Prototype the Easy Way with a Programmable Capacitor
Randy Boulter posted on November 19, 2013 |

Access over 4 billion possible capacitor values through this one simple interface.

It happens all the time, you’re working on a project or prototype and you cannot find the right value capacitor. The project comes to a halt, frustration builds up, and you’re reduced to hours of infinite math trying to combine the capacitors you do have. To make sure this never happened again, Rakshak Talwar of created his own programmable capacitor.

I spoke with Rakshak about his product recently and he confirmed that it grew out of his own frustration in finding capacitor values. Steering far from the cumbersome and expensive design of decade boxes (also known as capacitor substitution boxes), Rakshak decided to produce a simple board with multiple capacitors. You turn on the capacitors you want to use and their values add up, allowing you to make any value capacitor with just a few flipped switches. It is a simple and elegant solution to a very common problem.

To use the Programmable Capacitor, you simply plug jumper wires into your circuit where the capacitor goes and then set the switches for the right value. If, for example, you are working with a filter circuit and do not know the exact value you need, you can quickly try different values until you find the right one. The instructions are even printed on the back of the circuit board.

In terms of the design process, Rakshak said that “deciding on the capacitor values to place on the board was the biggest challenge;” though he also struggled with “laying out the PCB to eliminate any stray capacitance which could affect the smaller values.” Rakshak also opted for dip switches, rather than the jumpers most of his colleagues recommended, favoring the dip switches’ more robust design. “It is important,” he stated, “to make the product robust enough to withstand the abuse it will receive in schools and universities.”

The target markets for the Programmable Capacitor are hobbyists, project enthusiasts, and schools and universities. I can see where there would be a market among engineers and technicians too, as many of them prototype circuits and have the same problem with capacitors.

Raptorbird currently has a Kickstarter campaign for the Programmable Capacitor. To date, the campaign has raised over $6,000 on its original goal of $3,000.

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