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Experiments in Resonance

PostPosted: Sat Mar 08, 2014 12:54 pm
by Harry Dalek
I would normally put this in off topics but the goal and reason is NBTV.

In the past i have played around with vibration idea and always stumped with mechanical movement at the 400 line speed .

I have been looking into the idea just forgetting about trying to match the 400hz with the 12hz movement difference and just doing it small what ever it gives.

Say may be perhaps using a very fine focused laser it would give a ultra tiny raster that could be magnified for a monitor idea.

Studying the vibrating mirror system of the 30s i wondered what the camera was like if there was such a thing and from the patent it was a flying spot camera .

I have not made my mind up what i am doing here as mainly just seeing if its worth a try but with small movements i think a mechanical camera using vibrations ,the light reflected direct to a photo transistors surface the trany could be on one the movements and do way with a mirror that trick has been done before on a larger scale.

Any way there are lots of ways to try this just been playing around with the tuning fork idea as they are very good at keeping frequency spot on this one looks to be a bit high at a resonance of 530 hz .
Could go back to speakers and voice coils the tuning fork may be less noise wise .

PostPosted: Sat Mar 08, 2014 7:48 pm
by Lawnboy
Harry, as you mentioned this I remember a short piece I came across in an old newsletter. If you have the archive CD, check out Vol 32 No 4 pg 10 for a simple scanner made from speakers by Ed Norwill. It looks interesting, especially if paired with a similarly scanned camera, but its also probably quite noisy and obnoxious while in operation.

PostPosted: Sat Mar 08, 2014 9:55 pm
by Harry Dalek
Lawnboy wrote:Harry, as you mentioned this I remember a short piece I came across in an old newsletter. If you have the archive CD, check out Vol 32 No 4 pg 10 for a simple scanner made from speakers by Ed Norwill. It looks interesting, especially if paired with a similarly scanned camera, but its also probably quite noisy and obnoxious while in operation.

Oh looking its the one with the 4 speakers...i had tried speakers a few years ago but not 4 like that, only 1 speaker not to bad on the 12.5 hz and as you say there is a noise problem not so good on 400hz for any mechanical movement .

I swapped to HD voice coils results were much better i recall .

Reading hes experiment again i see the sine wave gave him disappointing results this might be a big problem then for any tuning fork which can only do sine waves.

I wonder on the loud speaker side of things if cutting away parts of the speaker perhaps leaving 3 or 4 Membranes that should cut down the sound and keep the vibrating movement might work.

I did look a little into using the laser movement on dvd drives and vibrating stepper motors might be worth a review .
This fella has done some nice work with what we are talking about

PostPosted: Mon Mar 10, 2014 2:50 pm
by Harry Dalek
Been looking more into the resonance side than trying brute force as in trying to amplify sound .

My experiment today was to see if a electro magnets in this form a solenoid pulsed with either a 400 hz sine wave a square wave and saw tooth would give enough mechanical movement.

I found square wave best and sine wave but i have to retest the sawtooth as it seemed to stop resonating on this waveform .
I am using the laptop as a signal generator and feeding this to a D2012 NPN which is pulsing the electo magnet with a 12v power supply .
I am sure pushing the power supply up a little more might increase the vibrations
like to try later and see if its enough to perhaps magnify for a laser deflection line.
At the moment i am not bothering on with he 12.5 hz side of things as its easy near every way from rocking DC motor to speakers seem to work on this low frequency for mechanical movement .

PostPosted: Mon Mar 10, 2014 9:21 pm
by Harry Dalek
Heres a tuning fork oscillator circuit which happens to be for 400 hz .
I suppose the only problem is making or getting a fork that resonates at 400 hz.
If you make a tuning fork you can test via a mic and as i do using

and its spectrum analyser screen .

You can make the forks frequency adjustable either by adjusting its length or adjuster nuts on both forks i also found shorting the forks at the back with a bit of steel did the same trick a rectangle shape magnet nice easy fix.

Not sure how well on the amount of mechanical movement such a circuit would be for a laser monitor or camera idea but it sounds like its would be pretty accurate clock once it starts oscillating .

PostPosted: Tue Mar 11, 2014 6:34 pm
by Harry Dalek
Because i am trying to make an electrical resonator i should think this should work better as a tuned circuit .

The electro magnet i am using seems to work fine for my experiments so i am as well stick with it .

The inductance of the coil is 14.07 mH from what i can work out with a capacitor of 11.2uF it would resonant at 400 Hz.

I will give that a go and see what happens .

Now i know its worth a shot i will make an oscillator and see what effect if any pulse width has on the thing.

PostPosted: Thu Mar 13, 2014 1:19 pm
by Harry Dalek
I ended up making the clock and electro magnetic drive circuit and that works fine .
Tried an experiment swapping the solenoid with a few relays i had one worked very well even has room to glue on tiny mirror ,i did a quick test with a laser pen on 12.5 hz it gave a laser line almost as good a Hd voice coil ...i didn't glue it on right as it was a quick lets see what happens but it also gave a small 400 hz line best results so far .
I will post some pictures when i have time.

PostPosted: Thu Mar 13, 2014 2:41 pm
by Harry Dalek
Great progress this afternoon both the vibrating stepper motor and vibrating relay at 400 hz both work the stepper is a touch better .
I only had time to do the stepper test for a photo but they are both workable the stepper gives a slight larger line and does work a touch better even at this size ...monitor wise its very workable for a camera it could be tiny.
Great stuff.

PostPosted: Fri Mar 14, 2014 2:37 pm
by Harry Dalek
I tried a few steppers out and i have found the 5 or 6 wire type seem to work best.

I am playing around with the relay idea today out of interest to see what it can do.

The photos posted are a 400 hz test the line is not great size it really depends on distance to the projection screen and brightness of the laser .

I am going to try 2 relays and see if a raster is possible again more than likely small......... rasters eat your laser light up a scan line is one thing a raster is another .

The relays at 12.5 hz give a much wider deflection and all of the above depend on what relay you have some work better than others .

Size wise vibrating ideas will make a tiny compact monitor or camera also without the construction problems of other types of mechanical tv systems .
One thing that comes to mind that it could very well do and a lot easier to construct than any other mechanical way is to go above the 60 line barrier ,i am not sure relays would be great on any thing above 30 line but i have yet to test that we will see.
Speed number of holes slots or mirrors lens make any thing above 60 a nightmare .
Perhaps it is possible with junk to do mechancial MBTV medium bandwidth television where would that start 100 lines over ?

PostPosted: Sun Mar 16, 2014 8:38 pm
by Harry Dalek
I spent yesterday making the second axis circuit for the other vibrating relay mirror.
Made also a PWM circuit of the laser and powered it all up today /

I only have a small laser at the moment for testing so its not overly bright , tried a close distance small raster whole bunch of sine waves close together in this case.

I modulated the laser but could not really make any thing out yet ,i would like to try next swapping the 400 hz relay with the smoother vibrating stepper see what results that gives .

I tried increasing and decreasing the line frequency it was as expected the line size drops with frequency increase and visa versa .the size of any raster done this way will increase with distance projecting but need more laser power .

PostPosted: Mon Mar 17, 2014 6:45 pm
by AncientBrit
Hi Harry,

As it's a tuned circuit are you expecting the scan to be a sinusoid rather than a linear sawtooth?


PostPosted: Mon Mar 17, 2014 11:15 pm
by Harry Dalek
AncientBrit wrote:Hi Harry,

As it's a tuned circuit are you expecting the scan to be a sinusoid rather than a linear sawtooth?


Hi Graham

The Vibrating system can only do sinusoid every thing i have read says it is incompatible with i assume a sawtooth system but i have seen 2 modern examples doing what i am trying and do and they did it a lot harder for 625 line and displaying that fine on a sine wave raster ?,i will post a few pictures and links .

Dr Z would not need this but for us English only readers ... Mirrors%2F

I started off with the same idea for vibrating the line frequency with a electro magnet tuning fork a rod in resonance...i still need to try like these guys have done , but i sort of feel a vibrating stepper motor would have a wide range without having to readjust it mechanically perhaps the forks resonating at that one frequency would do a better mechanical movement i am not sure i am still experimenting .

PostPosted: Thu Mar 20, 2014 4:46 pm
by Harry Dalek
I feel after trying the stepper motor this is the easiest way to do the line scan .
Seeing or comparing the relay to the the stepper its a lot smoother the relay tends to miss lines when doing a raster perhaps something to do with the relays spring.
I suppose the sine wave scan needs some explanation.
Since the fast mirror vibrates sinusoidally, laser traces a sinusoid.
That's why we should delete all odd(even) numbered lines and all odd(even) numbered fields.
A kind of blanking other wise the rocking of the mirror will trace one line forward the next back ...
It didn't really click at first why the modern DIY versions used half the line and frame frequencies since they were doing 625 line so i suppose they are displaying 300 lines or so ,in our case i should try 200 hz but not so good for 6 hz side of things perhaps trying 800 hz and 24 hz without loosing lines.
Any case i was more impressed with the stepper motor vibrating the laser mirror its also much easier to adjust, so far i have only found i think because these things are also like a AC generator it heats my trany so something i need to look into .

PostPosted: Fri Mar 21, 2014 1:25 pm
by Harry Dalek
Today i tried to copy the resonance of a vibrating plate of steel as the 625 line scanners used and its not to bad ,i just used the electromagnet free from vibrating as a solenoid once you get to resonance it does a good job.
The photo of the laser is a bit wonky as i didn't stick the mirror on right and its loose thus the wonky line but thats a pretty good amplified line for that distance it out does the stepper i can see .

Experimenting with the stepper it does fall shot at higher frequencies at 800 hz it was useless really .

I will keep on testing see how it gos .

PostPosted: Sat Mar 22, 2014 9:08 pm
by Harry Dalek
Tried a bit more today on the vibrating steel plate at 200 hz ,the electro magnet seems to work well at this frequency i can get the steel to resonate well ,but didn't have much luck at any thing higher yet .

So far this means the relay and the stepper is better or easier to work up to 400 hz i am sort of thinking it has to do with the size of the electro magnet in the relays case its smaller and so i am pushing it harder as the frequency rises .