Making Electronics
To control solenoid valve I used a famus and popular electronic timer NE555. It is extremely easy to build.
It has two potentiometers to control valve opening and closing times. Setting these values allows to obtain any Rate Of Fire.
Also the System has a Full-Auto and Semi-Auto jumper to choose fire type option. The LED diode inform when system is working.

NE555 Timer and other electronics parts for fire control unit.
Parts List:
At first go to the shop to gather some electronic components.
No. | Quantity | Name | Value |
1 | 1 | PCB Board | - |
2 | 1 | Timer NE555 | - |
3 | 1 | LED Diode | - |
4 | 1 | Jumper and PINs | - |
5 | 1 | Transistor | BD233 |
6 | 2 | Diode | IN4007 |
7 | 1 | Capacitor | 2.2uF 50V |
8 | 2 | Potentiometer | 200k |
9 | 1 | Resistor | 4.7k Ohm |
10 | 1 | Resistor | 50M Ohm |
11 | 1 | Resistor | 2k Ohm |
12 | 2 | Connector | - |

NE555 Timer - Assembled unit and ready to work.

NE555 Calculator: click here to download | Go to Program Website

Control Unit Box - external view.

Control Unit Box - inside view.
Second Step - Shooting Mechanism
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