Time-based positioning for DC motor-operated equipment - has counter recording VCO and motor running time for comparison with memorised demand based on operating time

摘要

A DC motor (100) used for positioning a unit e.g. a vehicle's rear-view mirror runs when a control unit (400) operates its control switch (300). A user input to this unit is simultaneously memorised (800). First movement is in reverse, until engagement with a stop produces a current rise which is established (900,950) as a starting point. Thereafter, a counter (600) records an elapsed time which is compared (700) with the memorised input until, when equal, the control switch is reopened. Accurate positioning is based on the principle that motor speed, and hece distance run, depends upon input voltage. A VCO (510) is therefore provided in the counter feed to compensate in its elapsed-time recording for fluctuations in the DC supply employed. ADVANTAGE - Time-based positioning of motor-controlled equipment avoids use of bulky sensors, and use of VCO in circuit prevents difficulties due to supply, and hence motor speed, fluctuations.