How Can I Troubleshoot and Understand the Model Lighthouse Project Circuit?

[Maj812]

I'm a final year student n the course that i am taking is Electronics and communication engineering.I'm doing a final year project called the model lighthouse project.
Heres the link: http://www.kpsec.freeuk.com/projects/lighthouse.htm
Please help me as this is my first time writing and doing this project. Here are few questions:

1) I tried redrawing the circuit using multisims but the lamp doesn't want to light up.I have tried moving the potentiometer % to the lowest, but it still doesn't want to show me any output...Is it something wrong with my connect or ...?
I have attached my redrawn circuit.

2) Please give me a simple explanation on how this whole circuit flows.
3) Any idea on how to draw the block diagram of this model lighthouse project

Sorry if i give too lil info..if so..please do tell me..Thanks in advance =]

 

[vk6kro]

Pin 5 of the 555 should not be grounded. It is usually OK to leave it open circuit.

The 555 generates pulses about once a second and these turn on the outputs of the 4017 in sequence.

Each time an output that has a diode connected to it is turned on, the transistor is turned on and the lamp should light up.
So you can do simple programming to get the light to turn on in any sequence you like as long as it doesn't involve more than 10 steps.

 

[Maj812]

ok.for pin 5 i have remove the connection and leave it open..but still when i start to stimulate it using multisim, it doesn't seem to light up..I still can't find wats the problem with it ><" Is the rest of my connection correct? Can u help me find the solution for this?



Thanks for replying.

 

[vk6kro]

The rest looks OK.

Bring the oscilloscope probe to Pin 3 of the 555 and ground and see if there are slow pulses there. I make the frequency about 0.6 Hz. It should look like a square wave.

If there are pulses there, check for pulses on Pin 3 of the 4017. These will be short pulses with a long gap between the positive-going parts of the waveform.
There should be similar pulses on the other output pins of the 4017.

Then come back here. That should help to narrow down the problem.

 

[Maj812]

Hey,sorry for the late reply.

About the frequency, may i know where to change it?At which component?
Does the freq affect the pulses if u change it??

Thanks a lot for replying.=]

 

[vk6kro]

The 100 K, 1M and 1 uF capacitor change the frequency. Decreasing any of them will increase the frequency. You also have to keep the resistors in that ratio (1 to 10) to get the wave shape to be the same.

You could try this calculator:
http://freespace.virgin.net/matt.waite/resource/handy/pinouts/555/index.htm

Enter resistor values in K, so 100 K and 1000 K

The shape of the waveforms should be the same, although the frequency will change, of course.
Did you try looking at those pins with the Oscilloscope?

 

[Maj812]

Sorry for the very late reply again.><"

Hmm..about the frequency again, i still can't find it..cause in my multism version 10,the properties,they don't show any bar for me to change the frequency.><" so how?><"

And if u don't mind, can u read my basic operation of the circuit.(I wrote this from my understanding by looking at the circuit diagram). If there's any mistake i have made, please correct me.><" Thank you so much in advance!

Basic Operation of Model lighthouse.
•When the switch is on, current flow and the 555 timer will be triggered. The 555 timer is used to charge and discharge to produce a clock pulse at pin 3. In this project, the 555 timer is in astable mode where it gives a continuous series of clock pulses. It charges and discharges at different time high(tH) and time low(tL) depending on the 100k and 1M resistor and 1uF capacitor as well which is connected to the 555 timer.

•The 1M potentiometer is used to control the time period of the 555 astable from about 0.1s to 1.5s.

•Next, the 4017 decade counter will receive clock pulses at pin 14 from output pin of 555 timer. As the 4017 decade counter receive the clock pulse, countering and decoding will occur where it has output from Qo-Q9 and each one becomes high(on) in turn as it received the clock pulses.

•The output of 4017 at Q0, Q1, Q3 and Q4 are connected to the diode to produce the flash sequence. The 2k2 resistor is used before the transistor so to limit the current flowing to the transistor (base) as it only requires little amount of current. The BC108 transistor is used to amplify the current to power the 6V lamp.

 

[vk6kro]

The description of how the circuit works seems OK.

The calculator for designing the 555 astable circuit works the other way. You guess some resistor and capacitor value and it gives you the frequency.

It also gives you a formula for working it out, so you could rearrange this formula and get it to work the other way around and give just a capacitor value for a given frequency and resistors, for example.

This formula was F = 1.45 / ( R1 + 2 R2) * C so you would just exchange the F and the C remembering the C is in Farads.

 

[Maj812]

thanks for replying n sorry for the late reply again.

Okie..i get what u mean but if i change the resistor and capacitor's value, won't it be not according to my project?Coz my project states tat the required value for resistor and capacitor is 100k & 1M ><"

 

[vk6kro]

Hey,sorry for the late reply.

About the frequency, may i know where to change it?At which component?
Does the freq affect the pulses if u change it??

Thanks a lot for replying.=]

You asked how to change the frequency but then you said you had to use the same components for your assignment.

Sorry, but you can't change the frequency and keep the same components

 

[Maj812]

About my model lighthouse...How to check how much current is flowing to my circuit?? and for my output..i can't get my "MES lamp" to light up..but if i replace it with a LED,it lights up.Is there anyway if i could get the MES lamp to light up??