Discussion in 'Homework Help' started by carbee, May 23, 2013.

1. ### carbee Thread Starter New Member

Oct 26, 2010
2
0
design a faulty-lamp indicator that monitors 64 lamps at the end of an airport runway. When the lamp is operating, the voltage at that lamps terminal is 5 V. When the lamp is faulty, the voltage is zero. The output of the indicator must have two 7-segment LEDs that indicate the number of the lamp being tested (0 to 63). If a fault is detected, a single LED must light to indicate that the lamp at this number position is faulty.

i badly need a simple idea on how to design this using flip flops and logic gates. thanks

2. ### LDC3 Active Member

Apr 27, 2013
920
160
Since there are 64 lights, it makes sense to arrange them in a grid of 8 x 8 so you can use multiplexing to address each light individually.
You can use the address as the 2 digits being displayed (in octal).

3. ### carbee Thread Starter New Member

Oct 26, 2010
2
0
given this materials:

IC Number Quantity
74LS92 2
74LS90 2
74LS161 2
74LS160 2
74LS47 2
74LS151 1
555 Timer 1
330ohm DIL resistor module 2
1 k ohm 2
2 k ohm 1
Trimmer pot 1M ohm 1
1N914 diode 1
7-segment LED Display (common anode) 2
LED (red) 1

4. ### bountyhunter Well-Known Member

Sep 7, 2009
2,498
507
This sure looks like a class assignment. No sane person would tell an engineer to design something and give them a restricted list of parts to use.

5. ### tubeguy Well-Known Member

Nov 3, 2012
1,157
197
For the multiplexing to work with the parts listed, I think you'd have to assume the 'landing lights' are not real lights, but more like low-current LED's.

6. ### sharivan New Member

Mar 17, 2013
18
0
i have a design for this except for the part on how a single led light indicating if a certain number position is faulty..
acheche

7. ### WBahn Moderator

Mar 31, 2012
18,093
4,920
While it is tempting to do this, it won't meet spec. The specification states that the number to be displayed is to be 0 to 63.

8. ### WBahn Moderator

Mar 31, 2012
18,093
4,920
Actually, this is the norm in digital IC design. You have a standard library of parts and that is what you have to use. Because of the time an effort involved in adding a new component to a library, you only did that if it was absolutely necessary. For some of our chips, the library (which were almost always done in house because our needs were very different than most houses in that we could tolerate larger standard cells but could not tolerate the noise the foundry's standard cells produced since our designs were mixed-signal with the focus on low-noise analog performance) consisted of only about a dozen cells.

But, in general, I agree with you.

9. ### WBahn Moderator

Mar 31, 2012
18,093
4,920
Or assume that the lights have a "test port" that outputs 5V when lit and 0V when dark.

In any event, you have to base the design on the information provided in the client's spec and if the information is wrong, then that is on the client. In practice, of course, a good engineer will question parts of a spec that don't seem to make sense and ask the client to at least verify that the spec is really what they want in light of the concern that they present to the client.

tubeguy likes this.
10. ### WBahn Moderator

Mar 31, 2012
18,093
4,920
This is a pretty important thing that you neglected to include in your original question. When you ask for guidance about a design, please tell people the constraints that are being placed on that design.

Also, as this is homework, you are expected to offer up YOUR best attempt to solve YOUR homework. This is not only important because we aren't going to do your homework for you, but we also need to get an idea of the level of your thinking and your approach. We can then tailor our feedback so that it guides you along a path from where you are to where you need to end up but do so in a way so that you have made most of the actual steps, which maximizes your learning.

A first step would be to write down an algorithm for performing the test. What has to happen, in sequence, to test the lights? Start with what has to happen to test a single light.

11. ### tubeguy Well-Known Member

Nov 3, 2012
1,157
197
To borrow a phrase.. "I (also) learn something almost every day from this site"