Monitor circuit for direction indicators of vehicle and trailer - tests functioning of all lamps prior to visual energisation and indicates defect at dashboard repeater lamp

摘要

The monitor measures a test current via the resistors (RL, RR) and switches (SL, SR) when either a LH or RH lamp circuit (BLL, BLR) is operated and a difference threshold is used to indicate a defect. The test current is of, e.g. msecs duration in order to avoid visual response of the lamps (BLL, BLR), after which in healthy conditions normal flashing indication ensues for the selected direction. In the event of a defect in the selected circuit the flashing frequency is doubled by the IC (15) with dashboard indication by the lamp (LK). A defect in the non-selected circuit is similarly revealed the first time it is energised. USE/ADVANTAGE - Gives simple and reliable warning of vehicle/trailer indicator circuit fault each time operated. Difference threshold of LH and RH circuits is readily adjustable to allow for lamp tolerances. Comparison is made before visual response occurs.