Circuit diagram
A component list
2 X 330R
2 X 1K3
2 X BC547 Transistor. http://pdf1.alldatasheet.com/datasheet-pdf/view/11551/ONSEMI/BC547.html
Calculations
To work out what resistor to use with LED
Rs=(Vs-Vled)/IIed
Rs=(12v-2v)/0.035A (35mA)
Rs=285ohm closes to E12 group resistor is 330R
To work out what resistor to use with transistor
Beta=IC/IB
IB=0.035/110
IB=0.000318 (0.3mA)
Rb= (V-Vtrans)/I base trans
Rb=(5v-0.7v)/0.000318
Rb=13,314 ohm closes to E12 group resistor is 15K
Lochmaster
A Technical Explanation of how the circuit works.
What this circuit does is convert a 5v E.C.U signal to 12v to power a 12v component eg injector.In other words it uses the 5v to switch to 12v
In more details 12v is the main power supply (red + and black -lead) this 12 volt passes through the resistor ,led and onto the collector.
Negative is hooked up to black and 5v is then hooked up to the yellow or white lead this connects to the transistor base which in turn when 5v is pass through the transistor acts like a switch and enable 12v to pass through to the emitter.
Both led should be off when hooking it up to 12v but when 5v is pass through one of the signal leads one of the led should light up.
The avalible voltage to collector
Same as Vce.
This is a good result, ideal should be 0v but this is very near. datasheet says 0.5 saturated Vce
The avalible voltage to base
voltage at emitter
Problems
The circuit did not work the first time. This was trace to a faulty transistors. when test with a diode tester base and emitter displayed O.L both ways this indicates that there is a open circuit in the transistor.
Reflection
If i was to do it again i would test all the components first .
Also made sure i was drilling the right spot before drilling, i auctily drilled a row across and when i went to put all my components in one of the legs had no copper connection to solder to. i solve this by bending the legs across.
Finish result
