Injector Circuit Write-Up

Parts:

• Vero Board
• Jumper wires x5
• R1+R2 resistor 470R Correction : 0.5W
  
• R13+R16 resistor 100R Correction : 0.5W
  
• BJT Transistor NPN type BC 547 x2
• LED 1 2V 5mm 30mA Yellow
• LED 2 2V 5mm 30mA Red

What it does: ECU operated, switches injectors at high speeds.

How it Works: First of all the circuit must be connected to a Vs of 12V. This sends current through the Resistors and LED's to the Collector terminals each BJT.
In order for the LED's to operate current must also be sent to the Base terminal of either BJT from either 5V Vs'. This switches the BJT fully on (saturated) and thus lights up the LED. This 5V supply can be switched to either BJT so as to turn either LED simultaneously. To complete each circuit each Emitter terminal of the BJT's is Earthed at the 0V rail of the Vero Board.

Test Procedure: To test this circuit you must have a 12V supply and a 5V supply. The negative wires from both power supplies need to be connected to the negative wire on the board. The 12V positive wire is connected to the positive wire on the board. The 5V positive wire is placed on either the channel one or two wires of the circuit depending on whether channel you wish to activate the Yellow or Red LED. The yellow LED should light up when channel one is connected and when channel two is connected the Red will light up.

Calculations: Finding the values of my resistors.

R1 = 12/0.03mA = 400 ohms (470R)

R2 = 5 - 0.7 = 4.3/0.09A = 47 ohms (100R)

Problems: No problems or faults were encountered whilst making this circuit.

Reflection: If I were to do this circuit a second time I would not do it any differently apart from seeing if at all the amount of space on the board could be reduced and not drill my holes as large as I did.