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Thinking about my Octagon

PostPosted: Wed Jul 11, 2012 9:21 pm
by Harry Dalek
Some thoughts on the future project.

A while back i scrapped a laser printer and it had a very nice 8 sided polygon
mirror ..being 8 sided so i suppose its really an Octagon.

I would like to use this in a televisor project ,from a quick test i think i can control it via a clock circuit .

I suppose the circuit that controls the motor has hall effect sensors and such so doing away with a encoder my end anyway .

So i think it will run true to the clock frequency fed to the circuit and or perhaps some voltage adjustment as with what we have to do every time me make the club circuit and adjust it to the motor used ....perhaps.

The neatest way not the only way to do the other scan is to use another rotating mirror can either go laser projection or direct view off the other mirror like a mirror screw ..since i am still at the thinking stage about this i am not sure which way i will go once i get around to it.

I do like the easier direct view since the luxeons easier to modulate for me anyway and i like i get a black and white image and a bit safer than bouncing a laser off mirrors...when i made this quick polygon mirror drum
all i had to do was point the luxeon at the mirrors no optics needed .

you can see the eye of the world and NBTV test cards in that quick video.

I would also like to do a better multi system televisor last one had to much wobble at 60 lines to be useful.

Since that should be no problem for a laser polygon mirror that side of it should be better ...for a 8 sided mirror we are talking i think 3000rpm for 32 line around 6000rpm for 60 line ...i think these things can run from 5000 to 10000rpm .

What this one can do i will find out in time...

PostPosted: Fri Jul 13, 2012 12:32 am
by Harry Dalek
Had a hankering to see if i could drive this 8 sided baby .
So put together this 555 clock with frequency and width control and tested a few caps to see what it likes sure works have nice speed control ..still not sure just got it working .........test today but looks mighty fast .

Think i will make it small i like small so i will look for a stepper and some sort of 4 sided mirror for the nbtv horizontal see if i can get it all going on this pcb board .

PostPosted: Mon Jul 16, 2012 1:14 am
by Harry Dalek
I finished my stepper motor circuit which drives a 4 sided mirror just been playing around pointing a luxeon pen torch at my mirrors .

The line size is the size of the face one of the polygon mirror sides .

So not large but any case looks like its doing the job.

When i have time again i will build a modulation circuit and sync detection which should sync my clock which runs the polygon.

PostPosted: Fri Jul 20, 2012 1:15 pm
by Harry Dalek
I have made up my mind about which way i will go with this little off shoot project ,thinking about it and having a spare UV Laser .......

I am going to combine 2 previous ideas into this one or try so if i fail at least i will give it a good go.

Ones very close to what this looks like now and have done 2 versions of it one with mirrors motor the other used hard drive voice coil .

The second one i have been toying with in my mind for some time is to get back to using UV lasers and phosphorescent screens...trying this a few different ways in the Past SSTV project i sort of know which way to go.

I know the amount of time the laser charges the screen will determine the result on the screen perhaps there will be a lot of ghosting happening ...i am curious to see if you can balance the charging of the screen to over write the past frame.
This is not a Fax or SSTV idea so the charging over writing will have to be very quick ...but i am not so worried about that more if theres enough laser light to do it ,i suppose i could balance the rasters light level to the lasers by dropping projection size ,should show if a phosphorescent paint screen can act like a phosphor used in charged by electrons and the paint screen by photons at UV frequency .

I have a stand alone PWM unit for my NBTV projects for testing ....last night i converted it to modulate run UV lasers a red laser driver as is will not drive a UV laser at all playing around i have worked out a simple way to do it seems to work much better than what i have tried before..i will draw up a schematic when i have time .

The screen is one i had made a while back glass from a a picture frame painted with glow paint on one side .

The laser i am using i need to work out a lens for it it didn't come with a usable one for this project .

Let you all know how it go's...

PostPosted: Tue Jul 24, 2012 8:19 pm
by Harry Dalek
Been a bit slack taking photos so i will get around to it ...i have finished the thing really and been testing .

I still need to work on the laser modulation side i was thinking i had got it right since it transmits the nbtv to my head amp as a receiver but i can see when using it it doesn't switch off enough so with no signal its on and just a bit brighter when modulating ....did a strobe test i can see instead of on off its on and brighter on the strobe bars .

On the testing of the raster screen i tried the phosphorescent screen and just white paper have to say the white paper wins out ,the phosphorescent screen works but its much duller...more than likely due to the lasers power.

Something i was not expecting there seems to be more lines per 4 sided mirror rotation due to the surface area of the large mirrors i am using a few frames per mirror side by side i think .

Dropping the speeds for less lines theres gaps between the lines and you have to move the screen closer to the mirrors or drop the size of your raster to get the lines closer.

Really have to get the transistor to switch this laser correctly so back to testing ,but interesting working on these polygons not only could it be a monitor but a flying spot camera off an object only (not good for the eyes being laser scanned :shock: ) with just a head amp and the light levels are wonderful ...something to play around with later.

PostPosted: Wed Jul 25, 2012 8:26 pm
by Harry Dalek
Ok i had time today to hook it up and take some shots...I have never had much luck on the laser modulating side ..but i know it is modulating but it must be a percentage as i had said before it is on with no signal and just a bit brighter on modulating .

The laser i am using might have a circuit board to protect it so i am not sure this might be effecting filtering the thing ,i do have other lasers so i might swap to see.

But any way here are some photos and videos of it working ...might even do video one day :wink:

PostPosted: Fri Jul 27, 2012 12:21 am
by Harry Dalek
The day has come !

After a few years on and off trying i have worked it out .

Anyone trying to use a laser by pass the diode laser protection circuit....arrrrrr

I swapped lasers today to try this i have not worked out how to get into the can of the UV one i showed you before ....but my red laser is an open type .

Now all i did was solder the wires direct to the laser and that has got it to work ,its not as powerful as my uv its only i think a 1 mw just enough to work.

The photos and video today i have no sync yet but tried my best before my camera needed recharging to take lets see if i can improve it .

PostPosted: Fri Jul 27, 2012 1:02 pm
by Harry Dalek
Thinking what i want to do i know it will work.

I have this old wooden paint box case and i am going to try and case it all in this the biggest problem was the second mirror drum size so i have dropped the size of this as you see ...

The plan is as you open the case the 2 mirror system will be side ways as is for TeKaDe system both mirror motors will be on a hinge plate ...up righting it for normal NBTV system ...the back in side lid of the case will be the projection screen or part of it ..

I am not sure if the first part will work for the projecting but it would be nice if it does and i will see as i go ..the nbtv part is no problem i have to hinge it anyway so it folds up and fits when i close the case lid.

Screen size is better closer or at least adjustable so i will look it to this but again i am limited due to room it would be good to have the drums move in and out to adjust the screen size.

The other problem is the power supply might use power pack but worry about this part later just see if i can case the 2 boards and the mirrors and motors for now.

PostPosted: Sat Jul 28, 2012 7:17 pm
by Harry Dalek
Working out the placement of the boards and and such looks like i am stuck with NBTV format unless i just tip the monitor on the side ran out room to do any thing to fancy hight of the box space was the real killer.

I changed the stepper motor for a smaller flatter type bipolar means i need to solder in a different driver ic but i was just looking at my old one the unipolar and it fits due to the hinge idea so i think i will swap back and save me some work..

Oh don't tell my son where that lego block went !


Just an update while testing the laser i have the 4 sided mirror a little to far from the 8 sided one i forgot about size to distance with these things getting half screen so i will see if i can place the 4 sided one where the laser is and see if i can shoot the beam to and still fill that lid area.

PostPosted: Sun Jul 29, 2012 3:42 pm
by Harry Dalek
I swapped the stepper motors back and placed it where the laser was ,the laser now shoots under the 4 sided mirror to the 8 sided testing seems to work well .
For the time being i am just hot gluing the laser in place to test the modulation out with the uv one in time .
This change gives a pretty large screen about 20cm a screen closer to the laser drops the size and increase the brightness of the laser raster.
Today just working out a little control panel for the motors.

PostPosted: Tue Jul 31, 2012 9:23 pm
by Harry Dalek
The motor control board is now hooked up to my little control panel so i can now control the motor speed from that and still have fine adjustment via the trimmer if need be ...but i think it just needs to be set and left alone.
My laser modulator is using PWM if you are wondering .
I have another circuit for some thing different for sync detection a lm567 tone decoder i am trying ...i hope it will run the Octagon in sync with the sync pulse so i will either try syncing the timer clock that runs that motor or it could just use its pulse ...i am not really sure of the workings of these laser polygon motors but from the test i did the other night its speed is pretty good for manual control must have hall effect sensors adjusting the speed of the thing to the the clock pulse feeding it ...if so it would be nice not to have to worry about that part .
We will see if not back to a tiny encoder paste on !
The 4 sided mirror speed control is not really a problem just adjusts frames your viewing, it would be nice to have it all automatic but one problem at a time.

PostPosted: Thu Aug 02, 2012 6:17 pm
by Harry Dalek
Did a bit of speed testing last night and i found it can do 48 and 60 line no problems if there were 90 lines i am sure it could do that the Octagon looks to be doing 60 line at half the motors top speed seems the only problem with a system like this is the amount of laser light you have ..

A another redesign of the 4 sided mirror in fact 2 i could not help my self when i found a polished 4 sided metal mirror a door stopper had a mirror finish but i found results its no where as good a as real mirror close but i found a slight distortion of the raster dot at either end of the scan so i dumped that idea .

When i got the door stopper i found also some marked down balsa wood blocks just right size so i cut some plastic mirrors to size . and am using that at the moment i find the plastic mirrors better than the glass apart from they can be scratched .

I redesigned back to how i wanted it so i could use the adjustable laser mount .

I am going to try this laser diode tonight got a bit more mW than the red one ...very close to the first one i tried but its just the diode so i can modulate it .

PostPosted: Fri Aug 03, 2012 1:01 am
by Harry Dalek
Got my uv laser to modulate tonight...

Heres a video of a test its not great on shades of grey so shapes letters and such come out ok .

I had it to large its well over my projection screen lid...

I can make it brighter but it washes out the video...need to drop the raster size .

PostPosted: Fri Aug 03, 2012 1:58 am
by aussie_bloke
Looking good!!! :D looking good!!! :D

PostPosted: Fri Aug 03, 2012 9:11 pm
by Harry Dalek
aussie_bloke wrote:Looking good!!! :D looking good!!! :D

Thanks Troy :wink:

Playing around with the second motors mirror size distance such from the line mirror really changes screen size ,i should just project to a wall and see before i drop it .

Really needs syncing seems harder than my other 2 motor monitor trys could be because the 8 sided mirror is rotating twice the speed of my last one .

Also need more control of the video levels all i am adjusting at the moment is the voltage to the laser diode...

Play around a bit more and see what i can do .[/code]