What capacitors to purchase?

[Hellmut1956]

Hi friends, due to health problems it has taken a very long time but finally I am approaching the point in time were i can start to work in my new electronics lab. I do plan to work first using the Raspberry Pi and have purchased the book from Yury Magda: RaspBerry Pi Measurement Electronics: hardware and software. I have purchased the complete E-series of resistances to ensure to have them readily available, but i am not sure what capacitars i should purchase to have in my inventory. I do have the decoupling capacitor for ICs, I have the capacitors for controlling the electronic noise of motors and those required in ucontroller circuits to connect the cristal. The experiments in the book such new areas like Op-Amps, DACs, diverse sensors and so on, So I would like to purchase a variety of capacitors that I might encounter a need for as I go through the experiments in the book and with own circuitry.

I am aware that there are electrolitic capacitors were the polarity plays a major role, I am just asking what would be equivalent and worthwhile to put in inventory as i have done with the resistors. Shipping otherwise becomes a major cost!

 

[AnalogKid]

If you are talking about buying a "complete" set of capacitor values like you did for resistors, many distributors have kits that are less expensive than a long list of individual part numbers. If that isn;t an option, here are my suggestions.

For values, follow the series 1, 2.2, 3.3, 4.7, 10, etc. This covers two different equi-spaced logarithmic scales, two values per decade (1, 3.16, 10, 31.6, etc.) and three values per decade (1, 2, 5, 10, 20, 50, etc.) with industry standard values. Buy all values between 1 nF and 2.2 uF. For general purpose work, ceramic or metalized film construction, rated at 50 V and 10%, should cover your needs. Panasonic has a line of metalized film, 5% parts that is excellent, but about twice as much as ceramic.

For smaller values for high frequency stuff, ceramics work well. Mylar works better, but costs more. I think you can drop a few values for general purpose work. In pF: 10, 22, 47, 100, 220, 470.

For larger values, go to electrolytics. Aluminum radials are the standard for general purpose work. I'd start at 1 uFand follow the series up to 220 uF or 470 uF. Above that, the cost per part gets expensive, and it might be better to wait until you have a specific need (like a 4700 uF power supply filter) before investing in fat parts that don't always fit into small parts drawers. Again, 50 V is a good starting value because it can handle 24 V and +/- 15 V applications.

ak

 

[Hellmut1956]

Thanks a lot AnalogKid