My car (years before CANbus) has a very basic mechanism for detecting bulb failure that uses a heating element and a bi-metalic strip with electrical contacts, as per this circuit.
The input is +12V on R, output to the bulb is RG. WS is the feed to the bulb failure warning light through a NC pair of contacts, attached to a bi-metalic strip. When you switch the light on, the heat from the coil causes the bi-metalic strip to bend and break the feed to the warning light. When the bulb fails, the coil cools and the contacts reconnect. The advantage of this system is that for a few seconds, while the coil initially heats up, the bulb warning light will be lit to indicate that the warning light itself is OK. The downside is that it is prone to failure, cannot handle high current loads like a headlamp, and not very accurate when multiple bulbs and LEDs are connected to the same circuit.
There must be a way of sensing the current flow electronically to provide a more reliable system. What would I need to build a monitoring system for multiple bulbs, in high power circuits and also for low power LEDs, which includes the ability to perform the warning light check when turned on?
The input is +12V on R, output to the bulb is RG. WS is the feed to the bulb failure warning light through a NC pair of contacts, attached to a bi-metalic strip. When you switch the light on, the heat from the coil causes the bi-metalic strip to bend and break the feed to the warning light. When the bulb fails, the coil cools and the contacts reconnect. The advantage of this system is that for a few seconds, while the coil initially heats up, the bulb warning light will be lit to indicate that the warning light itself is OK. The downside is that it is prone to failure, cannot handle high current loads like a headlamp, and not very accurate when multiple bulbs and LEDs are connected to the same circuit.
There must be a way of sensing the current flow electronically to provide a more reliable system. What would I need to build a monitoring system for multiple bulbs, in high power circuits and also for low power LEDs, which includes the ability to perform the warning light check when turned on?
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