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Use of Flyback Diode for External Output of Wrist Strap and Shoe Tester Disclosure Number: IPCOM000237969D
Publication Date: 2014-Jul-23
Document File: 2 page(s) / 164K

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The Prior Art Database


For most high-end wrist strap and shoe testers, test results are available at the test result's LED in front of the tester, and also at the EXTERNAL OUTPUT connector. An exemplary wrist strap and shoe tester for electrostatic control uses an open collector output that can connect to a sequencer or relay to open and close an automatic door. This relay consists of a solenoid wire and is an inductive load that can create high voltage spikes when the open collector switch turns on and off. This can severely damage the tester's output. The implementation of a flyback diode at the external output can prevent damages from the high voltage spikes. So it prevents customer feedback due to damages of the external output, and reduces testers returned to the lab for repairing with this symptom.

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Use of a Flyback Diode for External Output of Wrist Strap and Shoe Tester 

For most high‐end wrist strap and shoe testers, test results are available at the test result's LED in front  of the tester, and also at the EXTERNAL OUTPUT connector. An exemplary wrist strap and shoe tester for  electrostatic control uses an open collector output that can connect to a sequencer or relay to open and  close an automatic door. This relay consists of a solenoid wire and is an inductive load that can create  high voltage spikes when the open collector switch turns on and off. This can severely damage the  tester's output. 

The implementation of a flyback diode at the external output can prevent damages from the high  voltage spikes. So it prevents customer feedback due to damages of the external output, and reduces  testers returned to the lab for repairing with this symptom. 


Fig 1. External output of a tester, pins 7&8 are to be used to control external doors 


Fig 2. Internal circuit of a tester at pins 7&8 using an open collector output 



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Fig 3. Existing circuit recommended for external output at pins 7&8 to control relay and automatic door 


Fig 4. A flyback diode is implemented at the solenoid of the relay and allows current flow...