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Thread: Barróg - Featherweight Lifter Build Diary

  1. #21
    Shooty's Avatar
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    Eoin
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    Huzzah, visible progress! So over the weekend I was finally able to start cutting some of the HDPE strips, and have made progress on the sides, back plate, base, and lifter face. I still have to round out the back of the side plates, and see if I can shrink the design further, but it's something.









    I have also finally been able to order speed controllers for the damn thing, and will hopefully get the wheels soon, which should be the final part to get. I'm still a little iffy on the actuator controller though. Microswitches seem compact, but it doesn't look like I could stop a linear actuator halfway with them, which may be a worry If I'm say, clamping down on another robot, and am a little worried that I might do damage to something inside the machine. a speed controller seems like it would give me that functionality, and if I were to go down the ESC route, would the Botbitz 30A controllers be a bit overkill? I'm asking because they are what I'm using for the drive, and since I'm only just ordering them today, it would be convenient to send everything in the one package. If they are overkill, could I find another speed controller that could take the 18.8V outputted by the battery?

  2. #22
    R9000's Avatar
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    Rory Charlesworth
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    You're using 30A for the drive? Is that four individual controllers? As for the actuator, I don't know what kind of current it's pulling, but it shouldn't be a huge amount. I should think a 30A would be ok, but there might be a better option. If you have a ammeter with a decent capacity, you could try putting the actuator under load and seeing how much current it draws straight from the battery. Otherwise Jamie's point here: http://www.fightingrobots.co.uk/thre...l=1#post468452 is an excellent solution, and would allow you to stop the actuator halfway.

    Also you weren't kidding. This machine is immense.

  3. #23
    Shooty's Avatar
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    Yeah, it certainly is big. It's a side effect of the mounting of the actuator, if I ever make a Barróg 2, then it will almost certainly use a high torque motor system instead. I'm hopeful I can reduce the weight enough though while also keeping it at least somewhat sturdy. ALso I'm planning to run each sides motors in parallel, so an ESC will be shared on each side.

    I'm not completely certain that my readings were accurate, but I measured the current draw of the LA with a multimeter, and I found it drew roughly 1.7-1.8A when in use, bursting to roughly 2.5-3A at the start of the connection. That sounds right to me considering that the no load current of the LA is .85A, and it's being overvolted. It certainly seems 30A is a little excessive: the issue for me though is if a brushed speed controller exists that A) is more cost efficient then the Botbitz ESC B) can take the 18.8V provided by the LA and C) can still take the current drawn by the LA.

    If Jamie's solution can do the job though, then that'd be excellent, I have a few servos left over from my antweights that would do the job.

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