I wonder what is going on with using that
size(capacitance) capacitor. Since the time constant of an RC network is R times
C, that network would have a time delay 50 times as large as the original
diagram indicates. Using a resistor 50 times as large also would result in
a time delay 2500 times as large. To get the same delay with a
capacitor 50 times as large requires a resistor with only one-fifti-eth of the
resistance. The wattage rating of the resistor might need to be changed also.
The circuit current would be different also.
Herb Crary
Boulder CO
>>> Paul Abendroth <pabendroth dma org> 9/17/2006 5:45:04 PM >>> Rhett T. George wrote: The board I am working on has in locations C104, C104, and C105 50 uF, 50 V caps. The schematic shows 1 uF, 100 V caps at those locations. My question is, "Has anyone come across this discrepancy and resolved it to his/her satisfaction?" As my card failed, I just connected pins (10) to (11), etc. Let me take a cut at this circuit: The cap cause a delay between switch 1A closing (10) and energizing the coil of relay 1A (11) determined mostly by C103 and R 109. They delay uni-junction transistor Q101 from triggering SCR 106 on. The SCR then connects (10) to (11). Larger cap or resistor increases the delay. The circuit may also protect the switches from in-rush current while the contacts are just making. Not as big a deal as avoiding arcing when the switch opens. CR106 and R105 may help this. "Also the 100V caps probably have twice their 'rated' capacity at half the voltage." Not true. Capacity is related to area of the foils connected to the wires, and the thickness and type of dielectric between them. Doesn't vary with applied voltage (much). What is true is that capacitors built for half the voltage could have nearly twice the capacity in the same size package, as the dielectric can be thinner without shorting. Both would store about the same energy at rated voltage if I remember right. _______________________________________________ Elec-trak mailing list Elec-trak cosmos phy tufts edu https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak IMPORTANT WARNING: The information in this message (and the documents attached to it, if any) is confidential and may be legally privileged. It is intended solely for the addressee. Access to this message by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution or any action taken, or omitted to be taken, in reliance on it is prohibited and may be unlawful. If you have received this message in error, please delete all electronic copies of this message (and the documents attached to it, if any), destroy any hard copies you may have created and notify me immediately by replying to this email. Thank you.
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