The problems we confront while designing an elevator circuit

Don't worry, I'm gonna post the design of ours with pspice later .. today I just had time to post that .. It will continue ..

In our design we have two inputs. IN1 is to choose the way you wanted to go and IN2 is to stop the elevator on which floor you want. After the design procedure we came the real part : setting our circuit up. In this part we spend a lot of time to see the result we wanted to. Because there was really lots of reasons to keep us out of the way.

In our early times at laboratory we set a circuit that we both examined while setting the circuit elements for keeping our circuit out of trouble from connection errors. After we finished the circuit, before plugging the VCC on we make sure that the JK flip flop’s K parameter is converted with NOT gate as we follow on datasheet. And PR and CLR legs of JK flip flop are both 1 to see the behavior of synchronous circuit. After we plug 5V dc voltage we saw that something was wrong. The circuit was not answering our inputs according to clock signals. We were taking the signal from TTL(transistor transistor logic) output of the generator. This output is supposed to give us 5V and it must be independent from amplitude bar of the Function generator. We examined the output of the function generator on the oscilloscope and see that the TTL output was not working properly.

After changing the output of the generator we plugged the Voltage connections again and with a bit of excitement we rushed to see the result of our circuit. It was failure again. Plus we smelled something was burning. After a second we realized that it was coming from our circuit, JK flip flop. We unplugged the sustention safely with our right dry hands and sniffing the brief and weird smell in our lungs. The voltage was supposed to be 5V as we examined before we plugged the circuit. We listened the lab attendance suggestion and examined the voltage again and we saw 20V on the oscilloscope screen.

So we changed our cadet . But we were not sure about if all the gate’s were burned out. So we decided to inspect all the legs of the gates to make sure that everything was alright with our circuit elements. We keep following that procedure and we found something interesting. In some integrated circuit some of the leg’s were working but some of them weren’t. So we changed that half-burned integrated circuit’s with brand new ones. But before changing them we tried all the integrated-circuits we bought before using.

After changing circuit elements we still couldn’t got the result we want. And yes we felt a little tired of that. Because we set that circuit like ten times and we were able to remember those functions we found on the design procedure and the proper legs of the integrated circuits. But still couldn’t get it to go. Everything was right and every connection was correct. We suspected from our design and set it on the workbench. We were getting the results we want. So our design was also true. What was the problem ?

This time we used a different method while inspecting the circuit. We started to touch with the probe to the leg of the integrated circuit not the potential line to see if there might be any difference between the gate voltage and the potential line. Then we inspected the board which we inserted the circuit-elements. There were same voltage potential on different voltage lines. That means there was a short circuit under the circuit board. Then we found several of the on the other sides of the board. The reason of that short circuits might be the cables that we used on our circuits. We were using those boards for 2 years and including our freshman year. In our freshman year we might pull that cables not kindly and cause the cables to trap under the circuit board. Those conductor peace’s we left inside the board might cause a problem after while we tried another cable for another circuit later. After a quick chat with lab attendance he showed us inside the boards that we used in our experiment. We looked at the design and It’s a miracle to keep that board out of any trouble. So we decided to keep our cable’s conducting parts on optimum length.

And after 40 minutes we had a circuit with result !!

We played a little with our circuit parameters to see what are the really effective on the result. After all we become really familiar with some of them:

We must use same kind of cable. At the lab in the cable box there are some cables like we used in our circuits but a little bit chubby ones. After we finished our circuit and see it working properly we changed one of the cable inside of our circuit with that chubby ones and observe that with time the operations which our circuit do becomes a weird with time. The bit that which has the chubby cable inside the connections has becomes a little faster with time. We came to the conclusion as a group that if we would change the clock frequency with higher frequencies there might be huge problems on the outputs.

We must use the same firm’s integrated circuits. If we use different kind of integrated circuit there might be some problem with our output lines because of the propagation delay of our gates. With higher frequencies that problem can grow bigger and bigger.

We got out of the laboratory and looked at the sky. There was a rainbow on the sky. But we were able to see only two legs of the rainbow. The middle part was disappearing with the clouds. And here its our dialog:

A-Look at the rainbow!

B-Look there is another one there …!

A-I think they are same. Follow it to the clouds . They are disappearing in to same cloud.

B-Are you sure ?

A- …

B-…..

A- Alright!! Get me the scope and a probe! :):):)