SparkFun: COM-08357

Description: This is a handy little device that can save your system from smoking. A resettable fuse (also known as a PTC) is a resistor that has very unique properties.

For this model, if your circuit tries to draw more than 250mA of current (if you have a bad short for instance) the PTC would ‘trip’ (by heating up). The increased resistance (trip state) would break the circuit and allow only a small leakage current.

The leakage current may still be enough to hurt some electronics but it’s much less than the 3A that the short may have allowed. Removing the short, the PTC ‘resets’ and allows current up to 250mA to flow again. It’s a resettable fuse that protects your system! Good for use on battery powered devices that need to protect again high-current accidental discharges.

The thermal pictures to the right do a great job of showing what happens when the PTC is tripped. The first thermal picture shows a voltage regulating circuit in its normal state. In the second picture the circuit is shorted, notice how hot the PTC gets (213 °F!) as it limits the amount of damaging current going through the circuit. Major thanks to Joshua Weaver for the great thermal shots!

Don Luc

SparkFun: DEV-09709

Description: This is a small prototyping shield for the Arduino Pro Mini. If your project requires just a little bit more space for your external circuitry, this might be a perfect addition. 38 unconnected PTHs are provided for your prototyping needs.

The shield fits the small form factor of the Arduino Pro Mini – connecting to the ‘top’ four pins on each side of the Mini (‘GND’-‘TXO’ & ‘VCC’-‘RAW’). There are small buses for VCC, GND and RAW. In addition to the power buses, the serial pins are also broken out on the shield. The analog and digital pins are not broken out on the shield.

Features:

• VCC, RAW and GND buses
• Serial (RXI & TXO) pins broken out to small buses
• Works with both 5V and 3.3V Pro Mini versions
• Upholds the Pro Mini’s small form factor
• 38 unconnected PTHs for prototyping

Don Luc

SparkFun: PRT-08619

Description: An empty canvas for electrical enthusiasts! Designed to fit the SFE project enclosures this project board gives you 8x10cm (3.15×3.94″) of building space for through-hole components with 2.54mm (100mil) spaced holes. This is not your normal perf board! This board is much higher quality with plated-through holes and annular rings that will not lift off the PCB under normal soldering conditions.

The marsupial naming convention is what happens when you let Engineers into a Marketing meeting. They looked so happy, we just couldn’t tell them no. Wombat is the board with nothing but PTH prototyping pads.

Dimensions: 8x10cm (3.15×3.94″)

Don Luc