Hello allaboutcircuits members,
I just recently overheated the engine on my car to the point of blowing the head gasket. Being more mechanically inclined then building electrical circuits, i'm asking for help creating a 12 volt automotive engine over heat warning and shut down circuit using a 555 timer with two temperature thresholds. During the first over heat threshold, the circuit will sound a piezo buzzer preferably at 4 Khz and blink an LED. If the warning is not heard over loud music or otherwise and the engine is allowed to over heat a few degrees more to the second threshold, a fail safe shut down circuit will engage, disabling the engine from over heating further.
Instead of utilizing the vehicles engine coolant instrument cluster gauge or ECM/ECU/PCM NTC temperature thermistor, i'd rather use a standalone NTC thermistor attached to a bolt, on the head of the engine, via a ring terminal so it will be universal from one vehicle to the next. This way it will be a foolproof design as some vehicles have the engine coolant thermistors up high and ineffective during low coolant situations, exposing them to air and giving a false low reading.
The shut down circuit may use a 30A SPST mechanical relay with snubber diode, as I believe the circuit and parts list should be as simple as possible so others can easily make it for their own personal use.
Ignition shut down relay:
(NC) 30 & 87A will complete the vehicles primary ignition circuit under normal engine temperatures
(NO) 30 & 87 will disengage the ignition circuit during over heat engine temperatures.
Disclaimer: Shutting down an engine can be dangerous in certain instances and the circuit should be used with caution. Perhaps a switch should be within reach of the driver, applying 12V to 87A of relay when turned on.
I just recently overheated the engine on my car to the point of blowing the head gasket. Being more mechanically inclined then building electrical circuits, i'm asking for help creating a 12 volt automotive engine over heat warning and shut down circuit using a 555 timer with two temperature thresholds. During the first over heat threshold, the circuit will sound a piezo buzzer preferably at 4 Khz and blink an LED. If the warning is not heard over loud music or otherwise and the engine is allowed to over heat a few degrees more to the second threshold, a fail safe shut down circuit will engage, disabling the engine from over heating further.
Instead of utilizing the vehicles engine coolant instrument cluster gauge or ECM/ECU/PCM NTC temperature thermistor, i'd rather use a standalone NTC thermistor attached to a bolt, on the head of the engine, via a ring terminal so it will be universal from one vehicle to the next. This way it will be a foolproof design as some vehicles have the engine coolant thermistors up high and ineffective during low coolant situations, exposing them to air and giving a false low reading.
The shut down circuit may use a 30A SPST mechanical relay with snubber diode, as I believe the circuit and parts list should be as simple as possible so others can easily make it for their own personal use.
Ignition shut down relay:
(NC) 30 & 87A will complete the vehicles primary ignition circuit under normal engine temperatures
(NO) 30 & 87 will disengage the ignition circuit during over heat engine temperatures.
Disclaimer: Shutting down an engine can be dangerous in certain instances and the circuit should be used with caution. Perhaps a switch should be within reach of the driver, applying 12V to 87A of relay when turned on.