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Pachinko7 said:Thank you. So I guess I will have to find the real thing ... :roll:
Well, I am building the theremin project that appeared on EPE, October 2004, page 706. It should be cool... I am just trying to gather as many components as possible and start, I already prepared the PCB...Nigel Goodwin said:Pachinko7 said:Thank you. So I guess I will have to find the real thing ... :roll:
It depends on what it's used for, you still haven't mentioned that!.
Pachinko7 said:Well, I am building the theremin project that appeared on EPE, October 2004, page 706. It should be cool... I am just trying to gather as many components as possible and start, I already prepared the PCB...Nigel Goodwin said:Pachinko7 said:Thank you. So I guess I will have to find the real thing ... :roll:
It depends on what it's used for, you still haven't mentioned that!.
I found mica film capacitor of that value on Digi-Key catalogue. I does not mention anything about silver, though. (Part # 338-1017-ND). Is that the right kind of capacitor ?Nigel Goodwin said:Pachinko7 said:Well, I am building the theremin project that appeared on EPE, October 2004, page 706. It should be cool... I am just trying to gather as many components as possible and start, I already prepared the PCB...Nigel Goodwin said:Pachinko7 said:Thank you. So I guess I will have to find the real thing ... :roll:
It depends on what it's used for, you still haven't mentioned that!.
If you can find a silver-mica capacitor of the right value, they are even better than polystyrene.
Thank you very much for this information. It makes sense to me that the characteristics of the silver-mica vary widely even for caps of the same batch, since the dielectric mica is a natural mineral, and is not produced under carefully controled conditions, like the man-made polymers (polystyrene, polyester, etc.). It is very likely that small impurities or variations in composition in the mica, even in the same specimen, will change its characteristics.TheOne said:If your cap will be used in an oscillator, here are some facts to consider.
(This may not be critical to your application, but it is good to know)
Up to about 10MHz it is often practical to use polystyrene caps. They have a slight -ve temperature coefficient making them ideal to use with magnetic cores with a +ve coefficient.
Silver-mica can also be used but their individual drift characteristic may vary from -ve, zero or +ve (even for caps from the same batch!). The only way to grade them will be to monitor the capacitance with a cap meter for change in value over say a 1 hour period in a temperature chamber when the temperature is varied from about 50-100 deg F.
Once graded they make excellent capacitors for use in oscillators because of their high Q like polystyrene.
Pachinko7 said:Why is the temperature coeficient called ve ?