[sdiy] [OT] electrolytics specs

[Tim Ressel]

Yo,

--- groovyshaman at snet.net wrote:
> which of the following specs are the most
> important to look for when
> purchasing electrolytics?
> 
> 1) low ESR
Important for switching power supplies

> 2) high temperature
Only if you expect high temperatures

> 3) low leakage current
Important for timing circuits

> 4) low dissipation factor
Important for notch filters

> 5) high permissible ripple current
Bingo!

> 6) low impedance
Kinda the same as low ESR

> 7) long life/high reliability
You get what you pay for

> 8) safety vented
Would be nice for high current supplies

Choose caps that are made for 60Hz power supplies. The
spec sheets usually mention this in the applications
section.

Rule of thumb: use about 2000uF per amp of max output
current. For example: for a 2A supply, figure 4000uF.
Use 2 2200uF or one 4700uF

Working Voltage: I try to get working voltage that is
about twice the expected circuit voltage. For example:
if a 5V supply uses 9V of raw voltage, I'd go for at
least a 16V cap, preferably a 25V. 

I have 20 year old supplies I made using these rules,
and they still work just fine with the original caps.

--TR


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