Introduction to Electronics

Basic Electronics

• What is electricity?• How is it measured?• Terms• Ohm’s Law • Kirchhoff's Laws• Power• Putting it together• Power Distribution

What is electricity

• Electricity is the flow of electrons in a conductor

• Electricity is measured in:– Voltage (V) – similar to pressure, this is the force

available to drive the electricity measured in Volts– Current (I) – this is the flow of the electricity

measured in Amps– Power (W) – this is the power used or available

measured in Watts

Other electrical terms• Resistance

– a measure of a material’s resistance to the flow of electricity– measured in ohms Ω

• AC Current – current that flows first in one direction then in the opposite direction

• DC Current – current that flows in one direction

• Open Circuit – a broken current path

• Close Circuit – a complete current path

• Short Circuit – when current does not flow where intended

Ohm’s Law

V=IRVoltage equals Current times Resistance

• What can cause Resistance?– Wires; the smaller the wire or the longer the run

the greater the resistance– Circuitry– Bad Connections– Anything between the power source and the load

Identify

Kirchhoff's Laws

• Voltage – There must always be a closed path for current to

flow– Summation of voltages around any closed loop is 0

• Current – Summation of currents into a node must equal 0

Power

W=VIPower equals Voltage times Current

• 746 Watts = 1 Horsepower

Putting it together

Simple Circuit

If V is 10 Volts and R is 10 ohms, what is I?What is the power used by the Resistor?

Resistor (R)Battery (V)

+

-

V1 V2Current (I)

Motor Circuit

If V is 10 Volts and RM is 10 ohms, what is I?What is the power used by the Motor?

If V is 10 Volts and R and RM are 10 ohms what is I?What is the power used by the Motor?

Putting it together cont.

Motor(RM)

V

+

-

V1 V2

R

V3

I

Putting it together cont.

The resistance of a motor is not simple and does not follow the previous example the amount of current used by a motor is dependent on the load. Let’s redo the previous calculation assuming the motor has a 10 Watt load.

Putting it together cont.Motor Circuit

If V is 7 Volts and R is 1 ohms and the Motor uses 10 Watts, what is I?7 = V2 + V3

W = VI => V = W/I7 = I + 10/I

I=2, 5There are two answers, how can this be? As the voltage drops the motor will slow down, producing less power, reducing the need for current - even

here the motor is not linear

Motor(RM)

V

+

-

V1 V2

R

V3

I

Application

• How do we reduce the resistance to the motor?– Larger Wires– Shorter Wire runs– Better/Fewer connections

Power Distribution

• What is Power Distribution?– Providing power from the battery to the devices

that need it.• Why is it important?– Safety– Clean distribution • efficient and allows for better performance• Easier modification and troubleshooting

Power Distribution

• What does it look like?• One device or load• What about more?

LoadBattery (V)

+

-

Load Load

Power Distribution

• How is it done in FRC?• Electrical Hardware• Wiring Diagram• Control Diagram

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