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=IR Voltage 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=VI Power 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 V2 Current (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/I 7 = I + 10/I I=2, 5 There 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? Load Battery (V) + - Load

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