(Topic ID: 257530)

Greek Gods Homebrew

By Cmartin1235

1 year ago

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  • 166 posts
  • 25 Pinsiders participating
  • Latest reply 8 days ago by Cmartin1235
  • Topic is favorited by 30 Pinsiders


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    There are 166 posts in this topic. You are on page 4 of 4.
    #151 63 days ago

    I love all the welding you have done on your Trek theme machine! https://pinside.com/pinball/forum/topic/star-trek-discovery-pinball-machine-/page/8

    #152 62 days ago

    Thank you Sir. I am currently geting mixed reviews on making some wireforms for t.n.a. I use flat stock plates with cut outs to weld wireforms together. They just slide down and I put one on each side of weld. These spacers look very interesting to try. I did not know where to get them, so thanks again I have a 3d printer and will print out a few.

    #153 58 days ago

    Next time I weld wireforms I’m going to try to milling copper plates to snuggle up next to the weld junctions. I’ll put one on each side of the weld as you do. That should help limit spill over heat and damage to the rod.

    1 month later
    #154 15 days ago

    Greek Gods burnt out another servo. The ramp diverter flap managed to pinch a ball when changing directions from left to right ramp. It wasn’t supposed to happen since the trigger for the ball switch is lower on the playfield. But it did. A jammed servo struggles against the impossible load and gives up the magic smoke. Time to rethink the diverter.

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    #155 15 days ago

    The problem with a standard servo is that it does not know when to give up. It receives a pulse frequency from the PDLED which it faithfully converts to an angle. If it does not reach the angle it tries harder. Eventually heat is the end of its control circuit or motor. At this point my options are to make my servo smarter or switch to a stepper. If a stepper does not reach its goal it does not give a crap. It executes its 800 micro steps (or whatever) to achieve the desired angle and give a shrug as if to say “I did what you said. 800 steps were conducted.” The worst that happens with a stepper is that it gets out of alignment until told to find its home position with feedback from a micro switch. You might wonder about using coils on the diverter. I’d have to put them under the playfield, right through the middle of a subway. So smarter servo or stepper it is.

    #156 15 days ago

    Looking at the geometry, a servo sure fits better in that place. The shaft of a stepper is in the middle of the motor whereas a servo is offset. While a stepper is probably a more reliable solution, to use it, I would have to either mount the motor above the flap or use a transmission to move the axle.Both possible but a more significant redesign. Instead I think I’ll try to make a smarter servo.

    #157 15 days ago

    from an earlier pic it looks like there is a fair amount of space under there above the playfield, I would certainly try to fit a coil sideways underneath the plastic with a lever arm to pull the diverter to one side and have it spring held the other way. if it happens to jam a ball in there the low power coil designed to be always on would be fine, and have it in your ball search routine if you have one.

    not sure it that makes sense, or if there is really room as its hard to tell from pics. I'm also assuming the diverter is up against the rail at either end so the force of ball hits is taken up by that instead of the servo/coil/stepper.

    #158 14 days ago
    Quoted from Cmartin1235:

    The problem with a standard servo is that it does not know when to give up. It receives a pulse frequency from the PDLED which it faithfully converts to an angle. If it does not reach the angle it tries harder. Eventually heat is the end of its control circuit or motor. At this point my options are to make my servo smarter or switch to a stepper.

    I recently added a feature to MPF to stop a servo. Also works with the PD-LED. This way the servo will stop trying. You could use a timer to implement that event. I demonstrate this in this video (with the pololu maestro but works the same with PD-LED as we tried in the P3-Roc video yesterday):


    #159 14 days ago

    Thank you Jan for the excellent video on servos. I remember us talking online about the disable making its way into MPF. I didn’t notice that it was already there.On my current configuration, the servo is taking the beating of the ball. I’m relying on the metal gearing to hold together. Im realizing that was a mistake. I need to add stops on the ramp for the flap so the servo can bring the flap just shy of the stop and then disable, letting friction hold it in position and the stop to take the beating.

    #160 14 days ago

    On an early version Are used 12v mini coils just blow the ramp flap. It mostly worked but mechanically was not as reliable as the stepper I replaced it with. The steppe went away when I re-designed the orbit for lack of space. Real coils would be a more robust solution but there is not quite enough room for me too put a coil and the requisite transmission to control that flap. I believe I have worked out a way to detect ball jams. Rather than put a switch on each flap position, I will try putting one in the middle. When a ball gets pinched, the flap can’t make its full excursion and I should be able to detect a prolonged “middle” switch activation and reverse the servo.

    #161 14 days ago

    A mechanical switch and cam is turning out not to be as reliable as what I expect to get out of this Opto interrupter. I bought a few of these thinking I could use them on spinners but the gap wasn’t quite wide enough to make it work. Lucky for me I kept them and it should be perfect for this.

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    #162 13 days ago

    Here’s a list of all the things I’m doing to mitigate a marginal diverter flap design:
    1: Put a fuse on the servo. My reading says that the servo should draw about 300 mA when moving and draws about 2 A when jammed. I’m putting a 1A fuse on the power line. 2: my replacement servo is a digital servo that allows me to program a power reduction when jammed. So far the drivers have failed to load properly under windows 10. If I can get this figured out I will program a step down in power when jammed to be a backup to the fuse. 3. After stops are welded in, l’ll deactivate the servo after the flap position is reached or a timer has expired. 4. Use the middle position optical gap switch (above) to detect movement of the diverter flap. If the switch stays active more than 500 ms, reverse the direction and try again. 5. Make the servo easier to swap out so if it fails at a show I will be able to do a 30 minute repair/calibration to have the machine running again.

    #163 13 days ago

    I am wired up and the switch is working. Now for a little calibration and testing.

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    #164 11 days ago

    In MPF dev I also added a servo timeout which can be configured per servo. That might also help.


    #165 10 days ago

    Why not add a spring between diverter flap and the servo? In the case it is jammed, the servo will run to the end position and the spring just expands. This will also protect the servo gearing against ball slamming into the diverter

    #166 8 days ago

    That’s a good idea. The servo would still be working against the spring but not with nearly the force of it grinding against a steel ball. Maybe I could mill something out of aluminum to hold the spring(s). It would be an interesting fix. Thank you.

    There are 166 posts in this topic. You are on page 4 of 4.

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