Timing resistor - Capacitor circuits with voltmeters

TTEC 4841 - Electrical and Electronics- Practical

26/8/2011 tuesday

start = 1.00pm finsh = 4.30pm

In todays task we learned about timing resistor - capacitor circuits using a voltmeter.

First thing we did was to idintify the electroytic capacitor the Black side is the negative and the white side it the positive.

Then we moved on by writing what is a capacitor.? capacitors are used to store eletric change and prevent voltage spikes. the negative plate area provides a form of reservair into which electrons can flow and this stores any excess of voltage.

Then we moved on by calculating how fast the capacitor should charge using the formula =( R*C*5*T )

capacitance ( uF )	capacitance ( F )	*	resistance ( ohms )	*	5	calculated time ( second )
10	0.00001	*	1,000	*	5	0.05
1	0.000001	*	250,000	*	5	1.25
100	0.0000001	*	10,000	*	5	5
300	0.0003	*	4,5000	*	5	6.75

Then we did evaluate the charge Time

capacitance	yes	no
10 uF		no
1 uF		no
100 uF	yes
300 f	yes

 Then we calculated resistor size , we got given servel capacitors of different sizes.

	capacitance ( uF )	capacitance ( F )	*	5	=	Answers ( A )
1	330	0.00033	*	5	=	0.00165
2	100	0.0001	*	5	=	0.0005
3	0.47	0.00000047	*	5	=	0.00000235
4	10 micro	0.00001	*	5	=	0.00005

Then we divided 180 ( seconds ) by the answers A to calculate what size ressitor will be needed to have the capacitor charge in about 3 minutes

	calculated time ( seconds )	/ by	Answer (A)	=	Resistance in ( ohms )
1	180	/	0.00165	=	109090.91
2	180	/	0.0005	=	360,000
3	180	/	0.00000235	=	765,957,45
4	180	/	0.00005	=	3600,000

Then we moved on doing By building a capacitor charging circuit using the following things

Components

• 1 * resistor
• 1 * capacitor
• 1 * bridging wire
• 1 * voltage source ( battery or power supply )

Then we moved on by monitoring the capacitor charge with a time verse voltage.

Then we moved the bridge wire and recoreded the voltage every 5 second for 3 minutes approximately.

which that gave us a graph of plot the capacitor charge up time on the graph.

over all this showed us that the voltage started low then it build its way up.

 with our graph our resistor over charged and stopped at a surten spot which was 8.29 so it was hard to get volts in. if theres more capacity its easy to get volts in there as its fully charged if theres less capacity its hard to charge. so its start going higher where it it stopped at a surten place which was 8.29

Testing Diodes

TTEC 4841 - Electrical and Electronics- Practical

26/8/2011 tuesday

start = 1.00pm finsh = 4.30pm

In todays task we learned how to measure diodes with , diodes test.

First thing we had to do was to identify the direction of flow through the diodes.

which is Anode, catthode, and current flow.

Then we moved on by measuring the resistance (ohms) of the diodes in both directions using the 2k ohms on multimeter.

Anode to cathode=  infinity ohms
Cathode to anode=  infinity ohms

 Then we checked the voltage supplied at the meter probes in the ohms position, with another meter set on Dc volts while the meter set on 2k ohms position,

= 0.24 v

Is this enough voltage to theoretically push through the bindery layer of the diode and get an accurate reading ?  NO

• Did the ohms measurement work? no beacuse theres not enough voltage pushing through the bindery layer of the diode.

Then we set our multimeter to diode to test the position using.

• Anode to cathode = 0.624 v
• Cathode to anode = infinity v

This shows that it will be from anode to cathode the is a pathway but from cathode to anode the is no electricity crossing.

Then we Build a circuit with a diode and resistors. we buld the circuit with a 1kohms ( 1000 ) resistors and used 12 volts supply.

• Measure the voltage drop across the resistor ( R ) = 11.87 v
• measure the voltage drop across diode ( D ) =  0.56 v
• measure the amp flow through the diode = 0.00 a
• measure the available voltage at supply ( Vs ) = 12.44 v
• add the voltage drop across R and D .  VDr + VDd = 12.43v

Then we applied the rules of electricity? The voltage drop in the resistor is the highest in the circuit which that leves a small amount of voltage for the diodes, so with the amount of small voltage left for current to flow in.

Then we changed the resistance by placing the resistor with a higher value resistor to the circuit.

• what size resistor did you put in = 1 k
• measure the voltage drop across R = 11.72 v
• measure the voltage drop across D = 0.68v
• measure amp flow through D 0.02 amp

The resistance R and D goes higher as the amps stays the same.

Then we test an LED ( ligh emitting diode ) with a meter in the diode test posistion to measure the LED in both Directions.

Anode to cathode = 2.32v
Cathode to anode = infinity v

Then we compare the voltage drop of a normal diode and an LED.? The voltage in LED is higher because the voltage is used to push mps through the LED but in diode theres no current flow so theres no amp flowing through.

Then we build a circuit with an LED

• measure the voltage drop across R = 10.30 v
• measure the voltage drop across D = 1.84 v
• measure amp flow through LED = infinity
• measure the available voltage At Vs = 12.15 v
• Add the voltage drop R+D = 12.14 v

This showed us that the voltage drop in LED is higher becasue LED has more resistance while its turned on.

Identifying , testing and combining Resistors

TTEC 4841 - Electrical and Electronics- Practical

25/8/2011 tuesday

start = 1.00pm finsh = 4.30pm

 In todays task we identifying , testing and combining Resistors

First thing we did which was Indentification and combining practice:

1. we had to obtain 6 resistors of different values.

• which we used the colour codes to calculate the value of the resistor
• measure the resistor value with a multimeter.
  

  band colour and calculations	measure value ( multimeter reading)	low tolerance value	high tolerance value	pass of fail
  82*1=82 ohms	81.4 ohms	77.9 ohms	86.1 ohms	pass
  68*1= 68ohms	68.4 ohms	64.6 ohms	71.4 ohms	pass
  68*10,000= 680,000 ohms	670 kohms	646,000 ohms	71.4000 ohms	pass
  68*100,000=6800,000 ohms	infinity	6400,000ohms	7140,000ohms	fail
  10*100 = 1,000 ohms	993 ohms	950 ohms	1050 ohms	pass
  82*10,000 = 820,000 ohms	820 kohms	779.000 ohms	861,000 ohms	fail

  
  
  
  
  This showed us how to see the colours of resistors and can be identified by a code using colours and position of the bands.
  
  
  • Then we moved on by choosing two resistors and record their individual ohm resistance value using a multimeter.
  • Resisor 1: 81.4 ohms        resistor 2 68.4 ohms
  
  
  • Then we put two resistors togather in series  ( end to end , one right after another ) measured their combined value    1 and 2 in series = 148.6 ohms
  
  
  • Then we put two resistors togather in parallel ( connect the ends when they are side - by - side ) then measured the combined value   1 and 2 = 37.1 ohms.
  
  
  This showed us in series the resistance adds up in parallel . so the resistance is divided by two. in parallel RT is always lower than the lowest branch of resistors.