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Thread: Remote remote control - how to press the buttons?

  1. Remote remote control - how to press the buttons?

    Hey guys!

    I'm trying to do a "remote remote control", a robotic finger pressing buttons similar to what you have on a tv remote. The buttons are made silicone and the actuators under them are likely the rubber dome kind, something like this:
    Click image for larger version. 

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    The design of the buttons are such where to make the button actuate you have to press the button slightly below the plastic frame surrounding (on the previous picture there's no frame, only the silicone) the button itself.

    My finger looks like this:
    Click image for larger version. 

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    I 3D printed this cone-shaped finger which I attached to a servo. This has actually 2 parts: the finger itself is a mushroom shaped piece, and the part which is connected directly to the servo is a piece of 3D printed plastic which is L shaped and has a hole in the middle. You put through the finger the hole locking the spring between the finger and the connector, so when I press the button I have a bit of dampening so I don't hurt either the 3d printed parts or the buttons of the remote. On the other side of the connector you just put through a screw on the hole I have on the finger so you can make sure it won't fall out while operating.

    Now my problem is: because of all the rubber/silicone on the remote, the finger is required to press the button in a certain angle which I can't really record (I use the AX-12A servos) because the buttons are so small that when I record there's always a small error in the recordings, I have to manually edit the recorded positions to replay how the buttons are supposed to be pressed. With a human finger it's easy to do because it bends in a way that you cover the whole rubber dome underneath and the applied force will be distributed in a way that it always actuates. My plastic finger however can't do this.

    Because of this, I thought to have a certain "calibrated position", I move the finger always to this position before pressing a button if I have to press 2 different buttons (eg. you want to switch to channel 12), but I just lift the finger and press the button again when I have the same buttons (eg. 11). The finger however misses a button every now and then if the case is the latter. I just spent 3 days trying to edit the config a tenth of a degree at a time, and I managed to minimize misalignment errors (eg. using zip tie and a spring with the servos so the backlash is dampened), but sometimes I suspect the finger slips a little bit when it presses the same button twice and gets misaligned, misses the second button press. I could potentially reset the position so every time it goes back to that instead of just lifting the finger when it's the same button, but that'd drastically slow the process if I want to quickly switch a lot of channels (eg. just surf through with the "next channel" button)

    I tried to print a different shape (hence the different colors on the pictures) where the finger contacts the button so I tried to maximize the surface where I apply the force, but I still have a significant amount of errors. I can't increase the contact surface because unlimited amounts because the point of actuation is below the plastic frame, and if the finger can't go below the level of the plastic frame, the button won't actuate.

    The solution works with mechanic buttons or scissor switches (I tried it on a mechanic switch tester and a laptop keyboard), it's only the rubber domes which are problematic, but I'm not even sure if my approach is not totally flawed because remotes are traditionally not made with mech switches :DD

    The room between the hole in the connector and the finger is so minimal that the finger can almost only rotate but not move around in the connector.

    Ps: I'm not expert on robotics, so any piece of advice would be welcome! :)

  2. #2
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    Re: Remote remote control - how to press the buttons?

    Since you are already fixing the position of the remote relative to the servos, why not just print a small overlay that fits each button and creates a larger solid area above the top surface of the remote for the finger to press against. Instead of trying desperately to press the small rubber button below the top surface of the remote, you instead use use the servo finger to press a hard button/spacer that presses the soft button of the remote to make it behave more like a nicer mechanical switch.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

  3. Re: Remote remote control - how to press the buttons?

    Quote Originally Posted by tician View Post
    you instead use use the servo finger to press a hard button/spacer that presses the soft button of the remote to make it behave more like a nicer mechanical switch.
    assuming that I have different kinds of remotes (of which some comes without assembly specs to tell me eg. how distant the buttons are from each other), how would you approach designing such a spacer? trial&error?

    I'm trying to understand if it's even worth it to try fixing the error itself, or make countermeasures in case an error happens (eg. mixing vision to the solution?)

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    Re: Remote remote control - how to press the buttons?

    Depends what tools you have at your disposal to measure the remote. A simple ruler would be cheapest to make a simple estimate of each button's size and position on the remote, then use those measurements to create the remote holder with a grid of holes centered over each button. In each hole you place a plunger/pin with small cross-sectional area to push the button below the remote's plastic surface and on each plunger/pin you place a cap with a larger cross-sectional area to enable the finger to press it without requiring as much precision as directly pressing the rubber button.

    Easiest method would probably be taking a picture of the remote with a reference like a ruler/grid and importing it into a CAD program, then scaling that reference image to match the CAD grid size. Once that is done, you just draw over the image to create the remote holder and the grid of holes for the plungers/pins. The thickness of the remote holder should be at least twice as thick as the width of the plungers/pins to prevent them rotating out of their translational axis that should be perpendicular to the rubber button's surface. That will ensure the plunger/pin actually presses the button straight down regardless of where the finger presses on the cap (press the edge of the cap and it still presses the button correctly).

    Since creating the remote holder and plunger/pin grid would give you the positions of each plunger/pin on the remote holder surface, you could abandon the manual programming of each button and just use a bit of math to determine the servo angles required to put the finger over each button.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

  5. Re: Remote remote control - how to press the buttons?

    thanks for the tips! I already imported the picture to Fusion360 as you suggested to have a reference, I'll go with the infamous FDD approach (f*-up driven development :DD), and try to get the spacer work.

    just out of curiosity, how would you take a picture so the grid isn't distorted? eg. if your angle is slightly off from directly above you won't be able to properly scale the reference to your grid (without some editing) right? Are there any software on the market which tries to help you with this transformation? I took a bunch of pictures and tried to select the best, but I wanted to see if there's a way agreed upon in the industry to take such pictures :)

    cheers!

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