Jeffree cell

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Postby Harry Dalek » Sat Sep 10, 2011 6:19 pm

johnrpm wrote:Harry,
Yes the mirror faces have to be very accurate, have you considered polishing a hex nut, they are surprisingly accurate, an M10 nut should be big enough,
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Hi John i did some experiments on the stainless steel nuts for a polygon mirror replacement ..The M10 is fine but theres a defocus of the laser dot ,i tried a lot of different ones ,the metal reflects well but does drop the focus and light levels a bit ..I have ended up using a large flat nut from a large RF plug...this seems the best for distance but still using it works best if its as close to the screen or next reflecting mirror.

The results are not to bad not as good as a glass or plastic mirror but as you say they are accurate and when i need one quick i know what to do .

When i take some photos i will post .
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Picture 232.jpg
Tried to do my best with a laser pointer in one hand and a camera the other !
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Picture 243.jpg
sorry about again bad picture this time hand spinning hd as well doing the other perhaps i am an octopus !
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Picture 256.jpg
These are the nuts i am using for the polygon
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Picture 255-crop.jpg
Just an idea for testing with some spare bits
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Picture 254-crop.jpg
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Postby johnrpm » Mon Sep 12, 2011 7:28 am

Harry,

sorry for the late reply, first chance to turn on the pc for 3 days, here is an image of the connections for the polygon, I shall post more info when time permits, your polygon mirrors look good, looks like you are close to getting good results, and at low cost, Gary's looks nice also.

The crystal cutting has gone well, I have done 4 cuts now, just cutting away the tip and base for practice, 2 things I have learnt, the correct grit (150) makes a big difference to cutting speed, and having a "well" of grit to constantly replace the brass disc with fresh grit, the next step is to cut the actual crystal for the jeffree cell, cutting is not very acurate so must be oversize, then I need to make a lapping plate to replace the brass disc to polish the crystal down to thickness.

I like the look of this project, http://laserpointerforums.com/f47/homem ... 32628.html
He uses resonance, which is very simple and cheap, although I think he uses blanking on flyback, so not NBTV, but his results look good.

p.s yes bldc motors are similar to steppers, on wikipedia is a good link with an animation. http://en.nanotec.com/steppermotor_animation.html
select the motor type and the animation shows the sequence for coil energising.
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Postby Harry Dalek » Mon Sep 12, 2011 8:48 pm

johnrpm wrote:Harry,

sorry for the late reply, first chance to turn on the pc for 3 days, here is an image of the connections for the polygon, I shall post more info when time permits, your polygon mirrors look good, looks like you are close to getting good results, and at low cost, Gary's looks nice also.

The crystal cutting has gone well, I have done 4 cuts now, just cutting away the tip and base for practice, 2 things I have learnt, the correct grit (150) makes a big difference to cutting speed, and having a "well" of grit to constantly replace the brass disc with fresh grit, the next step is to cut the actual crystal for the jeffree cell, cutting is not very acurate so must be oversize, then I need to make a lapping plate to replace the brass disc to polish the crystal down to thickness.

I like the look of this project, http://laserpointerforums.com/f47/homem ... 32628.html
He uses resonance, which is very simple and cheap, although I think he uses blanking on flyback, so not NBTV, but his results look good.

p.s yes bldc motors are similar to steppers, on wikipedia is a good link with an animation. http://en.nanotec.com/steppermotor_animation.html
select the motor type and the animation shows the sequence for coil energising.



Hi John

Thanks for the polygon info ! arrr thats how they work ,i will try it out on the next one i printer polygon i scrap.

Having the polygon on the Hd the little disk that holds the platters on is very reflective due to all that red you see in the pictures ...i have it near on covered now with as you see some spokes for each mirror that i hope via a LDR and a transistor switch controling a monostable and then a H Bridge circuit will run the vertical 4 sided mirror .Just an idea i am testing out as need to test this faster speed for my other project as it needs the same sort of idea for it and i do like playing with mirrors :wink:

Boy the jeffery cell is pretty hard to make ! well close to the original ! i don't think there are many people that can cut that crystal ,how long do you think it will take and are you making a spare ?

OH i have known about that guys laser system or a while they were hating him on that forum because he would tell them bits about he's system ...i think he wanted to make money from it which is strange as they use micro nano mirrors ? these days anyway to do they same thing 100 times better ,,,i was never sure if he was telling the truth about hes design in full.

Keep on that jeffery cell i was wondering what the damping wall is made of other end of the cell just the metal wall have to do some more reading .
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Picture 258.jpg
heres my test bed for a 2 mirror idea
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Postby johnrpm » Mon Sep 12, 2011 10:58 pm

Hard disc and cd drives also use bldc motors, so they could be driven directly, with the right circuit, ( I had thought of using an arduino) maybe one of the electronic experts could suggest a circuit?,
Just an idea, but I wonder if one of the disc platters could be bent, or should I say formed to make the laser spot form a line???.

Boy the jeffery cell is pretty hard to make ! well close to the original ! i don't think there are many people that can cut that crystal ,how long do you think it will take and are you making a spare ?


It looked simple to start with, I have never done any lapidary stuff before, so am starting from scratch, if I get the thing physically built, I then need to sort out a circuit to test it out, if I achieve success I will send you a crystal, jeffree states a thickness of .010", thats going to be very fragile, that is for his recommended 10mhz, but mine may finish up slower and thicker.

maybe the damper could be a piece of sponge?????????.

i think he wanted to make money from it which is strange as they use micro nano mirrors ? these days anyway to do they same thing 100 times better


True, but we are the sort of people that like to play with bits and bobs for the fun of it?, I did get some stainless and rigged up a coil, it was thinner than the .5mm specified but the line it made was good but at a lower frequency.
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Postby Harry Dalek » Mon Sep 12, 2011 11:58 pm

Hi John

I understand that he was expecting he's invention could make him money and was keeping its workings to him self ,i think they all had enough of him at the end when he would not answer questions put to him .
Yes we like making stuff from junk now and again it works free to view and copy :wink:

Well i was thinking sponge or wood perhaps any thing that reflects the utrasonic wave is not good ..just had me wondering i don't think thats hard ....i hope ... trial and error will work that out .

Thanks ! think a thicker crystal you need amplifying ....i wonder if it would work at double the frequency as your going for 10mhz i think if it would work in the 20's perhaps a simple CB radio would work ? you have the modulating and you have the high RF ...feeding the crystal ...just an idea....unless you have a ham radio transmitter that does 10mhz handy ?

On the HD motors i saw one guy try and run them sort of got it going but they needed a push start so i never really looked more into it ...i was and did at the start use the control board fitted but i was using to much weight for nipkows at the start and the motor aways died after a while ...but for the polygon yes that should be no problem ..i am in the habit of using normal dc motors and rubber bands i am in a rut :wink: but.....am into stepper motors now as well .

Yes the HD platter is a mirror finish ! but if you cut them you have to polish and i am not sure its not just a coating on the platter ..
You could mask off lines around the platter and paint the rest black remove the tape line and have a sort of front reflecting lines need another rotating mask infront of that never know you must have a lot of spare HD platters about in your work shop like me ...one day !!!!!

OH Before i forget i did some experiments on mica not only does if reflect a laser light like a mirror is passes it as well same time it would make an interesting mirror screw if you could get enough of the stuff but i have only seen mica as transistor heat sinks ...in one of my passed posts it was used for light modulation you could double reflect the light via the stuff.
Last edited by Harry Dalek on Tue Sep 13, 2011 12:16 am, edited 5 times in total.
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Postby johnrpm » Tue Sep 13, 2011 1:20 am

OH Before i forget i did some experiments on mica not only does if reflect a laser light like a mirror is passes it as well


Thats interesting Harry, I have some transistor insulators, I shall have a play, as you say they would make a good beam splitter.

EDIT

I tried some mica, and you are right it does pass light and reflect it, I also got the same result from perspex, I think what is happening here is that the material passes light at a high angle of incidence and as the angle is lowered the surface reflects a proportion of the light.

Some food for thought, (pure conjecture), at 90 degrees to the material surface (perpendicular), does all the light pass through the material? (ignoring losses) and at say 45 degrees to the surface do we get a ratio between light reflected and light passing through, is this ratio constant or does it vary with the angle?????, if it varies we have a crude form of mechanical modulation perhaps, but maybe not easy to implement,
perhaps someone with more than my 2 remaining brain cells could answer this.
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Postby Harry Dalek » Tue Sep 13, 2011 11:44 pm

johnrpm wrote:
OH Before i forget i did some experiments on mica not only does if reflect a laser light like a mirror is passes it as well


Thats interesting Harry, I have some transistor insulators, I shall have a play, as you say they would make a good beam splitter.

EDIT

I tried some mica, and you are right it does pass light and reflect it, I also got the same result from perspex, I think what is happening here is that the material passes light at a high angle of incidence and as the angle is lowered the surface reflects a proportion of the light.

Some food for thought, (pure conjecture), at 90 degrees to the material surface (perpendicular), does all the light pass through the material? (ignoring losses) and at say 45 degrees to the surface do we get a ratio between light reflected and light passing through, is this ratio constant or does it vary with the angle?????, if it varies we have a crude form of mechanical modulation perhaps, but maybe not easy to implement,
perhaps someone with more than my 2 remaining brain cells could answer this.



Hi John

The Mica is pretty good i was thinking perhaps just glass would do the same thing did not think of perspex...but mica has one thing over both ...little mass or what we have been using is so thin it has .
A use perhaps in vibrating mirror ideas that needs little mass very much so for the 400hz side of things .
Yes i agree there must be some loss via it but you would not expect it to reflect light as well as it does ..I did not try different angles but if that does change reflected light levels you have another modulation idea for sure .
I like the idea of mechanical modulation which is hardly used now another reason i hope the jeffery cell works out ...thinking about it for nbtv really don't need 10mhz so even it the crystal did 1mhz thats way more than enough for nbtv don't you think ? only really need say 40khz

I have been spending the aftenoon working on the circuit for my dual motor control the LDR circuit is fast so far very happy with it ..tomorrow i hope to finish it off and get that stepper motor going .
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Postby johnrpm » Wed Sep 14, 2011 1:11 am

...thinking about it for nbtv really don't need 10mhz so even it the crystal did 1mhz thats way more than enough for nbtv don't you think ? only really need say 40khz


I have a backup plan if the quartz does not work, a membrane, (not sure what yet) with a piezo spark unit mounted behind, I have removed some of these units and they are made in a stack, I have powered them from a home made unit and they seem to be capable of reasonably high frequency,
so I think I shall be able to achieve NBTV rates, but would like to go higher if possible.

...but mica has one thing over both ...little mass


Yes you are right, ideal for lightweight reflectors, I wish mica had piezo properties????.
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Postby Harry Dalek » Wed Sep 14, 2011 3:07 pm

johnrpm wrote:
...thinking about it for nbtv really don't need 10mhz so even it the crystal did 1mhz thats way more than enough for nbtv don't you think ? only really need say 40khz


I have a backup plan if the quartz does not work, a membrane, (not sure what yet) with a piezo spark unit mounted behind, I have removed some of these units and they are made in a stack, I have powered them from a home made unit and they seem to be capable of reasonably high frequency,
so I think I shall be able to achieve NBTV rates, but would like to go higher if possible.

...but mica has one thing over both ...little mass


Yes you are right, ideal for lightweight reflectors, I wish mica had piezo properties????.


Hi John
Rereading my post on mechanical modulation the experiments via a speaker used Mylar...what by the way are piezo spark units ?

i was going to buy a powerful Piezo but they cost a bit ..ended up just getting a few cheap small ones to try out ...i wanted to see in time same sort of idea but for the deflection if i can move a laser passing water like the first laser projector then i did a homer simpson hang on !!i just need speakers as i would just be amplifying 400 hz not 15750 or 25 ...i don't think they used a wave to modulate on just used the frequency perhaps just a sawtooth ,this i am not sure about ...trial and error if i ever get around to it .

On mica since its thin i would say it would vibrate well have you tried a angle test ,i will try it when i have time .

Hows the cutting going ?
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Postby johnrpm » Wed Sep 14, 2011 6:25 pm

what by the way are piezo spark units ?


Sorry for not explaining very well, here is another area of interest that may show what I mean. http://reprap.org/wiki/Scratchbuilt_Piezo_Printhead
yet another thing to take up time.

Rereading my post on mechanical modulation the experiments

Could you direct me to these please.

On mica since its thin i would say it would vibrate well have you tried a angle test ,i will try it when i have time .

Hows the cutting going ?


I do not get much shed time in the week, only at weekends, and thats only if "she who must be obeyed" does not have some DIY for me to do.
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Postby Harry Dalek » Wed Sep 14, 2011 10:27 pm

Hi John

The Scratchbuilt_Piezo_Printhead looks interesting i was going to ask you about the printer jet thing you were testing in one of your videos is that the same thing ..looked like it worked well i had not heard of them before but had wondered how those things worked.

OH the Stretched Membrane Modulator can be found here aways down the page .

http://www.industrial-electronics.com/laser_13.html

Heres the laser with interesting scan ideas .

My problem is the kids and my shed has gone feral ! but i know what you mean very hard to find time to indulge in the passion but i find ways between this and that.
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Postby Harry Dalek » Sat Sep 17, 2011 10:22 pm

Hi just found i had this patent when it talks about the thin foil between the crystal i was told once closest thing would be the foil in cigarette packets.
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Postby johnrpm » Mon Sep 19, 2011 8:42 am

I have rough cut the first crystal and am half way through the second one, I did a stupid thing (not the first time) and tightened the clamp a bit too hard, and created some internal fractures within the remaining block,(very brittle) so may just get one more crystal out of it, as the block gets smaller it gets harder to hold,
I shall try warm wax to stick it to a holder, but if it fails damage to the crystal is sure to result.

Just a thought, but on one of the images you posted Harry, it shows the cell end at a slope of about 45 degrees, I wonder if this is to disipate the wave energy instead of a virtical end with sponge?????.
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Postby Harry Dalek » Mon Sep 19, 2011 4:54 pm

johnrpm wrote:I have rough cut the first crystal and am half way through the second one, I did a stupid thing (not the first time) and tightened the clamp a bit too hard, and created some internal fractures within the remaining block,(very brittle) so may just get one more crystal out of it, as the block gets smaller it gets harder to hold,
I shall try warm wax to stick it to a holder, but if it fails damage to the crystal is sure to result.

Just a thought, but on one of the images you posted Harry, it shows the cell end at a slope of about 45 degrees, I wonder if this is to disipate the wave energy instead of a virtical end with sponge?????.


Hi john i am keen to see what they look like ,yes its hard to take that risk and these things happen ...no worries least you have something to experiment with in the end .


Yes i bet the smaller it is the harder it is to cut but see how it go's let us know either way .


I can see in a past Scophony system i posted they used this tank in the patent ,i still have to get my head around this tank its got the crystal at the bottom left hand corner this directs the U S waves up off a gagged wall ...where ever the sponge is in this one i am not sure ,i am reading the patent in full and one thing it says using it to modulate tv the light needs to be less than a mm wide lucky we have lasers how they did to back then must of be a nightmare of lenses.\...
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Postby johnrpm » Mon Sep 26, 2011 5:13 am

Not much progress this weekend, I built a crude lapping machine using an old window wiper motor, I looked all over for some cast iron to make the lap with but had to settle for aluminium, the power supply is from an old PC, they can deliver plenty of amps and have 3.3v, 5v, 12v, the green enable wire needs to be tied to negative, I may make a holder for the crystal to oscillate it across the surface as its very boring by hand.
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