This tutorial discusses some general rules of thumb that make it easy to understand and analyze the operation of most opamp circuits. It presents some ideal properties of opamps, and discusses how negative feedback generally causes the input voltage difference to be equal to zero (input voltages are made equal by the action of negative feedback). In other words, the output will do whatever it can to make the input voltages equal. Applying this simple fact makes it easy to analyze most opamp circuits.
Basics of Opamp circuits – a tutorial on how to understand most opamp circuits - [Link]
A while ago I needed some small value resistors as current shunts and I started wondering about the feasibility of using traces as resistors.
There are many theoretical reasons as to why copper traces make bad shunt resistors, but I found surprisingly little practical data.
The traces are (from left to right):
- 20 mil wide, 1221 mil long, should be ~30mOhms
- 6 mil wide, 611 mil long, ~50mOhms
- 12 mil wide 1221 mil long, 50 mOhms
- 6 mil wide 1221 mil long, 100 mOhms
Using traces as resistors - [Link]
A crazy way to convert a 600mil DIP to 300mil. [LPC1114] - [Link]
LED drivers are electrical devices that regulate the power of LEDs. What makes them different from conventional power supplies is their ability to respond to the ever-changing need of LEDs in a circuit by supplying a constant amount of power as electrical properties change with temperature.
The PCA9622 is an I2C-bus controlled 16-bit LED driver optimized for voltage switch dimming and blinking 100 mA Red/Green/Blue/Amber (RGBA) LEDs. Each LED output has its own 8-bit resolution (256 steps) fixed frequency individual PWM controller that operates at 97 kHz with a duty cycle that is adjustable from 0 % to 99.6 % to allow the LED to be set to a specific brightness value. An additional 8-bit resolution (256 steps) group PWM controller has a fixed frequency of 190 Hz and an adjustable frequency between 24 Hz to once every 10.73 seconds with a duty cycle that is adjustable from 0 % to 99.6 % that is used to either dim or blink all LEDs with the same value.
These LED drivers are based on system-centric, mixed-signal LED driver technology for backlighting and solid-state lighting (SSL) applications. This broad-based and rapidly growing market includes LCD TVs, PC monitors, specialty panels (industrial, military, medical, avionics, etc.) and general illumination for the commercial, residential, industrial and government market segments. LED drivers utilize a proprietary and patented combination of analog and digital circuit techniques and power control schemes.
- PCA9622 I2C-bus controlled 16-bit LED driver
- 2C-BUS/SMBus MASTER
- Resistor 10kΩ ( 27 units)
- LED (88 units)
- Voltage Source 40Vdc
- Voltage Source 5Vdc
I2C Bus Controlled LED Drivers for backlighting and SSL applications – [Link]
The TPS7H1x01 is a low dropout (LDO) linear regulator that uses a PMOS pass element configuration. It operates under wide range of input voltage, from 1.5 V to 7V while offering excellent PSRR. The TPS7H1x01 features a precise and programmable fold back current limit implementation with a very wide adjustment range
- Current share/parallel operation to provide higher output current
- Wide VIN range: 1.5 V – 7 V
- Applications: Power management – LDO, RF components VCOs, receiver, ADCs amplifiers, high voltage, high PSRR, low noise and clean analog supply requirement applications
TPS7H1101 – 1.5 -7V Input, 3 Amp, Ultra Low Dropout Regulator - [Link]
The LTC3128 is a high efficiency, input current-limited buck-boost supercapacitor charger with active charge balancing for 1 or 2 series supercapacitors. The LTC3128 features an average input current limit that can be programmed up to 3A with +/-2% accuracy, preventing power source overload while minimizing capacitor recharge time. Highly efficient active charge balancing eliminates dissipative external ballast resistors, ensuring balanced operation and charging with mismatched capacitors, and less frequent recharge cycles. A programmable maximum capacitor voltage clamp actively monitors and enforces the voltage across each capacitor in the series stack, ensuring reliable operation as capacitors age and develop mismatched capacities. The low noise buck-boost topology allows the output supercapacitor to be charged whether above or below the input.
LTC3128 – 3A Monolithic Buck-Boost Supercapacitor Charger and Balancer - [Link]
Julian Ilett show us how to program the Pro Mini Arduino using a simple USB to Serial adapter. Three USB to Serial adapter are tested here. He writes:
Here I attempt to use 3 different USB to Serial modules to program a clone Arduino Pro Mini. The chips are the FTDI FT232RL, the Silicon Labs CP2102 and the Prolific Technologies PL2032HX.
Arduino USB-to-Serial Tutorial – Programming the Pro Mini - [Link]
Super cheap way to make a dummy load for testing high power PSUs.
Dummy load in a bucket - [Link]
Weiss build a Stepper motor controller to make it easy to test out variety of stepper motors. Just connect power and the motor and you are ready to go. He writes:
The idea is to make a quick and simple tool to test stepper motors and mechanical assemblies such as stepper driven gearboxes and linear activators.
Just hook up whatever power supply (between 8 and 24V, AC or DC) you have lying around to the screw terminals or the barrel jack connector and whatever stepper driven device you have to the motor out pin header or screw terminal and you are ready to go.
Easy Stepper Motor Controller - [Link]
This is a great credit card sized business card and gaming console based on Arduino.
The primary trick of this design is having milled cutouts made for surface mount components to be press fit into, using the circuit board as a kind of frame. Components selected have a thickness near that of the circuit board (1.6mm). Furthermore, to minimize the board thickness, the Atmega328P is inverted so that the bulk of its height below the surface. The result of equal thickness and recessed installation provides a flush appearance. The primary benefit beyond the aesthetic quality is the device is easily slid from a wallet. The high quality boards and the excellent service from oshpark also makes this build possible.
Arduboy: The Interactive Digital Business Card - [Link]