Friends, all we know, that, one of the real threat, while playing with RC ships and boats is MOTOR stalling, means jamming of the motor with many reasons.first one is stranding the propeller on anything from a weed to nets, and jamming brush also can cause stalling. the jamming of the armature,makes ample of heat, as it drops a high degree of Amperage, cause potentialy disastrous results.one of the ever simple damage inflicted by this incident is burning of the ESC we used. a heavy money loss will occur instantly. here i am posting a simple proven circuit, for years, to protect our entire unit.
as we can see here, some simple components are used.here transistor BC77 ,metal case acts as a temperature sensor,as its leakage current differs ,accordance with the temperature it stands.this variation is used for biasing an other transistor,and triggering circuit.BC 108 is used as a buffer amp between the sensor and triggering circuit.AC 128 is used to drive a relay here.we can simply adjust the temperature by adjusting the 470Kilo Ohms potentio meter.we can use any general purpose transistors here, but take care to take only metal case transistors as sensors.
how it helps us..?
Here the answer...when a stalling occur, a great heat will produced on the ESC, and motor itself.so we now theres always will be a safest maximum temperature levels, as we use our crafts in water.we can simply fix the metal cased transistor, on ESC, or motor by a simple aluminium clamp or by a screw.then we can adjust the value of the biasing voltage by reseting the 470 K ohms resistor.
we can set the preset, just above the maximum temperature after running our craft for several minutes.so when a high heat sensed by the sensor it triggers the other.instantly the relay energised. opening the DC voltage line to the ESC circuit. so we can save our ESC and motor simultaneously.
this circuit can be used on any circuit as a thermal protection circuit, or can be used for switching off a oven, closing a door as sun hets up, or switching a fan on when room temperature increases,or can be switch on A/C.
when this circuit shuts off a system, never try to re open throttle again.it must need a thorough inspection for any jamming of the motor, or for any short circuit.for a constant vigil, this circuit need a stabilized power supply. for this we can simply use any voltage regulators ranging from 7805 to 7812 ics.its simple.