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markse68

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Blog Entries posted by markse68

  1. markse68

    Disaster- a wasted day

    By markse68,

    Ballcocks! 😞 Well you learn something new every day and I learnt today that you shouldn’t use aluminium formers to silver solder brass...
    It started off so well as well
     





    Guess I’ll be starting that again from scratch- ballcocks
  3. markse68

    Magnetic coupling

    By markse68,

    Initially I planned to make the focus motor quick release and the magnetic coupling made some sense but I ended up going for a simple screw mounted motor so it makes less sense now 🤔 But it’s done now and it works really well- better than I’d expected. It allows for lateral misalignment yet is a nice stiff rotational coupling for the sort of torque required to turn the moonlite knob. A ptfe pad keeps the magnets slightly separated so the two plates can move a little easier against each other. The black magnet holder on the focus knob is 3D printed and a press fit on the knob


  4. markse68

    It’s alive 2!

    By markse68,

    Finally bit the bullet and knuckled down to wiring the handpiece- really made a rod for my own back though with the very tight space for the wires...it’s going to be really tricky getting the other half of the housing on there without squashing wires 🤦‍♂️
    But it works-almost perfectly-almost that is except the pwm on the LED isn’t pwming 🤔 I swapped from a nano to the new Arduino nano every and I’m guessing the code isn’t totally compatible...

    0E01F364-3061-4211-904D-1334A76EFE8A.MOV
  5. markse68

    Spider hub

    By markse68,

    The spider hub came together tonight- bit of a mare as it’s glued together with high strength retaining compound which gave me about a minute to assemble everything and try to align all the screw holes 😳- needless to say it was a right panic not helped by a friend deciding to strike up conversation at the critical moment. Wish I hadn’t rushed it as it’s not perfectly aligned and not much I can do about it now but it’ll do I think.
    It’s getting a bit hefty though which is a worry- 200g already but that’s all the chunky bits bar the mirror itself. A lot of that is the central 10mm stainless shaft- might think about replacing that with aluminium or at least drilling a bore all the way through.
    the adjuster screws need to be shortened a bit too


  6. markse68
    I had to wait an unbearably long time but the 3D printed housings arrived this week and they look great 👍 Surprisingly everything fits- a bit snug but it fits! I’d hoped to get the handset all soldered up today but wasted too much tome shopping so I’ve just been staring at it- psyching myself up to it and trying to plan the best way to wire it- it’s a tight fit and I don’t want to screw it up. The little round pcb is a reverse polarity protection pcb I built for something else that also used li-ion batteries...which is handy 😉 The battery cap still needs milling.



  7. markse68
    Disappointed with the function of the design yesterday due to friction issues I’ve modified it- it now has only one spring and 4 screws. The spring keeps the indexing screw in contact with the v-groove in the mirror cell top plate. Adjustment is achieved by slackening all the screws then adjusting the tilt to focuser angle with the indexing screw, and the focuser-axial rotation with the 2 side screws then all 4 can be nipped up to lock it which is better than just relying on the springs I think.
    The movement in the video is extreme but shows the arc of the movement around the ball joint and the function of the swash plate. In real life I’m not sure the small adjustments required justify the swash plate really but it at least stops the screws digging into the aluminium.
    It works 😃

    C3A6ABFC-96A1-4C98-82CE-3CDB042F09E6.MOV
  8. markse68

    It kinda works 🤔

    By markse68,

    Completed the screw adjuster plate so I could give the swash plate mechanism a try- it does kinda work but I think there’s too much friction in the swash plate and the ball joint- a ready made Igus part. So I’m thinking they might need to be ptfe and polishing the back of the mirror cell top plate will likely help. But getting there I think...


    40749B06-F1D5-43DB-9E9C-3ACA97EC0561.MOV
  9. markse68

    The design

    By markse68,

    I like the original secondary mount on my Fullerscope- it cleverly separates the tilt from the rotate of the mirror but it’s a bit crude and too big for my new mirror. The new design is meant to be kinematic and I think it is 🤔 It tilts the mirror on a ball joint and axial rotation is locked by a sliding key way on one of the adjuster screws. There are 2 adjuster screws opposed by strong springs and the second screw and the springs bear down on a nylon swash plate to make the action smooth. The nice thing about the ball joint is it puts the point of rotation just behind the centre of the mirror so lateral motion should be reduced. The mirror will be supported around its edge in a brass thin wall tube like the AstroSystems holders.
     Here’s the new mirror- a quartz one from Protostar, and the design of the mount.


  10. markse68
    While I’m waiting for the 3D printed parts for the stepper focuser I’be been making a bit of progress on the secondary mount. Here’s the top plate of the mirror cell with the ball joint and the rotation locking grooved insert and a video to show how it’ll work. You’ll have to imagine the mirror tube as that’s next on the todo list 😉



    69104768-5797-42C4-ACB7-BF8EE2E23CF9.MOV
  12. markse68

    The motor mount

    By markse68,

    Working on the motor mount this evening- needs a bit more work but the general idea's there. I'm going to use a magnetic coupling and am thinking to make it quick release so I can take it off if I don't want to use it.

  13. markse68

    Slight improvement

    By markse68,

    24C2AE88-8FBD-47E7-BD34-716FB9018988.MOV Managed to square up the waveform for the step at the expense of halving it’s max frequency🤦‍♂️ But I’ve changed the driver board for the version that actually has half step input so my new max speed is about 3sec/rev which looks ok I think. It’s slmost working how I want it but I need to figure out how to shape the response as it’s too long in the very slow movement then suddenly shoots off into high speed- not sure why as the step times should be linear from the pot 🤷‍♂️ Needs some thought Mark
    (Hopefully the video will load better this time with different codec)
  14. markse68

    It’s alive!

    By markse68,

    It’s very rewarding to see the motor moving 😊 Few issues though- it’s not a very linear response at all. I have a feeling that I need to make the step pulse train symmetrical high/low and just vary the frequency. The Trinamic driver I’m using has this feature called microplier where it interpolates input steps to output 256 micro steps for each input step (or 2 as that’s minimum input resolution I can chose without using serial interface) Nice feature as it makes the motor really smooth but it relies on reading last step period to calculate internal frequency so I think the fixed short pulse/ varying delay I’ve implemented is screwing its calculations up. Shouldn’t be too hard to convert my signal to a nice symmetrical pulse train though. I’m aiming for 1 revolution per second max speed which is plenty when driving the coarse knob of the Moonlite.
    B213CE42-E334-402E-97BC-9694CE715EF4.MOV
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