Solenoid Current Dip Timing Circuit
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
Performance of a solenoid and its associated hardware is determined by monitoring the solenoid's current vs. time waveform. The purpose of the circuit is to convert the solenoid's DC current vs. time waveform into a pulsed digital signal which can be analyzed by a microcomputer. Prior to energizing solenoid L1, capacitor C1 is charged to +5V through R2. The voltage on the positive input to IC 1 is ground. The voltage on the negative input to IC 1 is -.050 V, as determined by R4 and R5. The voltage at point "B" is +5 V. When L1 is energized, by turning on T1, C1 is clamped to .9 V. This forces the positive input of IC 1 to -.7 V due to the clamping effect of D2 which provides fast recovery. The voltage at point "B" goes to ground. C1 now discharges toward ground through R3.