canaran’s posterous

1. Momentarily bring pin 2 of the 555 low by touching it to ground. What does the output do?
LED turns on.
2. After LED goes off, do this again and time the LED to see how long it remains on.
4 seconds.
3. Use this formula to calculate how long the LED should stay on:
4.7 seconds.
Does this agree with the time the LED was actually on?
Yes
4. Cause the LED to light and touch pin 4 to ground before the LED would normally turn off. What happened?
The LED stayed on.
5. Change the value of C1 to 0.1 MF. What do you think will be the result of this change?
I think it is because the capacitor (0.1 MF) can keep less voltage in it.
6. Repeat all the above steps to determine the actual effect of making this capacitance change. What happened?
It is all about the amount of voltage that capacitor can keep.
7. You may also wish to change the value of R1 to see its effect. What happens?
Greater resistance we have, more time the LED stays on.

1. Remove one end of resistor R5. This shuts of the opto-coupler. What is the effect of this?

1) Touch the probe to the 5V source. What happens? 

1. By using the four binary switches make the 7-segment readout
display numbers 1 through 9.

2. If any binary number above 9 is made by the switches what happens
to the 7-segment display? Make a chart of how the display looks for
each binary number from 10 to 15.

3. Compare the chart made in question 2 to the one shown here provided
by the maker of the decoder.
( I made a chart of the display and I compared with the chart in the
book. All the numbers were correct.)

4. Use the logic probe made earlier to determine the logic state (high
or low) of the inputs and outputs of the 7448 decoder. Set the input
switches to binary "7"- use the logic probe to observe the states of
pins 7,1,2, and 6. What should they be fore this input? 7 low, 1 high,
2 high, 6 low. Now check the outputs. They are: 13 high, 12 high, 11
high, 10 low, 9 low, 15 low, 14 low.

What switches must be turned on to make the numbers 2,3,5 and 13?
 
For 2, second switch must be turned.
For 3, first and second switches must be turned.
For 5, first and third switches must be turned.
For 13, fourth, third and first switches must be turned.
 
What is the maximum count that can be achieved with 3 LEDs? 7
 
 with 5 LEDs? 31
 
What is the relationship between the maximum count that can be
achieved with a number of LEDs and the weight of the next LED if it
were added?
We can find the weight of the next LED by adding +1 to the maximum
count before we add the next LED.

OPTO DEVICES
 
PROJECT
Logic Probe #1
 
1- Wire the circuit shown in Figure 10, page 9. Touch the input
"probe" wire to the 5V source. What is the result??
The LED lights up.
 
2- Touch the probe wire to the source ground. What was the result?
Nothing changed, the LED didn't light up.
 
3- Explain the operation of this very simple logic probe.
I simply built this little circuit using a LED, a resistance and a 5V
source. This basic circuit is generally used for the pens that checks
whether there is electricity in a surface or not.