Physical Computing & Interaction Design
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 →
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
How to wire up the larger stepper motor from SparkFun using an H-Bridge (SN754410): (Images adapted from https://www.arduino.cc/en/Reference/StepperBipolarCircuit) Note where pin 1 of chip is (marked with dot or U cut-out). This motor requires 12V and up to 330mA of current. Red and Green wires are one coil, and Yellow and Blue the other coil. Motor... Continue Reading →
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 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 →
Most LEDs will burn out if connected to a 9V battery without a resistor. The resistor lowers the amount of current flowing through the LED. To calculate how much resistance is needed, you can assume the average LED takes around 2V and 20mA (if you want to be more precise, look up by color, or... Continue Reading →
http://vimeo.com/38796545 With this noisy chemistry lab, the gamer will create his own jelly with water and a few grams of agar agar powder. After added different color, the mix is then pour in the molds. 10 min later, the jelly shape can then be placed on the game board, and by touching the shape, the... Continue Reading →
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 →
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 →
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
