Programmable Capacitor Kickstarter, Why is this a top project?

[Triode]

https://www.kickstarter.com/projects/raptorbird/programmable-capacitor

There must be something I'm not getting here. Why are so many people backing this device for $29 and it's on the front page for technology? You can get a breadboard and a big compartment box of assorted capacitors for that much.

 

[Ramussons]

That's because most of the "modern" hobby'sts don't know that the Capacitor values are critical only in tuned circuits. Else where, it makes no difference even if one is off by quite a large margin.

Ramesh

 

[ronsimpson]

I have a number of "C boxes", "R boxes", "L box" and some RC boxes. I find them very useful.
The link shows the smallest capacitor of 0.1pF. I find when the capacitor value is below 50pF the stray capacitance causes errors. I think the capacitance of the input connector is close to 1pF. The PCB capacitance is many times that. There are 32 switches, each having capacitance. How can you get 0.1pF? I don't think this product has been tested. My guess is with all the switches open, (0 pf), there will be 30 pF or more.

 

[audioguru]

I rarely used a breadboard due to its intermittent contacts, many wires and rows of contacts that picked up interference and high stray capacitance.

I have made many prototype circuits (most were sold). I always calculated a capacitor value then another value was rarely needed. If I changed my mind about a cutoff frequency, oscillator frequency or timing then I simply desoldered the existing capacitor and changed it.

Maybe this product with many combinations of switched capacitor values might be used by a school kid who does not know how to calculate a capacitor value.

 

[Triode]

I rarely used a breadboard due to its intermittent contacts, many wires and rows of contacts that picked up interference and high stray capacitance.

Yes, in fact when I use a breadboard to build a circuit with an oscillator and it requires small capacitors such as 22pf, I often find that if I put them in it doesn't work well, but if I leave them out it does.

Though that brings up the question of whether there is even a point in the lower values of this device, they'll probably get lost in all those long parallel traces, and possibly the switches themselves.

 

[JimB]

A variation on the old theme of a "Capacitance Box", sometimes when experimenting an adjustable capacitance which is above the range of the usual variable capacitors is usefull.

Though that brings up the question of whether there is even a point in the lower values of this device

Yes anything less than 20 or 30 pf is doubious in something with a physical construction like that, and 0.1pF is just into the realms of fantasy.

JimB

 

[tomizett]

And then you just end up deciding you need 17.83nF, and spend ages looking for one in the catalogues.
Everyone knows the correct value component is the one you've got most of in the junk box!

 

[Triode]

And then you just end up deciding you need 17.83nF, and spend ages looking for one in the catalogues.
Everyone knows the correct value component is the one you've got most of in the junk box!

Haha, very true, I have about 5 lbs of ceramic 104 caps. So unless I'm doing something very touchy it usually gets one of those.