Making Your Own Cheap Power Supply

Old desktop computers are thrown into the trash by the thousands. You can salvage a power supply from one, or buy new at a computer store for under $20. Then follow these instructions to convert to a very respectable high power benchtop supply. Follow all safety precautions! Detailed information and how-to: Another tutorial: Continue Reading →

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 →

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 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 →

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