An important circuit to protect:

1- Protect from over and low voltage that damage divice, and can set the high volt by R17 and low volt by R18. to have safe range for your device.

2- Protect from fast volt Fluctuation by using timer feature to protect sensitive devices.

3- Can set circuit using a variable power supply and move R17 until the red LED lights up for highest voltage, and move R18 until the yellow LED lights up to set the low volt, and the circuit will make device off at these values, and play between them.

4- Can set the Time of timer by R7 from seconds to several minutes. To protect from fast voltage fluctuations and have to be a long time for the sensitive devices.

5-To operate the circuit 12 volts to 30 volts 200mA,but the input volt for load is Optional from 1 to 60 volt and output is 1 to 60 volt 15A.

6- The red-yellow- blue led is off and green is on that means: devices are playing.

7- The green-yellow led is off and red-blue is on that means: over volt and devices are off.

6- The green-red led is off and yellow-blue is on that means: low volt and devices are off.

7- The green-yellow-red led is off and blue is on that means: timer start Counting and devices will play when time up.

8- The device can be started directly by pressing a switch to cancel the timer delay time

Note : To cancel the delay time, you need to press the switch each time.

Note:

*The input of the variable voltage and 12v must be from the same power supply(The same GND) 

*Add a small heat sink for 7809 voltage regulator.