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Question Sabertooth 2x32 & Uno Rev3

Discussion in 'Electronic and hardware generally' started by Deane, Sep 7, 2018.

  1. Deane

    Deane Old Fart

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    I am still struggling with the electronics on my 2DOF build.
    My motors arrived and know I need to order the brains of the system.

    So I have decided that a Sabertooth 2x32 Controller will best suit my motors which are the 50:1 versions of https://www.motiondynamics.com.au/worm-drive-motor-12v-24v-200w-180-rpm-20nm-torque.html
    but I am a little confused as to why it recommends using a battery in parallel with an suitable size power supply such as a Meanwell or an couple of HP Server power supplies.

    Is that correct or did I misinterpret the whole thing ?
    The other part that I know I must use with the Sabertooth is an Arduino Uno Rev 3 but again I see that there are many different versions or knock- offs at half the price and a developers Uno Rev 3.
    So am I on the right track with this one https://www.littlebirdelectronics.com.au/arduino-uno-r3 please ?

    Electrickery. Give me a welder anyday :sos:sos:sos
  2. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    The Sabertooth 2x32 can be used with a PSU, but the 2x60 needs batteries to deal with regenerative current:

    [​IMG]
  3. Deane

    Deane Old Fart

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    So presumably the two PSU's that I ordered from Fleabay which are 12V 30A 360W should do the trick.

    After some more reading of build threads and people's bad luck with pot's durability I am opting for the Hall Sensor method and ordered some of the same SENSOR HALL 0.2V +20V TO -10V PIN - 6127V1A180L.5FS (Fnl) :eek:
  4. FoxHound.92

    FoxHound.92 2DOF seat mover Gold Contributor

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    Has anyone already used clamp resistors instead of a paralell battery with the sabertooth? Or does the sabertooth 2x32 not need a battery?
  5. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    As per the description for the 2x32 you do not need to use a battery to deal with regenerative current.
    • Agree Agree x 1
  6. FoxHound.92

    FoxHound.92 2DOF seat mover Gold Contributor

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    That's what I made of it. Was double checking because it is also stated at least one should be used.
  7. Peacemaker105

    Peacemaker105 Active Member Gold Contributor

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    My question is, are the supplied 10w, 5 ohm resistors supplied big enough to handle max working load? my electrical knowledge is limited in this area. I bought 100w 1 ohm ones off ebay before i realised they supplied some in the box haha. I have 24v 450w motors. I was just going to use what came in the box but the picture above shows them doubling up on each side with extra resistors.. so 4 per 2x32 instead of 2 which is supplied or would my 100w 1 ohm ones work better/safer? 10w per channel doesnt sound big enough for the power i'll be runnning, but then again i dont fully understand how they work, maybe 10w is enough to save your PSU?
  8. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    See the resistor calculator here: https://www.dimensionengineering.com/calculators/power-resistor

    And the Sabertooth manual here: https://www.dimensionengineering.com/datasheets/Sabertooth2x32.pdf
    Last edited: Nov 17, 2018
  9. Peacemaker105

    Peacemaker105 Active Member Gold Contributor

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  10. ilbiga

    ilbiga Active Member

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  11. Pino Pistolidas

    Pino Pistolidas New Member Gold Contributor

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    I also had some difficulties understanding which resistors to use. I contacted Dimmension Engineering and as I understand it know:

    You are using 450W motors at 24 volts which comes to 18.75A
    The maximum current de Sabertooth 2x32 can disapate is 8A, so this is the value you have to use in your case.
    So 8A x 24V = 192W which you can disapate per side (P1 and P2) so in total 384W, please correct me if I'm wrong.
    And the resistor you would need per side is 24V / 8A = 3 Ohms which can handle at least the 192W so lets say 200W.

    The 200W resistors are expensive and not so available. So you can either use 2 x 1.5 Ohms 100W reistors in series per side.
    Or 2 x 6 Ohms 100W in parallel per side.

    The last one is also what I'm going to try I ordered 4 of the 6 Ohms 100W resistors from Aliexpress, which will arrive next week.
  12. Milani Fabio

    Milani Fabio Active Member

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    Hi Pino and Peacemaker105,
    I also asked this question and I also found the same answer.
    I have 3 24v and 350w engines and with the calculator I also get a resistance of 3 ohom and 192 w for each motor.
    I bought this aluminum resistance of 3 ohms and 100w, but nobody told me ok, let's hope it's enough.
    images4PQSBGJE.jpg
    I've seen photos of other systems, but with resistances of 1 ohom 10w ..... and I've never seen 192w resistors ..... bohhh!
    Perhaps the regenerated energy never reaches a maximum of 192w and therefore a lower resistance is also sufficient.

    I understood that all the answers are already written in various posts, so you have to read a lot, but to my great regret when you ask for a specific thing or a confirmation it is difficult to get an answer.

    Hello
    Fabio
  13. Pino Pistolidas

    Pino Pistolidas New Member Gold Contributor

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    Hello Fabio,

    I received my resistors last week and connected them to my Sabertooth 2x32. They do help but not as much as I hoped.
    My power supply is still tripping.
    What I also noticed is that on connection P2 more power is disapated than on P1?
    I checked this by measuring the voltage over the 3 ohms resistance while I had SMC3 generate Square waves.
    Didn't matter if Motor 1 or 2 was running.
    I haven't found out why yet.

    I'm wondering if this is the same for you?

    Also my resistors aren't getting warm at all, probably this is because they aren't in use constantly. So mayby your 100w versions will survive.
  14. Milani Fabio

    Milani Fabio Active Member

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    I don't know, I'm still in the editing phase, I haven't tried anything yet ….
    • Like Like x 1
  15. ilbiga

    ilbiga Active Member

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    Benvenuto ad un altro italiano!:thumbs

    Welcome to another Italian! :thumbs
  16. bixler13

    bixler13 Member

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    I just finished a build with the sabertooth 2x32. I think your solution is to run a bridge rectifier.

    I initially ran it without the power resistors and had no issues with my power supplies tripping, likely because I had the bridge rectifier in place. After running for a bit I added power resistors to see if it would cool the temp of the bridge rectifier, but it didn't. The power resistors stayed cool to the touch, so i'm not even sure if they contribute much.

    More info can be found here about the bridge rectifiers.

    I am using one of these (50a 1000v) bridge rectifiers for both of my power supplies, although I might move to running two in parallel or wiring the rectifier up so that the current capacity is doubled due to the heat these things generate in use.
  17. Milani Fabio

    Milani Fabio Active Member

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    • Agree Agree x 1
  18. Milani Fabio

    Milani Fabio Active Member

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    I have just arrived ... here they are!
    20190329_103202.jpg