Basic Circuits – Lab 1 Xmedia Spring 2011

Basically Power –Provides energy for the sensor and the output Sensor –Changes aspects of the circuit based on input Output –Changes based on the sensor

Solderless Breadboards Used to prototype circuit designs

Lighting an LED Battery Resistor LED

Battery Potential Difference - Voltage –Like potential energy Positive (VCC, +) and negative (Ground, –) Note about complete circuits 9 Volts1.5 Volts

Resistor Resistance – Ohms – Ω –Limits the current

LED Light Emitting Diode –Directional –Brightness based on current

Lighting an LED Build this circuit Observe the light turn on when you complete the circuit

Fading and LED Battery Resistor Potentiometer LED

Potentiometer Variable resistor –Changes the resistance in the circuit Positive, negative, and variable legs

Fading an LED Build this circuit Turn the knob Observe the LED changing brightness

Some Theory Voltage Resistance Current Ohm’s Law Calculating LED Resistor Values

Voltage V Potential difference Energy per unit charge Drives the current between two points in a circuit DCAC

Current I Flow of unit charge per unit time –Ampere – Coulombs/second DCAC

Resistance R, Ω Opposition to the flow of current –Based on properties of the material –Conductor vs. Insulator

Ohm’s Law Relates voltage, current and resistance I = V / R –V = I * R Units are important – amperes, ohms, volts –Not milliamps, and millivolts

Calculating LED Resistor Values LED Voltage and Current from data sheet –Typically ~ 1.7V –Typically ~ 20mA Know supply voltage – for example 5V Resistor needs to take the extra voltage –5 – 1.7 = 3.3 V Ohm’s Law – R = V/I = 3.3V/0.02A = 165Ω

Multimeter Usage Connections: –Black - COM / Ground –Red - 10A, 300mA, V/Ohms Continuity Test, Diode Test, Resistance, Voltage, Current Specs: –DC voltage range: 326mV V –AC voltage range: 3.26V - 750V –DC/AC current range: 326µA -10A –Resistance range: 326ohm Mohm Mastech MY68 Autoranging

Multimeter Usage Continuity Test – To check if two points are electrically connected, audible beep sounds if they are Diode Test – Diodes only allow current to flow in one direction only, they have a positive (+) lead (i.e. anode) and a negative (-) lead (i.e. cathode) – LEDs are diodes that emit light – You can test the polarity of a diode using a multimeter set to "diode test" mode – Connect the black lead to (-) and the red lead to (+) and the diode will conduct. Connected backwards it will not.

Multimeter Usage Note: in manual range mode, always make sure to select the correct range before connecting the multimeter leads!! Resistance - Ω – Remove component from the circuit Voltage - V – At a point in a complete circuit – Connect black lead to ground, red lead to the point in the circuit DCAC

Multimeter Usage Current - A –Use the 10A jack until you're sure that the current is less than 300mA, and set the range before connecting the leads! –Current is measured in series with the circuit: Turn off the power Break the circuit Put the meter in series Turn the power on DCAC

Lighting 3 LEDs in Parallel Each LED gets its own resistor Build this circuit Measure the voltage across each branch Measure the current out of the battery and before each LED

Current Split - Parallel Sum of the current through each branch equals the current from the power source Voltages are the same in each branch 1/R total = 1/R 1 + 1/R 2 + … + 1/R n

Lighting 3 LEDs in Series One resistor for all the LEDs Build this circuit Measure the voltage across each LED Measure the current out of the battery and before each LED

Voltage Split - Series Voltage across each component is different Current through each component is the same R total = R 1 + R R n

Voltage Divider V out = V in * R 2 / (R 1 + R 2 ) If R 1 is variable, as R 1 increases V out decreases

Variable Power Supply Output connections in Volts DC (direct current) –Red: power –Black: ground Specifications: –1.5 to 30V DC output 0 to 1A output current 100 to 240V AC input Over-voltage/current protection Short circuit protection