What is There to Know About Resistors?

Resistor: A passive chunk of material that resists the flow of electrical current. A terminal is connected to each end you’re done. What could be simpler?

It turns out it’s not so simple at all. Temperature, capacitance, inductance and other factors all play a part in making the resistor a rather complex component after all. Even its uses in circuits are many, but here we’ll just focus on the different types of fixed-value resistors, how they’re made, and what makes them desirable for different applications.

Let’s start with a simple one, and one of the oldest.

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DIY PCB Fixture Helps You Spread the Paste

(Yeah, we don’t know what that title means either.) But holding your PCBs down in one place and nicely registered while you spread solder paste over them is a problem that needs solving, and [Carsten] did it nicely.

High volume PCB manufacturers have expensive screen printers to do this. The standard hardware hacker solution is to tape some scrap PCBs of the same thickness down to the table to hold the PCBs solidly in place. But if you’re doing a large run, and if you’re already firing up the laser to cut out mylar stencils, you might as well cut out some PCB-holding fixtures to match.

[Carsten]’s blog entry is short on details, but you get the idea just from looking at the picture, right? Adding registration pins to the holder that engage with the stencils could make this a real time-saver as well. As long as you’re lasering the stencil and the holder, there’s nothing stopping you. It’s a simple idea, but a good one, so we thought we’d share. Our only remaining question: what’s a Karate Light?

LIB3 plans to bring contract manufacturing to the masses

LIB3's paste system
LIB3’s paste system

LIB3 is an open source hardware start-up from upstate New York. Thus far, the team has made some interesting products such as the piLED kit. However, they have big dreams for the future. LIB3 plans to become a contract assembly house specifically targeting low volume makers. To do this they have to build their own tools. LIB3’s latest project is a solder paste dispenser for surface mount components. Traditionally solder paste is applied with stencils made of stainless steel. In more recent years laser cut kapton has become a favorite for low volume production.

Both of these systems require a stencil to be made up. LIB3 took a different approach, and modified an old CNC glue dispenser for paste. The team got their hands on an 1991 vintage X/Y glue dispensing system. X/Y systems in this era were big, heavy affairs with powerful motors. LIB3 removed all the control electronics and built their own system from scratch. New features include direct computer control, and a vision system.

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