirectional I/O lines for I2C bus. The following tutorial describes the functioning of MCP23008 and its interface with a 8-pin microcontroller like PIC12F683.
Expand the I/O capability of your microcontroller with MCP23008 – [Link]
For a long time, I have been trying to find the cheapest and easiest way to control electronic devices wirelessly using a computer. It can open up a lot of possibilities. For example, you could build a radio controlled relay board, and control it from your computer. You could even control the board with a “small” computer such as an Arduino (or any microcontroller for that matter). If your Arduino has an Ethernet shield, you could use it as a Web server and control your relay board from anywhere in the world (as long as you have access to the Internet of course). There are many things that you could do without creating a mess with wires. I am mainly interested in this because I need a computer controlled wireless robot. A little background -
Computer Controlled Wireless Robot Build – [Link]
Turn off the Heater behind Me… [via]
Ed Nauman had a bad habit of leaving his workshop at night without turning off the heater. His wife would get up in the morning and find – to her consternation – the workshop was plenty toasty. In the interest of keeping peace in his household, Ed decided to create a gadget that would save the energy spent through forgetfulness. He knew he could buy an off-the-shelf solution, but as he says, “Where’s the fun in that?” Instead, Ed turned to the world of thermostats and microcontrollers.
Turn off the Heater behind Me – [Link]
It is a very simple data logger project based on PIC12F683 microcontroller. The microcontroller reads temperature values from a temperature sensor on a regular interval basis and stores them into its internal EEPROM memory. The recorded temperatures can be later transferred to a PC through serial interface. I originally published this project on electronics-lab.com last summer. I thought this could be a very good learning project for beginners, and so I am posting it here for Embedded Lab’s readers too.
A Beginner’s data logger project using PIC12F683 microcontroller – [Link]
Microchip has announced an expansion of its 8-bit segmented LCD microcontroller (MCU) family with five new devices—the PIC16LF1902/3/4/6/7 (PIC16LF190X) MCUs. The PIC16LF190X family supports many general-purpose applications and enables the implementation of LCD into low-power and cost-sensitive designs, such as security tokens, smart cards, medical devices, home appliances, key fobs or any application involving a segmented LCD. [via]
Microchip introduces PIC16LF190X 8-bit PIC® MCUs with integrated LCD control – [Link]