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Gregory wrote:Harry, yes I will be using 4046 together with a ripple counter for the frequency multipliers. Unfortunately my mirror/motor combination for the line scan is not ideal as the multiplier factor is non integer, and will lead to slight complications, But there's no choice available, polygon mirrors are hard to find. Perhaps a new post on ways to construct a custom polygon mirror would be useful.
Well easy to construct badly ! to make something to match a laser printer polygon octagon or what ever your 12 sided mirror is called is very hard ,more so the motor mounting correctly true ...this wobbles your mirror it will work but you get a wobble in the raster ...need something like a video head or HD motor no wobble with them .
There's a bit on the old newsletters via Allan Short years back use to make them but from what i saw be nothing like what you could do with your CNC machine these days...you made the frame drum that's pretty good !
What mirror number of sides are you looking at thinking about making .
Gregory wrote: I think a better way of doing this maybe to have some sort of jig to hold the mirror faces accurately and then glue the mirror mount to the mirrors.
Harry Dalek wrote:An accurate Temp mount say 16 sides but do not glue back at all they will all be off no matter how little you use all faces will reflect different ! i learnt that mistake the hard way got to fix it flat to the mount your screw mount idea is good ,if you can stay away from glue its the way to go .
I suppose you could redo the frame drum to fit what you have made as is ?
Gregory wrote:On second thoughts, yes I think your right, best to keep with the screw mount idea, The frame mirror is OK for the moment and quite accurate as I had this already built, but it would be good to modify & improve this further, so it could be used for the line scan mirror which requires a much higher RPM. This may be of interest for other members wanting to use mirror drums for scanning, as polygon mirrors are very hard to get.
For 60 lines / 750hz
15 segment mirror = 3000 rpm
18 segment mirror = 2500 rpm
24 segment mirror = 1875 rpm
Both 7.5 and 1.8 degree motors with low resistance windings, can reach 3000 RPM reliably under light load conditions.
Getting back to the electronics I have started building the missing pulse restorer & hopefully should have this working the following week.
Harry Dalek wrote:Let us know how you go fingers crossed not that you need it
Gregory wrote:Harry Dalek wrote:Let us know how you go fingers crossed not that you need it
No, I think I'll need all the finger crossing I can get.
I have done a few calculations on different mirror/frequency multiplier combinations as below:
FREQUENCY MULTIPLIER divider requirements for 48 step motor
Micro-steps per rev = 48 x 16 =768 (for divide by 16 micro steps)
For 8 sided mirror, Divider = 96:1
For 16 sided mirror, Divider = 48:1
For 24 sided mirror, Divider = 32:1
For the 15 sided mirror I have for the line scan it requires a frequency multiplication of 51.2, which is non integer. This will require a higher frequency multiplier of 256:1 and then separate frequency dividing on the pulse input of the stepper motor of 1:5 to obtain the 51.2 (256/5) frequency multiplication required.
FREQUENCY MULTIPLIER divider requirements for 200 step motor
Micro-steps per rev = 200 x 16 =3200 (for divide by 16 micro steps)
Divider for PLL = 3200 :1
For 8 sided mirror, Divider = 400:1
For 16 sided mirror, Divider = 200:1
For 20 sided mirror, Divider = 160:1
For 25 sided mirror, Divider = 128:1
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