Injectors Circuit Board Write-Up

Regan’s Injector Circuit Board Write-Up

Component List:
• Positive/Negative Inputs
• Channel One and Two Inputs
• Jumper Wires
• 1 Yellow LED
• 1 Clear LED
• 4x 1KΩ Resistors
• 2x NPN BC547 Small Signal Transistors

Calculations:
 • 2x 1KΩ LED Resistors (R1, R2)
(Vs-V Led)/I
(12-1.8)/0.01=1020Ω
Preferred Values of 1KΩ for R1, R2
• 2x 1KΩ Transistor Resistors (R3, R4)

I decided to use the same resistors as the LED resistors to keep the circuit simple and to ensure that my transistor will not be destroyed over time.


How It Works: First the circuit must be connected; so12V is run into the positive input and a second supply of 5V is needed to be attached to the channel one 5V input. The earths of both supplies are placed upon the negative input. With these connections in place the yellow (channel one) LED will emit light as an indicator that channel one is operational. Channel one works as follows; along the positive rail my 1KΩ LED resistor is placed in series before my yellow (channel one) LED. The Cathode leg has a jumper going from it in order to connect the Cathode leg to the collector of the NPN transistor. At the 5V channel one input rail, there is my 1KΩ resistor running into the base leg (switching circuit) of the transistor. The emitter is connected by use of a jumper to the negative rail. This is the discrete circuit channel one. Channel two works the same, except for the minor difference of my second 1KΩ resistor leading into my second NPN transistor on the channel two 5V input rail. Also at the positive rail my channel two 1KΩ LED resistor and channel two clear LED have to be separated from the channel one components by use of a drill hole after the yellow (channel one) LED and a jumper placed from before my 1KΩ channel one resistor to my 1KΩ channel two LED resistor. This all allows my circuit to run two channels individually.


Test Procedure: To test this circuit you must have a 12V supply and a 5V supply. The Negatives from both power supplies are to be connected to the negative input. The 12V positive is connected to the positive input. The 5V positive is placed on either the channel one or two input of the circuit based on which channel you wish to activate. The yellow LED should light up when channel one is connected and the clear LED for channel two.


Problems: No problems were encountered when making this circuit. I placed in all the components and tested the circuit to find that it worked as it should.

Reflections: Seeing as my circuit worked on my first attempt I would not change how I made or arranged my circuit as there is no need when the circuit works at first attempt.