Do you have access to a digital oscilloscope or PC oscilloscope? It will make testing/ debugging easier.
Google 'free PC oscilloscope' if you don't want to do this in a college lab.

We'll need to check specific points on the PCB circuit. Firstly, could you post pics (track side and component side) of the circuit you made?

Your new design seems promising. Give it a try, it should work. However, I feel that you are needlessly complicating the issue. As per my conversation with you, you just have to show that the concept works practically. All these complicated 'parallelepiped exhausts and oscilloscopes' are freaking me out. I feel my advice is woefully inadequate here. Just follow your heart and build it. STOP, PLEASE STOP being so theory bound. For heaven's sake - Just do it!

Single motor + fan is enough to create sufficient lift and thrust for a 18" Hovercraft. I have done it with a larger model. No complicated calculations or electronics involved. Remember what we talked about. If an idiot like me can do it, so can you. All the best.

http://www.rcindia.org/boats/scratch-built-hovercraft/

Alas, it's a college project VC sir,  that too for electronics branch. Unless you show them (lecturers) some circuits and complexity, they'll term it as a 'toy'.
I saw a group's project being ridiculed because 'it was made by connecting modules, which anyone could do'. The modules they were reffering to were rc electronics...

I understand Swapnil. That is the pity. Let's help Saurabh to supply as much theory is required so that his professors go into a coma deciphering them!

Frustrating Indian Education System @ 2012.

O you are so humorous VC sir.I do get your point that it should be simple,neat n clean ,the probability of success will then be close to 1.:-)
Swapnil sir,i m posting the link to pics...now what i want from you is to please tell me that 2millisecond pulse means what?
a-the amplitude is 1 for the duration of 2 milliseconds(if this is correct then what should be the OFF time duration?)
or
b-the complete cycle completes in 2 milliseconds(meaning 1(high)for 1ms and 0(low) for 1ms)
   Also, i would like to know that if a circuit is capable of generating 0.5,1,1.5,2 ms pulses (one at a time of course), will the signal(output or generated pulse train) be able to run an ESC or SERVO at different speeds?(just for confirmation)
https://picasaweb.google.com/lh/photo/or4ftsjYnHh3Er8Ju_cBualVV2ZSTrSaGncxjV7WC7c?feat=directlink
https://picasaweb.google.com/111375374001884649365/April82012

The pulse width (on time) must be between 1 to 2 ms.  The time period per cycle must be 20 ms (that is frquency of 50 Hz). Pulse amplitude must be 5 Volts.
I'll check your pics after 6 AM. 

O.K, checked the pics...

1) Why have you used a 50K pot instead of 10K for R4?

2) Do not vary R4 and R5 (in your circuit) simultaneously. R4 is for varying pulse-width and R5 is for frequency adjustment.

3) C1 (100nF) connects to pin 13 and not the junction of R1 and R4.

Make the corrections, run the simulator and post a complete picture of the oscilloscope. Use screen capture instead of camera for better resolution...

Never use 12V for a servo circuit (like you did in the 555 simulation). Always keep Vcc between 4.8V & 6V (5V best).

You should have tried the circuit on a breadboard first...

Some points regarding PCB:
1) Never keep component pins (legs) long. Circuit will be susceptible to noise (particularly this circuit).
2) Solder one end of the capacitor pin as close to the IC pin as possible.


Waiting for the corrected circuit and oscilloscope pics...

In the circuit i have used 10k pot only...(2k pot is absent as you also didnt use 2k pot in ur circuit.)
When i tried to use the circuit to control servo,i failed(but some vibrations and some heating effect was there in the servo- what does that mean?)
In the simulation circuit, i observed that pulse width was not varying with pot adjustment so i tried using 20k n 50k pot.
But now after following ur guidelines, i can see that the pulse width is 2ms and cycle is of 20ms(please to see that).
And,as i remove the connection between the 2k pot key and 10k pot key,i observe that the pulse width remains unchanged(2ms) in spite of varying the pot(0% through 100%).
i am using someone else's computer(no screen capture software installed in this machine), so am bound to rely on camera only.:-)
here is the link to today's pics.
https://plus.google.com/photos/111375374001884649365/albums/5710132455154914689?banner=pwa&authkey=CMuOnajxqdUb
(last ones),Is there any way to obtain desired results without using 2k pot?

Quote from: saurabhreigns on April 08, 2012, 01:45:24 PM
In the circuit i have used 10k pot only...(2k pot is absent as you also didnt use 2k pot in ur circuit.)

I most certainly have used the 2K pot! It's the small trimmer-pot just above the 556!

Quote from: saurabhreigns on April 08, 2012, 01:45:24 PM
...some vibrations and some heating effect was there in the servo- what does that mean?

That means your servo's fried or in a bad state. You shouldn't have tried it before getting simulation results. If the servo still works without jitter or heating-up don't use it till you get perfect servo signals.

Quote from: saurabhreigns on April 08, 2012, 01:45:24 PM
...And,as i remove the connection between the 2k pot key and 10k pot key,i observe that the pulse width remains unchanged(2ms) in spite of varying the pot(0% through 100%).

The 10K pot is the only one that controls the pulse width (and hence the servo position).

Quote from: saurabhreigns on April 08, 2012, 01:45:24 PM
i am using someone else's computer(no screen capture software installed in this machine), so am bound to rely on camera only.:-)
Is there any way to obtain desired results without using 2k pot?

You don't need a screen capture software! Just press the [Prt Scr] key beside the F12 key and paste (ctrl+v) in paint or irfan view. 

The 2K pot is used to get the correct frequency (50 Hz) without which a servo won't work!

The pulse width should vary between 1 and 2 ms only. Beyond those limits your servo might get fried again!

i tried hard but failed to locate the 2k pot on ur circuit board.
where is it?

Hmm... maybe you haven't seen a trimpot before.

Here it is.

If this is 2k pot then where is the 10k pot sir?
i mistook this pot as 10k pot.:-)

The 10K pot, was kept detachable in my circuit. In the above pic there is a pair of male header pins right above the power connector. The 10K pot goes there.

ok....now i got the chunk.:p...thank u sir...i will troubleshoot the ckt tomorrow i guess

 

no fruitful results obtained even after troubleshooting the circuit which,at the end was succeeded to produce 2ms on time with 20ms cycle duration.
Now we are using arduino board for BLDC and Servo control, in conjunction with an IR remote.
Vivek Kumar Singh(rcelectro.com) is helping us a lot.:-)

Oh, he has helped me too! Awesome guy!
You'll surely succeed now! Do keep telling us how it goes.

surely.
acha sir,tel me this.
regarding the design of the craft,tell me which would be better?drilling hole through the hull at 90 degree or at 35-45 degrees(as depicted in sketches i had shown you)

Depends on whether you want to use a single powerful motor for both thrust and lift or separate motors.

I remember a build-thread on RCGroups that started with a single motor design but ended up with separate motors as the single motor design didn't give good-enough speed.

But, you have to demonstrate it indoors, so I guess single motor design should be okay.

We will certainly stick ourselves to single motor design.
Speed is not a requirement ,WORKING is all we will be required to demonstrate..
Now tell me which way should i drill the hole (for thrust)

I have changed the skirt now with the parachute fabric as you suggested VC sir.i am going to use Emax2822 BLDC motor with a 6x3 prop(available).
I want you to guide me if it will work or not coz vivek sir said me today "i dont think it will ever work".
what modifications should i do to make it work if he is thinking right!??https://picasaweb.google.com/111375374001884649365/DropBox?authkey=Gv1sRgCMuOnajxqdUb#5731221990305930946

No I don't think this open skirt will work. The skirt has to be a sealed chamber. Follow this link:

http://www.model-hovercraft.com/2000tdx/2000tdxskirtplan1.html

after a hell lot of time and efforts and ups and downs ,,,we are now done with  succesful test HOVER of our hovercraft.
video link(please see and comment/leave feedback/ suggestions in the comments section)-
http://www.youtube.com/watch?v=Clx1Q4pgplI&feature=youtu.be
image links-
https://picasaweb.google.com/111375374001884649365/DropBox?authkey=Gv1sRgCMuOnajxqdUb#5739455422219636114
https://picasaweb.google.com/111375374001884649365/DropBox?authkey=Gv1sRgCMuOnajxqdUb#5739455490139196002...
VC sir, please give some feedback,we have used the nitrile  pipe for the skirt however the parachute skirt(the silver one) was also doing job(obviously,there were balancing issues as it was a draft and rough one)

toy motor i have .
https://picasaweb.google.com/111375374001884649365/DropBox?authkey=Gv1sRgCMuOnajxqdUb#5739471858400084786