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Using LM317 Overvoltage Protection

2016-09-14 20:41  
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This article explains the use of the LM317 overvoltage protection circuit. The circuit is simple but effective. For your more thorough grasp of this principle, we suggest that you can know more about some of the important components of the circuit, for example: LM317 , BC108, BC547, BFY51, BC140. This is a voltage regulator, which allows a portable 6 v 12 v supply is derived from a car battery. You can add a 6.2 v Zener diode and a lead to warn you when the input supply overvoltage. If you can find a relay, and from 6.2 v to 12 v, until you can be connected in such a way that, if more than voltage occurs, then the relay will automatically cut off the output to prevent damage to any connected device.
Such a relay will be very hard to find, so I designed this, it is a simple two transistor circuit will turn off the output voltage should be raised higher than the 6.2 v (this can be achieved by selecting a different value to change the zener diode).
Components as follows:
ZD1 = 3 d 6.2 v Zener diode (you can change it to any value, the circuit will turn off the output if the input voltage is higher than the value of improving the zener diode)
R1 = 1 k resistor (this can be any rated power, which carry a very small power)
R2 = 1 k resistor (this can be any rated power, which carry a very small power)
T1 = low power NPN transistor (BC108 or BC547 can)
T2 = NPN type transistor transistor capable of switching equipment operation (BFY51 or BC140 can switch 1 amps, which is the maximum voltage regulator circuit can handle)
Double check the polarity of the device is easy to blow up the components that you are driving if you reverse polarity. Similarly, if you want to increase the power output of the voltage regulator circuit amperage than 1 LM317 's then connected in parallel, we must ensure that this circuit transistor T2 is high enough rating if you do so. 

LM317 with Overvoltage


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