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Developing Noise Free Pulses For Contacts Disclosure Number: IPCOM000097050D
Original Publication Date: 1962-Apr-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 25K

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Masterson, RJ: AUTHOR


The circuit eliminates contact bounce originating in mechanical switching.

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Developing Noise Free Pulses For Contacts

The circuit eliminates contact bounce originating in mechanical switching.

The circuit is shunted across the contacts. It comprises a pair of alternatively conductive transistors in a feedback arrangement, essentially a monostable multivibrator. The transistors are capacitively coupled. The circuit time constant is such that the output is unaffected throughout the period of the contact bounce. The circuit is reliable, can be made adjustable for various periods of contact bounce, permits variations in driving capabilities, and is conservative of standby power.

T1 is normally biased off and T2 is normally biased on. When the contacts close, the collector of T1, the output and capacitor C1 are all grounded. The charge on C1 causes T2 to cut off and the collector of T2 falls. Feedback through resistor R1 causes T1 to go into conduction. This holds the output at ground regardless of contact bounce for a period of time determined by the time constant of R2 and C1. R2 is adjusted to cover the interval of time in which the contact is bouncing. When the contact starts to open, any intermittency causes the action to take place, effectively eliminating spurious pulses from the output.


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