This relatively simple circuit uses a 6-V DC supply with a PWM current-source configuration to provide efficient, adjustable dimming of a white LED over a wide range, needed to accommodate the unique lighting needs of an optical microscope over its magnification range from 40× to 1000×. by James Campbell
When the built-in incandescent light source of my venerable Olympus microscope failed after many years of use, I decided to design a reliable modern replacement. A 1-W white LED (SEOUL X42182, 350 mA max, Vf = 3.25 V) was the obvious choice to provide high brightness and full-spectrum light without the heat of incandescent or xenon arc lamps. The microscope lamp brightness needs to be adjustable, however, to accommodate the different objective lenses, which offer magnifications from 40× to 1000×.
Current Source For LED Microscope Illuminator Provides Full-Spectrum Light - [Link]
Will O’Brien developed this project allowing him to remotely start his car via an SMS sent to a jailbroken iPhone. The additional hardware involved is an Arduino, iPhone breakout board such as the PodBreakout Mini, 4x 10k resistors, 1x TIP120 and a 5 volt switching supply cell charger.
All the details, including source code and schematic are available on Will’s Biobug website
DIY iPhone remote automotive ignition - [Link]
Nothinglabs has posted their circuit for a simple reversible motor control for use with the Arduino and other MCUs. The circuit uses two TIP120 Darlington Transistors, two 220 ohm resistors and a 12 volt DPDT relay, parts easily obtainable at any Radio Shack. This design supports PWM for variable speed control, handles loads up to 5 amps, and is controlled using just two MCU pins for “enable” and “direction”.
Reversible motor control for Arduino and other MCUs - [Link]
Up until now, we have talked about working with a lot of low-power devices. Sensors, LEDs, ICs, and the like are all capable of being powered directly from your Arduino, but as many awesome 5 and 3.3v components as there are, eventually you will find yourself holding a 12v solenoid, motor, or light and wondering “How the heck am I supposed to control this from my Arduino?” Well today we are going to talk about doing just that from a magical device know as a transistor, specifically the TIP120 Darlington Transistor.
Simplified Motor Control Using A TIP120 – [Link]
Aki writes:The electric circuit board for controlling stepper motors came out after figuring out all the specifications of the components. Some sketches were necessary to done. Then Auto-Cad was a great tool for drawing the wires and locate the components. Mainly my circuit is similar than shown in Mel’s page. I didn’t use opto-isolators and couldn’t find TIP120 from a local electric dealer, so I used TIP122 transistors. I also placed the small hand-pad diodes on the board instead of installing them inside of the hand-pad. After soldering work and changing the InverterOutPut (!) to 1 the board started to work. [via]
Stepper Motor Circuit Boards - [Link]