I'm having difficulty sourcing the correct/safe capacitor for this circuit (despite my research).

I know it should be 0.01uf and is being used in a 120v AC (upto 10amp) circuit. Schematic below. Also attached: Photo of the creator's circuit.

Are typical disk capacitors ok? (ie capacitors @ local store)

schematic circuit image

  • \$\begingroup\$ One thing we can't tell from the schematic or question, at least the original version, is what temperature range will this need to operate over? Will it need to survive more extreme temperatures when not operating? \$\endgroup\$ – DarenW Sep 29 '13 at 1:39
  • \$\begingroup\$ It'll be used indoors so I'd say normal 15-30C. However, since it will be packaged in a box with this circuit and a relay (x8) the box will heat up expectedly. \$\endgroup\$ – joshjingles Sep 29 '13 at 2:07
  • \$\begingroup\$ Thanks for the response DarenW, any other insights affect the decision would be greatly appreciated. take care! \$\endgroup\$ – joshjingles Sep 29 '13 at 2:08

From my review of Practical Electronics for Inventors by Paul Scherz and Simon Monk, I believe that the ceramic disk capacitor will be OK. You might want to adjust the footprint on Eagle so you minimize how much of the leads you expose, as that can introduce parisitic inductive elements.

One other thing I would really like to note is that ceramic disk capacitors generally aren't polarized. However, your Eagle layout shows a polarized capacitor. In addition, the picture looks like an electrolytic capacitor, which I believe may be polarized. If the application really calls for a polarized capacitor, you might want to stick to the original design.

  • \$\begingroup\$ great insight @shabab. When moving the leads closer is there not a concern of arcing? Polarized. check. \$\endgroup\$ – joshjingles Sep 30 '13 at 13:40
  • \$\begingroup\$ @joshjingles I think the arcing concern would be more relevant for electrostatic discharge or for a higher power circuit. I understand your concern and if you can get away without changing the layout, then go for it. \$\endgroup\$ – Shabab Sep 30 '13 at 14:46

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