Day 2 -Using a Multimeter, Introduction to using a BreadBoard, and Schematics, Ohm's Law and Potentiometers

Today, we learned to know how to use a multimeter

We use it to measured:

• Continuity
• Resistance 
• Voltage

First, we took out the solder test board from yesterday and set the multimeter into the correct mode, which is the sound wave picture  (Measuring continuity  can only been testes when circuit is not powered)

By connecting any two point and if there is a number display on the multimeter, then that mean there is some connection.

We were need to find 5 sets of point that are elcetrically connected



Next, we did the Voltage testing
Bascially, voltage comes into two flavors: Alternating Current(AC) and Direct Current (DC)
Examples:
Wall plugs will be a AC and Batteries will be DC

The AC and DC mode for a multimeter are

(The picture on top is DC mode, the picture on bottom is AC mode)

Few important things for voltage testing

• Can only be done when circuit is powered
• Always measured between two points
• Voltage is directional
• DC voltage and AC voltage are very different

Experiment 1: Testing Batteries
By testing the voltage in the battery, we were able to figure out the service hours for the battery
1. Put multimeter in a DC voltage mode
2. The red port goes to positive side of the battery, and the black port goes to the negative side of the battery
3. By reading the voltage shows up on the screen on the multimeter, we can use the following chart down below to determine the service hour of the battery

Result: 1.5 V battery → 1.493V
               9V battery → 7.78V


Experiment 2: Testing wall wart (adapter) plugs
1. Set the multimeter to DC voltage mode
2. Put the red port in the inside and black port on the out side as shown below

Measured: 11.3V3. Now use 2 alligator clips and attach a 100 Ohm resistor across the two multimeter terminal.
4. Remeasure the voltage and observe any changes
Measured: 10.5V



Experiment 2- Testing Wall output
1. Set the multimeter to AC voltage move
2. Measure the wall output and obtaint the number


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Introduction to using a BreadBoard

A BreadBoard is like

And Need to strip the wire again

That is a 10 min work :O

The most important thing is THE RESISTOR!!!

There are two ways to know the value of the resistor
1. Use a multimeter
2. Read the color coding on the resistor

To use a multimeter, we need to set the multimeter into the mode with a Ω on it
Simply clip the two end of the resistor and the reading will show up 

The second way is the learn the color coding on the resistor
The basic rules are

 

LED
THe word LED is Light Emitting Diode

The loner lead is positive and the shorter lead is negative



Light up the breadboard
To light up the bread board, you will need a LED, one at leat 100 ohm resistor and a power supply (which we made on the first day of class)

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Use multimeter to test resistor, potentiometer, and sensor

 The will be the potientiometer
Potentiometeres are resistors taht change value by turing the nub


Sensor

 A Light Dependent Resistor(LDR) is a resistor taht changes value with teh amount of light it reveives
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With the third handout,
Which is available here http://mechatronics.profmason.com/wp-content/uploads/2010/12/Day-2b-Ohms-Law-Schematics-and-DataSheets.doc

The beginning talks about the schematics symbols about all the parts such as bettery and resistors
Later, we use different resistor to change the brightness of the LED

The results are the larger the resistor the dimmer the LED, a smaller resistor make a birghter LED




And we also learned how to read a datasheet for the LED we had
http://mechatronics.profmason.com/wp-content/uploads/2010/12/LED-Datasheet.pdf


It has all the information we want to know about the LED, and most of the time we are able to get the datasheet we need on internet by using GOOGLE




The most important things in this handout are the two laws: Ohm's Law and Kirchhoff's Voltage Law (KVL)


Ohm's Law : Voltage = Current * Resistance
or V= I*R


KVL: In any 'loop' of a cicuit, the voltages must balance; the amount generated= the amount used


By using the two formula's, we were able to calculate the resistance that can make the LED the brightest
The average forward voltage for the LED is 2.2V
and the power supply generates a 5V
so by using the KVL, we obtained 5V-2.2V = 2.8V
And the max current that the LED can hold is 30 milliAmperes(.03A)
So we have  2.8V=.03A*R
When we solve for R we will get 93.3 Ω