5V SPDT Relay

The SparkFun 5V SPDT relay is typical of its kind. Although its coil needs only 5V to switch on, it needs more current than the Arduino can supply - although in practice it does work connected directly. Its coil resistance is 57 ohms, therefore it needs 88mA @ 5V to turn on consistently (i =... Continue Reading →

Stepper motor animation and half-stepping

The above animations show a stepper operating in normal full step mode. If you need more precision, here is a technique to double the resolution by "half-stepping": http://www.physics.ubc.ca/~kotlicki/Physics_319/MOTORSTEPTUT.html Stepper Motor library alteration for half-stepping: http://code.google.com/p/arduino/issues/detail?id=139

Voltage Divider circuit

  A voltage divider (also known as a potential divider) is a simple circuit that produces an output voltage (Vout) that is a fraction of its input/supply voltage (Vin or Vs).  Basically voltage is divided according to the ratio of the resistors. It has many uses but a common one is converting a variable resistor like a photocell or... Continue Reading →

Breadboard internal connections

Breadboard holes are sized for nice press-fit with 22ga solid wire (the kind we use for most stuff). The rows of holes are connected to each other inside, separated by a center channel. This allows for insertion of IC chips whose pins need to be isolated. The green highlighting represents holes connected to each other.... Continue Reading →

Scrollables

Scrollables is a series of multi-scroll devices, an exploration of possible applications for a paper-based tangible interface. As paper as a medium is more and more threatened by the introduction of portable multi-touch screens and e-readers, the project aims at bringing back the tactile relationship with this material as a way to interact with the... Continue Reading →

Transistor circuit

Here's how to use a TIP120 transistor to control higher voltage or higher current loads. This circuit will also work for an IRF520 MOSFET. The load could be a motor, or an ultrabright LED, or 50 LEDs you want to switch on with one pin, or anything higher voltage DC. Maximum 60V, 5A (8A if pulsed).... Continue Reading →

Relay circuit

Notice that in many relay circuits you will see a transistor used in addition to the relay. This is to ensure enough current is coming through to activate the relay. Often the Arduino can do this directly, but some relays require more current. More examples: http://www.instructables.com/id/Connecting_a_12V_Relay_to_Arduino/ http://www.glacialwanderer.com/hobbyrobotics/?p=9 SparkFun Controllable Power Outlet tutorial http://blog.makezine.com/archive/2009/02/connecting_a_relay_to_arduino.html

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