How to hook up my radians to my MK's GR24??

Discussion in '3 Axis Gimbal' started by Ben Freedman, Jan 26, 2013.

  1. Ben Freedman

    Ben Freedman Member

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    Howdy...

    I am using a single GR24 to fly my new C8. Everything seems to be fine.

    I'd like to use the SAME GR24 to control my radians on the gimbal, however, I believe the SUM0 PPM Channel only goes out port 8 on the GR24... So, since that is going to the MK, how do I get another PPM signal down to the radians? Can I use a Y-splitter? Or is there a way to use a 2nd port on the GR24? Or do I need to daisy chain from somewhere else on the MK board?

    Thanks for your help! Reading here has certainly made things easier for me!

    Ben
     
  2. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Hi Ben:
    I'm pretty sure you could use a Y-splitter, but I suspect others on the forum can confirm this.

    I did a Google search:
    can you use a y-cable on servos​

    ...and there are lots of hits that suggest that this is feasible. I can't imagine a Radian sensor presents a larger load than a servo.

    Personally, I'd just try it....I was actually thinking of trying it for exactly the same reasons, but I don't have the time right now.

    Andy.
     
  3. Ben Freedman

    Ben Freedman Member

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    Hi, Andy...

    Thanks for the reply. I will try it.

    Once question.... Would you anticipate any issues coming from the fact that there would now be 1 battery driving the Heli and the GR24, and another battery driving the the Radian Servos (a separate 3S 1300mAh with BEC), and they are now 'sort of' connected through the radians and the servos?

    Ben
     
  4. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Hmm. I'd be concerned that you don't indirectly connect the two batteries up in opposition to each other as the voltages will be different.
    You could isolate the +ve side of the circuit by pulling out the pins for the red wires but making sure that you have a common ground between the two batteries.

    For example, on the servo cable from the GR24 to the first Radian, pull the red pin out of the housing and tape it back. That way the GR24 will not be provide the +ve voltage to the Radians. All of the Radian's +ve and ground pins are interconnected, so you can provide +ve and ground in or out from all the ports.

    If in doubt post a diagram of what you intend to do and the smart guys on this forum will look at it. I'll also look at it too. :)

    Andy.
     
  5. Ben Freedman

    Ben Freedman Member

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    OK, so I'm going to try this tomorrow... Split the 8-channel Sum PPM from the GR-24, and send 1 to the FlightCntl (with power) and send the other to the first Radian (with Gnd and PPM, no PWR)... Sound right?

    Ben
     
  6. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Yeah. That's what I'd try. The common ground is a must, but you have to avoid the +ve from each battery being connected.
    Don't hesitate to post a hand-drawn wiring diagram and let others have a look at it. I don't want the smoke to come out of the wires...

    Andy.
     
  7. Ben Freedman

    Ben Freedman Member

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    Keep in mind that the voltage from the GR is coming not directly from the main Lipo, but through the MK's BEC circuit, and the 12v Lipo on the Raidians is first going through a Castle BEC to get it to 5V.

    Would that mitigate the risk of cross-charging the batteries?

    Ben
     
  8. Ben Freedman

    Ben Freedman Member

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    Howdy...

    So, I tried the Y-connector... Here's what I found..

    If I switch on the MK by itself, it will NOT see the receiver, until I power up the radians. Once I apply battery to the Radians, the MK sees the receiver. At this point, everything seems to work well...

    If I pull the battery from the gimble, again the MK will not see the receiver, and starts beeping.

    My worry is that if, for some reason, the Gimble battery runs out during flight, it appears though the MK will also lose it's connection to the receiver, regardless of the condition of the main LiPo..

    Any thoughts on this? Also, would a 2nd receiver bound to the same TX (MX20) solve this issue once and for all? And would a GR12 be sufficient for this?

    Thanks!

    Best,

    Ben
     
  9. Gary Haynes

    Gary Haynes Administrator
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  10. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Ben:
    What you're describing suggests that the GR Rx is being powered (or getting it's ground connection) via the Radians and the gimbal battery. I don't think that's a good idea at all -- and I think you think the same thing.

    I suspect that there's a wiring error. The MK Boards have to detect the Rx without the Radians being powered up, so I'd disconnect the RX/Radian connection and diagnose the problem without the Radians in-circuit.

    Andy.
     
  11. Ben Freedman

    Ben Freedman Member

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    Hi, Andy.

    If I disconnect the Radians, everything works fine. The MK system without the radians works just fine, and everything is good.

    Per your suggestion, I have removed the RED wire from the Radian side of the y-cable.

    When I plug in the Radian Y-cable (but not the Radian LiPo), and connect the MK Lipo, it still powers up, and the RX still powers up. The RX still binds with the TX, too. But the MK does not seem to recognize the RX. It's like the PPM Servo cable (sumed to port 8) is not connected...

    So we know the RX is getting power from the MK board, because it powers up before the Radian LiPo is connected.

    Then, when I add the Radian LiPo to the system, the receiver is suddenly recognized by the MK, and all is well...

    Thoughts?

    Best,

    Ben
     
  12. Gary Haynes

    Gary Haynes Administrator
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    Ben can you shoot a picture and attach it of your wiring setup?
     
  13. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Yeah....what Gary says. :)
    How do you have the connection from the RX to the FC board for +ve, PPM, and Gnd?

    Andy.
     
  14. Ben Freedman

    Ben Freedman Member

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    Howdy... I can shoot you a picture tomorrow...

    The RX is attached via Port 8 (sum) to the Flight Controller as per your DVD, Andy...

    Let me ask this, Andy... I can't be the first one with this setu.. How do most single-operators with Radians on their 2-axis run their systems? What is the 'best-practices' answer? Is it 2 receivers for completely separate systems...

    Gary... I appreciate your link to that post. Not sure exactly what I was supposed to take away from it, thought? 2 RX is bad? Or just 2 RX with telemetry? Can you enlighten me? Sorry to be a neophyte.... :(

    Best,

    Ben
     
  15. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    OK. So by all accounts you Receiver should be up and running because you have the FC connected to the SUMO (port 8) and yet it's not.
    That doesn't make sense. The Rx shouldn't even care whether there are Radians etc. You should be able to go and fly the C8 without the Radians and gimbal servos powered up.

    Aha! I wonder whether, when the Radian sensors are not powered up they're pulling down the PPM signal so that the FC, on the other half of the Y-cable doesn't see the PPM signal -- in other words the Radian sensor is grounding the PPM signal.

    I'm kinda surprised by that behaviour. Let me see if I can get an answer on that for you.

    Errr...don't count on that, Ben! :)
    I've not seen anyone on the forum trying to use a Y-cable -- at least, if they are, they're keeping it to themselves. :)

    You know, I don't really really know the answer to that. It's a very good question (and mine is not a very good answer).

    No need to apologize for being a neophyte. We all were once. In my case, with this question, I still am! :)

    Andy.
     
  16. Ben Freedman

    Ben Freedman Member

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    Yes... It seems like the un-powered Radians are causing the PPM signal from the RX to not make it to the MK Board... As soon as there is power, it's all good... Maybe a resistance issue, similar to how you need to add a resistor to the POT connection on the Radian servos...

    If you can get a better answers, it would be greatly appreciated!

    Best,

    Ben
     
  17. Gary Haynes

    Gary Haynes Administrator
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    Ben I think 2 recv should be fine. I am working on mine tonight. Just mounted the gimbal and have put a GR-16 on it. Just need to make sure everything is programmed. I'll give you an update soon.
     
  18. Ben Freedman

    Ben Freedman Member

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    Ya, after all this...what's another $80 for a GR-12? :)

    Tomorrow is my 2nd flight with this bird, and 1st with the gimbal attached. I'll use the y-cable setup for a day or two until the 2nd receiver arrives.

    Coming from a Draganflyer X6, I have to say, it's quite a step up! :)

    Best,

    Ben
     
  19. Gary Haynes

    Gary Haynes Administrator
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    Ben

    Here's the setup the way that I have it on my system. I have two receivers. The primary receiver is a GR-16 with a telemetry lead and is bound on position 1 on my MC-32 (For the MX-20, page 69 in the Graupner manual, describes how to bind the two receivers. You will also need to tell the MX-20 which one has the telemetry. This is done on the Telemetry screen, page 208 in the manual. You would make sure it is set to your first receiver that is running telemetry). I then bind the second GR-16 to bind position 2.

    Here's my wiring diagram. I am running a single 3S to power both the Radian/GR-16 and my FPV system.

    Slide1.png

    The wiring on the gimbal looks like this for the power/output from the GR-16 with a couple bits of velcro holding on the GR-16 (will add a tie wrap before I fly and reposition some wires).

    IMG_0818.JPG

    Depending on your channel setup the next steps will vary. I have Tilt on channel 7 and the MODE on channel 11. Check all of your wiring, power up the system, turn on your transmitter and hook up the Radian USB device to the Roll Servo. No need to power up the top deck and motors since they aren't being controlled by the gimbal section. Go into the Radian Software for the roll servo and set the MODE to 11. Write the change.

    Using the Mode switch on your transmitter check to see that it operates.

    Next up is the Tile Radian. Same process except on this one set the MODE to 11 and the Skew channel to 7. Write the changes and test the results with your tilt channel control.

    Since I had the props off I then tested the entire setup, powering up the whole copter and exercising all of the controls. Seems to check out fine. Next step is a flight check.
     
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  20. John Cunningham

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    Hey guys,

    Just to add a bit of technical info here:

    All the Radian IO ports are protected with current limitting resistors. If the Rx has a similar thing on it's output and the Radian is pulling down when there is no power, it might be the case that the peak voltage is falling too low for the FC to detect a logic one. This is especially possible if the signal is just fed into an input pin as some microcontrollers have quite a high threshold for a logic 1 to be detected.

    I don;t have the capability to try it myself - but it would be useful if someone could scope the signal and see how high the voltage is getting.
     

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