Turn-key PCB assembly services in prototype quantities or low-volume to mid-volume production runs

Arduino based programmable load

Programmable electronic loads can be handy in many testing applications. It can be used to test power supplies, batteries or tuning other equipment. Practically speaking building controller based load isn’t that hard. All you need to do is to drive MOSFET at some point. This point can be maintained by reading voltage and current on the load. Jasper have built an Arduino controlled electronic load that can withstand 30V and 5A but max 15W. Transistor Gate is with voltage that is set on MCP4725 I2C DAC. The opamp based circuit takes care of maintaining gate voltage at level so the current would stay at desired level. Current is measured with 0.1ohm current sense resistor. Resistor voltage level is amplified and then fed to microcontroller ADC. Arduino Nano is connected to computer through virtual serial port, so parameters can be read and set through terminal screen. Initial code is freely available, but there can be much more improvements made like pulsed load and different modes of operation. Continue reading

3.3V to 5V level shifter for Raspberry Pi

Raspberry Pi is 3.3V based system. This means that it works with 3.3V powered peripherals. For fast hacking it actually can accept 5V signals without damage, but for more secure designs it needs proper level converter. Stuff4Pi made pretty good level converter board for Raspberry Pi which is bidirectional and covers all GPIO pins. Instead of using fancy chips to do this, he found an interesting NXP application note, where it is explained how using single MOSFET and couple resistor it is easy to make bidirectional level converter from 3.3V to 5V. Generally speaking converter works at different voltages like 1.8V, 2.2V, 2.8V as well. So it may be used as general purpose converter. But main purpose was to attach to Raspberry Pi, because the PCB has a form factor that fitns nicely on Pi board. It also has a secondary header (which now is 5V) at same location, so it could be further used for other prototyping. Level shifter also has a dedicated LED for each line for monitoring status of each GPIO line. LEDs are buffered to avoid… Continue reading

Dot Matrix Clock – The Open Source Display

Recently, the open source becomes increasingly popular, especially among the home hobbyists. Many people regarding the open source as the genuine approach to the design, development and distribution of software, which is offering practically accessibility to software’s source code. Some people even consider open source as one of various possible design approaches. Beside that, others might seem it as a critical strategic element of their operations. Before open source became widely adopted, many developers and producers used a variety of phrases to describe the concept. Today, you’re going to have the chance to build a Dot Matrix Clock, which is related with the open source. For your information, the whole project is costing under $150. Here are the characteristics of the Dot Matrix Clock, which as: 40×16 display with two LEDs per pixel giving 1280 LEDs Constant Current LED sink chips (It is to prevent varying brightness problems with the display) PIC 18F4550 microcontroller running off the PLL on a 16 MHz oscillator giving 12MIPS throughput 41-pin high density board to board connector 4 buttons 8-bit parallel bus with CS,… Continue reading

The Colorful Mechanically Scanned LED Display

Is anyone here a big fan of the propeller clocks? Isn’t the logo that flashed out from the high spinning propeller clock fascinated and mesmerized your heart? So, what do you say? Do you want to build a mechanically scanned LED Display, which is having the same effect as the propeller clock did? Sounds interesting, isn’t it? Well, the PCB is the main part of this project. It contains: The PIC microcontroller, Four HC573 latches, Five ULN2003A 7-fold darlingtons, A power supply stuff, A MOSFET (It is to drive the first motor) Two push buttons (They are for setting the date and time). Beside that, you need to use an LM317 adjustable voltage regulator for LED brightness control. Also, make sure that the main power supply should be at least 12 volts, as the ball bearings don’t always conduct perfectly. What is so unique about the mechanically scanned LED display is it can act like: An analog clock (It displays in seconds, minutes and hours form). A digital clock (It has the time, weekday, date and year form). A 64×32… Continue reading