Ballast Resistors and Coil

I took BR2 and BR3 2 ballast resistors.

The specifications

	BR2	BR3
Resistance	0.5 to 0.7R	1.5 to 1.7R

Measured Resistance Values

  The value of BR2 is 1.0R-0.2R=0.8R

  The value of BR3 is 2.1R-0.2R=1.9R

Measuring Current Draw and Voltage Drop

1. Wire up a ballast resistor in series with your coil primary winding values as show in the following diagram.

2. Connect an ammeter in series and note the current draw.

3. Measure the note the voltage drop across the ballast resistor.

4. Measure the note the voltage drop across the coil primary.

The current in the series circuit

The voltage across the coil

The voltage across the ballast resistor BR3

Current	Voltage across the coil	Voltage across the ballast resistor BR3
3.57A	5.27V	6.15V

Calculation

Rt=Rcoil + Rbr3= 1.4 + 1.9=3.3R

I=V/R=12V/3.3R=3.6A

Vcoil=IR=3.6A x 1.4R=5.04V

Vbr3=IR=3.6A x 1.9R=6.84V

The calculated values are close to the measured results. Because the power supply is close to 12V.