Hi,
I’m interested in using the 4WD-1 rover, but I would like to be able to control the wheels by the kind of 3 pin set up you find on the Lynx 6 arm controller. From what I can tell, the 4WD-1 comes with DC motors. Is it possible to swap these out for servos that can do continuous rotation and be driven by the Lynx 6 arm controller? Or even, can the existing motors be driven by this controller?
Thanks,
Nick
Hi, Nick.
I would think that if you were to modify the 4WD-1 chassis to use servos for the drivetrain instead of the gearheads it comes with, you’d be introducing a whole lot of mechanical issues, which could quite easily add up to eliminate virtually every positive aspect of using this chassis to begin with.
If you want to drive the base’s motors like continuous-rotation servos, I would think that you’d be a lot better off using the stock motors as supplied, and driving them with a Sabertooth 2x10 R/C motor controller, as shown here. You’d have the robustness, power, and speed of the stock chassis and motors, and the Sabertooth accepts pulse-train control signals, just like a pair of servos would.
Seamus,
Thank you for your response. I am not actually in possession of the rover or the motor setup, so I am trying to figure out how compatable it is with what I want to do before getting the rover.
If I understand you correctly, the motors that come with the rover can be hooked up to the Sabertooth, which in turn can be hooked up to the controller on the Lynx 6 arm. (I do see three sets of wires coming off of the Sabertooth that look like they should work with the Lynx 6 controller.) If this is the case, would I need 4 Sabertooth units, one per motor? I should mention that my goal is to drive the rover autonomously. Though now that I think about it, perhaps that means that if I want continuous drive, the positional commands that get sent to the Lynx 6 wouldn’t be optimal. I suppose an alternative would be if there is a wheeled platform that is conducive to being driven by something like the Lynx 6 controller and could support that arm.
-Nick
To use the Sabertooth 2x10 R/C with the 4WD-1 chassis, you only need one Sabertooth controller, as one controller can drive two channels independently of each other (right and left). Further, you can “gang” motors on each channel, provided that your motors’ current consumption is within the capability of the controller (10 amps per channel continuous, 15 amps peak). The 4WD-1 shouldn’t have any problems being driven by the two channels of a single Sabertooth.
The Sabertooth uses servo-type commands so, for example, you would have its left channel connected to, say, servo number 30 on the SSC-32 servo controller (controller for the Lynx-6’s servos), and the right channel to servo number 31. With both 30 and 31 set to their midpoints at a pulse length of 1.5 mS, you get no motion from either side’s motors. If you leave 31 at the center position, but set channel 30 to, say, 1.0 mS, then the right side motors stay still, and the left side runs at full speed forwards, spinning the robot around to the right indefinitely until you tell it to stop by setting channel 30 back to the neutral point at 1.5 mS.
Rather than servo positions with a discrete position for each pulse-length, it may help to think of them as two independent throttle controls, allowing for smooth acceleration both forwards and backwards for each pair of motors on the right and left sides of the robot.
If your looking to go autonomous with your rover, I believe an ABB and an micro such as the Atom/Atom pro would be a good option. This will allow you to plug and play different sensors onto the robot and you can program the micro to store all the commands such as “if the sensor sees something in front of it, it will steer away from that object”.
Looking at the assembly instructions for the 4WD1, it is unclear that I would need the Sabertooth. It looks as though the motors have two pin leads coming off them that I can plug into the SSC-32 controller. But since I’m not entirely sure, my question is this: if I got the 4WD1 kit sans electronics, could I run everything off of the SSC-32 controller along with the L6 arm? Or is it necessary to have the 4WD1 motors go through the Sabertooth and then have the Sabertooth go into the SSC-32?
In short, my goal is to run both the L6 arm (which I have and obviously comes with the SSC-32) and the 4WD1 off of the SSC-32. What is the bare minimum that I would need to get in order to do this?
Thanks again.
no, its absolutely necessary for the motors to go to the Sabetooth controller. But im not sure you can connect it to the ssc-32??? I think you will also need an ABB and Atom as well.
here is a tutorial of what I mean.
lynxmotion.com/images/html/build065.htm
the tutorial shows the scorpion being connected to the mini ABB and atom. IF you want you can do this with the sabertooth and also have the SSC-32 connected to the ABB. Same thing.
The Sabertooth 2x10 R/C controller wants to receive servo-type PWM commands, and will therefore work with anything that will produce said PWM pulse streams. If you plan to pair it with a Lynx-5 or Lynx-6 arm, you’ll already be using a SSC-32 or similar servo controller, and will have extra channels available to drive the Sabertooth.
The servo controller will need to have some form of processor or intelligence controlling it, be it an onboard microcontroller (Atom/BotBoard, stamp, PIC, AVR, etc.), or an offboard computer (cable, bluetooth, Wi-fi, etc.). For just the motion-control portion of the equation, you’d be controlling the motors of the 4WD base with the Sabertooth, which would receive its control signals from the SSC-32, which would also control the axes of the arm. The SSC-32 would receive its commands from “something else”, via its serial input line.
http://www.rthtg.net/i/block_diagram_01.gif
Alternately, you could spend more money and get the Sabertooth 2x10 (non-R/C) version, which would be capable of accepting serial commands directly from your control logic, but since you’ll already be using an SSC-32 onboard to control the Lynx-6 arm, the 2x10 R/C is a bit less expensive, and utilizes the servo-type PWM pulse trains generated by the servo controller.
my bad. I was thinking of the ABB and atom as programmed commands. Thought he was using a ps2 controller. my mistake, however that totorial is still useful and may help you understand how to connect the sabertooth to the SSC-32.
Yeah, I guess that my previous post(s) have been assuming that since no mention was made of using a particular handheld controller or prebuilt program, that the intent was to come up with some custom programming and routines to provide the drive and arm-control commands.
If the intent is to use some sort of pre-packaged solution, then you’d want to modify your approach to divvying up the control to accommodate the outputs that your controller and/or program provides. Otherwise, if you will be writing your own code, then it’s a little more cost- and I/O-efficient to let the SSC-32 handle the generation of control pulses for the Sabertooth.
If there is anything like a downside to having so many options available to you, it’s that there are so many different ways to approach a potential solution to a problem that it can be hard to figure out which one is the best fit to a situation.
Guilty. Happens to me all the time! So many options to chose I have a hard time picking. 
Please forgive these questions, but I am much more familiar with the software side of things than with the hardware.
Okay, having procured the Sabertooth and 4WD-1, I have a couple of questions. When you say it’s possible to “gang” motors on each channel, does that mean for example that I would take the red (+) wires of the two left side motors and merge them to one wire and the two yellow (-)wires of the same side and combine them to a second wire and then connect those two merged wires to the Sabertooth? If so, where would the merged red wire go and where would the merged yellow wire go? For example, would it be red into M1A and yellow into M1B while the merged red and yellow from the right motors would go into M2A and M2B respectively? And as to the battery that would run the Sabertooth, I’m assuming it would have to be a separate 6-24 V battery from the battery used for the SSC-32? And finally, there are three sets of leads coming out of 0V, S1 and S2. I’m assuming S1 and S2 can go into any one of the servo channels on the SSC-32 and just be sent commands just as any other servo would be, but what about 0V? This is said to be a circuit ground, but where would it plug in to?
Thanks again.
0 v goes to the vss (ground) of the ssc-32 or what ever is controlling it the 5v can power a micro but not servos ,and be careful of battery polarity u can control both channels with 1 pin here read this
trossenrobotics.com/images/productdownloads/DimensionEngineering_Sabertooth2x10.pdf
this things sweet
So I have the 4WD1 motors wired to the Sabertooth and I have a battery wired in. The turn, fwd and flip pwm leads are plugged into the SSC-32 and I’m left with one issue: what commands to send the SSC-32 to drive the motors. I attempted the typical
#PS\r\n
but this did nothing. Are there particular instructions that the SSC-32 needs to pass to the Sabertooth?
Thanks.
the same commands u use to control servos ie. 1500 = neutral and 1000
will be full forward or backwards depending on how the motor leads are wired ( u can switch them to make both motors turn in the same direction ) and 2000 will be reverse first check that ur dip switches are correct for the type of control ur using , just treat them as servos basically ,
the same commands u use to control servos ie. 1500 = neutral and 1000
will be full forward or backwards depending on how the motor leads are wired ( u can switch them to make both motors turn in the same direction ) and 2000 will be reverse first check that ur dip switches are correct for the type of control ur using , just treat them as servos basically ,
This is what I thought would be the case. So I’m sending the correct commands, but apparently I don’t have the dip switches set correctly. I’m reading through the Sabertooth documentation, but I’m not sure what type of control I want. The Sabertooth is going to be receiving its input from the SSC-32 controller, should I be using Analog, Simplified Serial…?
Thanks.
PWM
I think you’re getting the sabertooth versions confused - are you running the 2x10 (with screw terminal inputs and side heatsinks) or the 2x10RC (with servo pigtail inputs and no side heatsinks)?
If you’re using the 2x10RC, you want independent, linear, no autocalibrate, no timeout mode.
