Meter clock: keeping “current” time. Read more about the clock:
I’ve seen a few meter clocks in my travels of the web, and I love the idea. A few days ago, I decided that I must have one of my own. Such began the “How to do it” pondering cycle. I had seen builds where the face plate of the meter is replaced. This works, but I wanted to try and find a way to do it without modifying the meter, if possible. After some more ponderation, I came up with what I think is a serviceable idea.
I came across this style of milliamp meter on Amazon. They’re not quite 0-60 mA, but the 0-100 mA (a 0-20mA meter for the hours) is close enough. And they were cheap. So yay.
Part of my requirements were that the clock run off of an Arduino Pro Mini I had lying around, and with minimal additional parts. In order to drive the meters with some degree of precision, I would use the PWM pins to vary the effective voltage across a resistor in series with the meter. This would, by the grace of Ohm’s Law, induce a current that, based on the PWM duty cycle, would be scaled in such a way as to move the needle on the meter to the corresponding hour, minute, or second.
One minor issue came up in the form of the max current the GPIO pins on the ATMega328 chip can source/sink. The pins can source/sink a maximum of 40mA, a bit far from the 60mA needed for the minutes and seconds meters. Enter the transistor.
Using a simple NPN transistor switch circuit, I was able to provide the current for the minute and second meters from the 5V supply. The PWM signals switch the respective transistors on and off, effectively varying the voltage across the resistors in series with the meters.
The resistor between 5V and the meter is actually 2 1/4 watt 100 Ohm resistors in parallel for an effective resistance of 50 Ohms. The two in parallel was necessary as 5V x 0.06A = 0.3W (more than 0.25 that a single 1/4W resistor can handle safely).
Meter clock: keeping “current” time - [Link]
Embedded modules may surprise you by their contribution and an overall costs savings.
As we know „embedded module“ is a quite wide term and it can represent a powerful microcomputer with OS, but it can also be a significantly simpler module with a microcontroller and peripherals, still able to add considerable functionality to a target device.
Typical representatives of useful modules, which add a lot – without big costs are so called quick start modules from company Embedded Artists. Their contribution is in a ready-made „tuned up“ PCB containing for example in case of module LPC4088 QuickStart Board (EA-QSB-016) the microcontroller itself (Cortex- M4), memory, display controller and many interfaces like Ethernet, USB, UART, SPI, CAN, PWM, Analog In/Out, I2C, XBee compatible connector and other.
Especially at low and mid-volume production batches their contribution is mainly in the fact, that it is a really proven solution with a guaranteed operating temperatures range, proper ESD protection and mainly – supported by a wide scale of development tools (free). In case of solving of problems, it´s still possible to contact customer support of company and a lot of hints for successful usage, source codes and libraries can be found directly on the producer´s website.
Try to go easier way - [Link]
Microsoft have released a non-commercial version of Windows based on Windows 8.1 to run on the Intel Galileo development board. A spokesperson for Microsoft said “This preview Windows image is another opportunity for makers and developers to create, generate new ideas and provide feedback to help Microsoft continue making Windows even better on this class of device”.
The board and OS are part of the Windows Developer Program for the IoT (Internet of Things) which Microsoft hopes will encourage developers of Internet-connected devices to experiment with Windows platforms. The Galileo kits include the standard Arduino Wiring API and a subset of the Win32 API. At the moment Linux is the OS of choice among makers and for the next generation of devices but Microsoft hopes to break that dominance. Intel released an update to the original Galileo Gen 1 board earlier this month which features an improved control of its PWM (Pulse Width Modulated) output signals to make the board better suited for the management of 3D printers and robotic applications. Galileo Gen 2 can also be powered from the Ethernet port which the earlier Gen 1 version did not allow.
Galileo now runs Windows - [Link]
Integrated with the homemade low-pass filter, this Arduino-based simple WAV player is to send out PWM signal generated by UNO,
then through the low-pass filter and make the PCM data stored in the flash of UNO into sounds. Basically, the player cannot be regarded
as a pure WAV playback, because by extracting the data from the WAV file and storing it in an array format in UNO, this tutorial is for reference.
You can make SD card based WAV player by referring to this idea.
How to make a simple wav player by using Arduino - [Link]
herpderp shares his waveform generator:
Here is my last project, a tiny waveform generator based on my previous project and some components:
– An AD9834 (DDS chip with sinus/triangle output)
– 2 x AD5310 (10bit DAC: one for the Vpp control, another one the offset control)
– 3 x LM7171 (Fast OPA)
– 3 x LT1616 (switching regulator: +5V, +7V, -7V)
This waveform generator is directly powered by a standard 12V jack and is capable of outputting a 10Vpp signal at 1MHz (between -5V and +5V, sinus waveform, no load). Above 1MHz, the output starts fading, reaching only 9Vpp at 4MHz (maximal frequency). Frequency, amplitude and offset are digitally controlled through the smart TFT.
Three “basic” waveforms are provided: sinus and triangle, coming from the DDS chip (0.1Hz to 4MHz, 0.1Hz step), and PWM coming from the microcontroller (0.1Hz to 1MHz, variable steps).
Tiny waveform generator - [Link]
An application note from Texas Instruments, white LED driver with digital and PWM brightness control (PDF!):
With a 40-V rated integrated switch FET, the TPS61160/1 is a boost converter that drives LEDs in series. The boost converter runs at 600kHz fixed switching frequency to reduce output ripple, improve conversion efficiency, and allows for the use of small external components.
The default white LED current is set with the external sensor resistor Rset, and the feedback voltage is regulated to 200mV, as shown in the typical application. During the operation, the LED current can be controlled using the 1-wire digital interface ( Easyscale™ protocol) through the CTRL pin.
App note: White LED driver with digital and PWM brightness control - [Link]
Ondrej Karas of DoItWireless writes:
This is simple illustration how to build easy PWM LED control with IQRF TR module and a few other components.
This device is powered from 12V/6A DC power supply and can power up to 5m of LED strip. This device can be controlled via RF, buttons or potentiometer. RF controlling is compatible with remote control device RC-04 with low battery signalizing – fast 3 time LED blinking.
RF PWM LED control - [Link]
An SMPS application using PIC16F785 from Microchip. [via]
In this application note, we will examine a typical buck topology intelligent SMPS design using the PIC16F785.
The design presented here shows an alternative single-chip approach to adding intelligence to SMPS designs. The basic design is really unchanged. There are current and voltage feedback loops, a counter-based PWM is used to generate the reference voltage to the voltage loop, and the microcontroller uses the reference voltage to modify the operation of the system in response to conditions sensed through the ADC.
App note: Switching power supply design with the PIC16F785 - [Link]
praveen @ circuitstoday.com writes:
PWM or pulse width modulation is a very common method used for controlling the power across devices like motor, light etc. In PWM method the power across the load is controlled by varying the duty cycle of the drive signal. More the duty cycle more power is delivered across the load and less the duty cycle, less power is delivered across the load. A hex keypad is used for controlling the speed. The speed can be varied in seven steps using the hex keypad. Arduino UNO is the type os arduino development board used in this circuit. The circuit diagram of the PWM motor speed control using arduino is shown in the figure below.
PWM motor speed control using Arduino - [Link]
Nich Fugalfrom @ Makeatronics is working on a BLDC motor controller.
Icall it a smart BLDC commutator. In a nutshell it’s a dedicated atmega328 that monitors the hall effect sensors on a brushless DC motor and takes care of the commutating and driver circuitry.
It’s smart because it has the ability to extract and keep track of motor position while monitoring the hall sensors. There’s also an option to plug in a quadrature encoder for higher resolution. The position can be sampled via a sample and hold input and communicated to a host controller via SPI.
I designed it to be an easy to use black box for interfacing with BLDC motors. All the host controller has to do is feed it direction (high/low) and PWM and the rest is done for you.
BLDC motor control using Atmega328 - [Link]