The content addresses an easy overload cut off circuit for protecting heavy mains managed machines for instance a lathe machine.
I have at present talked about one effortless overload protector circuit design in one of my prior content, the same works extremely well for the suggested lathe machine overload cut off application.
Making reference to the circuit diagram below, you can easliy discover the following main levels in it:
An opto coupler level powered by a bridge rectifier
and a latching relay circuit stage together with the above opto coupler level.
The AC mains is supplied at the suggested left side input, that may be passed on to the load via a load sensing resistor R1 and the linked cut off relay's N/C contacts, N/C stands for generally closed, indicating the connections are associated across this point while the relay is in a deactivated position.
R1 is positively measured such that a potential difference satisfactory enough to activate the opto LED produces across it the moment an overload going over the harmful zone is achieved.
The overload cut off process is carried out in the following manner:
For assuming that the load is within the the standard selection of consumption, the voltage across R1 continues low, retaining the opto LED disabled.
In spite of this in case of a short circuit or an overload at the output, which is usually in a lathe machine for the suggested design, the voltage across R1 shoots and results in being suitably high to be able to activate the opto LED promptly.
The opto LED subsequently brightens the related LDR sealed inside the light proof enclosure producing its resistance to fall drastically.
This drop in the the LDR voltage enables a biasing current to the base of R1 which together with T2 quickly flips into a latching mode activating the relay.
The relay links reply this and offer the essential changeover cutting off the AC line to the load or the lathe machine.
The circuit continues latched and frozen until the power to the circuit is shut OFF and activated resetting the relay in its initial form. Conversely the proven push button are often pressed for the same.
The green LED shows the latched mode of the overload protector circuit along with ensures a power off to the output load.
The opto coupler is a homemade device, the development particulars could also be researched in this article:
Employing an LED/LDR combination for the opto coupler appears significantly trustworthy in its procedures, on the other hand a normal LED/transistor opto (for instance a 4n35 etc) could also be tested instead, and might possibly perform as reliably, it might be a matter of some experimentation.
R1 could also be measured making use of the following formula:
R1 = LED forward voltage / overload current (in amps)
P1 s for adjusting the sensitivity of the circuit.