Programmable capacitor | Hacker News Reader

Programmable capacitor

kickstarter.com

13 pointsanigbrowl12 comments

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Gerry Sweeney has been selling something like this for ages now:

https://www.tindie.com/products/gerrysweeney/five-decade-pro...

I've got his programmable resistor, and its quite handy:

https://www.tindie.com/products/gerrysweeney/seven-decade-pr...

A $25 assortment of capacitors/capacitor goodie bags from ebay or your favourite supplier would be far more useful.

There really is no substitute to building up a stock of parts for prototying where the parts can be part of the completed work.

Interesting idea. I'd be worried that the stray capacitance from the wires and PCB traces would make the total capacitance much higher than intended towards the lower end of the range though.

Programmable caps/resistors are nothing new. I'd be more interested if he had a very high level of polish that would justify the cost of something I could make myself. Either that, or he could better target the Arduino/electronics beginner crowd.

Yes, these have been around as resistance / capacitance / inductance "decade boxes" for at least a century, for example: http://nistdigitalarchives.contentdm.oclc.org/cdm/singleitem... http://www.mouser.com/Test-Measurement/Decade-Boxes/_/N-7uql...

But if the guy can kickstart an inexpensive one for hobbyist use, that's cool.

I can understand why can be useful for newbies in DIY electronics, but I don't understand why need 3000$ for something can be draw in Kicad and put free on Internet.

Because he's not offering a schematic, he is offering a finished board. Have you ever had a PCB fabbed? Huge up-front cost, and the price scales down very quickly with number of units. A $3,000 seed investment lets him produce finished boards at $25/apiece; a $1,000 seed investment (and thus 1/3 of the PCBs) would probably double the cost of the PCB per unit.

A PCB of that size would be about $30 at OSH Park. Hardly a "huge upfront cost".

Sure, but OSH Park is hardly the best way to offer a production board. Yes, he could make one for himself, but is that the goal?

Because Kickstarter.

It even has a resolution of 0.1pF! A pair of these would be fantastic for fine-tuning crystal loading caps.

There is so much stray capacitance around that whole design, let alone the inductance of the leads etc. It would be totally useless for accuracy at the pF level (maybe 'that's the joke'?)

Less programmable, more like selectable.

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