OttawaMaker

[OttawaMaker]

I resized my image and added it to this post.

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[OttawaMaker]

Thank you for the quick reply. I attached a photo of my robot. It shows the two 12V batteries feeding the Sabetooth controller. From there, 24V is fed to the regulator and the regulator output is fed to Arduino. I added a voltmeter to show the battery voltage. The lines from the motors are shielded and trimmed as close as possible to the controller. As per recommendations in a previous post, I removed the 12 capacitors on the motors.

I agree that it could easily be a noise issue. It could also be a connection issue. The output from Arduino to the controller is a simple pin stuck in the header and this isn’t the best way to make a connection. I will look into soldering it to the pad beside the header instead.

I will also try powering the Arduino from a separate battery, either a small 12V SLA or possibly a 9V battery. I don’t know what the current draw is yet, but for my requirements, I only need to run the robot for short periods of time in my test lab.Of course, I will connect the ground from that battery to the ground on the Sabertooth. In this case, I can eliminate the regulator circuit.

[OttawaMaker]

I spent the evening working on the robot. Here is what I did. I attached a couple of pictures.

– I removed all 12 capacitors from the 4 motors
– I cleaned up the wiring to each motor so that it is shielded up to the connections
– I removed the ground line from 0V on the 4 pin header, leaving only the line from Digital 3 to S1 (0V is internally connected to B-)
– 24V comes from the batteries to Sabertooth and then to the regulator

Input to the regulator is 24V, output is trimmed to 9V, which is fine for the Arduino UNO. I disconnected the 4 motors from the Sabertooth board and tried to measure changes to the open outputs, but readings were very unreliable. I imagine leaving them with no load was the problem. I reconnected the motors and measured the voltages across each motor pair as I moved the joystick to full forward and reverse positions. What I found is that the voltage swings were not symmetrical at all. They went from approximately +65V to -8V, a far cry from +/-24V.

The good news is that the noise problem seems to be gone now. After several minutes of testing, the robot only had a couple of instances where moving the joystick did nothing. Overall, it worked very well. I didn’t notice the error light coming on at all.

I also plan to alter the joystick functions. The default performance is froward/reverse in one axis and right/left in the other. Pressing the joystick button gives left/right in one axis, nothing in the other axis and twist gives forward/reverse. What would work better is to have forward/reverse in one axis and twist to do left/right. That way, I can move the robot in a straight line easily and apply a gentle twist to nudge it left or right. This seems to be a more natural way to operate.

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[OttawaMaker]

Here are the rest of the images for assembling an Anderson connector. Picture 5 is the key. You must orientate the parts as I have shown. Insert the metal part into the connector until you hear a click sound. If it doesn’t work at first, try again. The parts must be aligned correctly. Try not to get too much solder on the outside of the metal part. If you need to, use a small needle nose pliers to help insert the pin.

Sorry, when I edited this post, I thought I had to add the pictures again because they don’t show up during the edit. now I can’t get rid of them.

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[OttawaMaker]

I had never used Anderson connectors, so I was a bit confused as to how they work. With a little research, I figured them out and I thought it would be beneficial to others if I made a quick series of pictures. I numbered the pictures in order to make the process easier to follow. Since I can only add 4 files per post, I’ll continue in a new post.

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[OttawaMaker]

Yes, the Anderson connectors are meant to give us a way to disconnect the batteries from the circuit and then to the battery charger and vice versa. The trick will be figuring out exactly how to assemble them. I’ve never used these connectors before. There is a lot of help online for this.

My package included the TE-090-ADJ (Adjustable Switching Regulator Board Kit) and TE-900-004 (Programmable xBee Control Interface Package). The XBee circuit is on an Arduino shield, so all I have to do is provide power to the Arduino. I normally use 9V power supplies for them. Since documentation is a little sparse, here is how I see hooking it up. I tap off 12V from one of the batteries to power the regulator and the output of the regulator powers the Arduino. I adjusted the regulator output to 9V. I read the datasheet for the module on the regulator circuit and it says that input voltage can be as high as 30V. This is leading me to think that I can feed the whole 24V from my two batteries to it and not bother with using only one of the 12V batteries to power it.

[OttawaMaker]

Hi Paul,

I have the same scooter charger with the XLR connector. I searched eBay for XLR Connector and found lots of mating connectors. I’m not sure why these are three pin connectors. I haven’t measured the output yet to see what pins to use. I suspect that one pin is connected to the shielding. Overall, we need to figure out the best way to wire the batteries in place to allow connecting them to either the robot or the charger. In my case, I bought the Xbee controller, so I have to tap off from one of the 12V batteries to power the Arduino/Xbee circuit.

[OttawaMaker]

My application is for the robot to move in a straight line for 20 feet or so, stop and then back up the same distance. I do not need it to turn and if I replace two of the wheels with castors, I’m not sure if it will back up because the castors will first have to rotate to go the other way.

[OttawaMaker]

One more question. Can I turn TP-132-042 from a 4WD to 2WD system? I want one set of wheels to be on bearing mounts on a regular axle with no motors. For the powered axle, I will use the 78 RPM motors with encoders.

[OttawaMaker]

I checked your GIT site and I believe I found the code under XBee-ATR. I examined the code for the remote and I believe that I can throttle the max speed by changing the following lines of code.

// The switch is towards the joystick (full speed)
tempFB = map(FB, 0, 1024, -126, 126);
tempLR = map(LR, 0, 1024, -126, 126);

I believe that all I have to do is change the 126’s to lower numbers to limit my upper speed. That and perhaps not add 127 to them. I will have to experiment a bit. I don’t need much more than 60 ft/min.

I shouldn’t have any issues editing the Arduino code. I’ve written several Arduino programs to date.

[OttawaMaker]

The Arduino/Xbee page mentions that you also provide the custom source code. By this do you mean the program source code running on the two Arduinos? I can envision having to add external switches or IR/laser beams to act as limit switches so that the robot knows when I want it to stop. Will I have the ability to change the source code to add limit switches? If so, how many analog and digital I/O’s are still available?

[OttawaMaker]

OK thanks. Ideally if you could provide me with a quote for the parts I need with the options listed, I can get it ordered. I have to have a purchaser in another city do the ordering for me. If that is not easy to do, then I’ll have to provide this person with detialed instructions on what exactly to buy, down to each option.

[OttawaMaker]

In my solution, I am worried about having the Arduino output go to two inputs on the Sabertooth. Your Xbee solution looks good, but it is very expensive, so I need to know if it will do what I need. Please comment. Here is my application. I want the robot to carry a load up to 50 lbs and move in a straight line at speeds from 0.1 – 0.3 m/s. That’s it.

So far, I have selected the following assembly. This is the dump from your order page.

Welded Aluminum Robot Chassis – IG42 SB
Download Wheeled ATR Assembly Manual
Electric Power Hookup Kit
ATR and Vectoring Robot Hardware Kit
Electric Motor Hookup Kit
15 Amp Connector Set
Female Spade Terminal with Heat Shrink (Pack of 4)
ATR Wheel Shaft Set Pair 8mm Bore – 6 inch pneumatic
IG42 24VDC 078 RPM Gear Motor
Interstate 12 Volt 7.2 Ah Sealed Lead Acid Battery (SLA) – 0.250 Faston
Battery Bracket \ Customized Battery Bracket(s)
Charging System \ Battery Charging system
Sabertooth Dual 25A Motor Driver
RC Controller \ No RC Controller
Assembly \ Unassembled

If I add the XBee package, will it all interface perfectly and allow me to build exactly what I need? Notice that I changed the motors to 78 RPM because they should still give me more than enough speed for my application while increasing the load capacity to hopefully 50 lb.

[OttawaMaker]

I am building a robot for work and my boss wants to play with the remote control. :)

As for controlling the robot the way I need to, I want to move it along at a speed of between 0.1 – 0.3 meters/second. I thought that I would add an on-board Arduino UNO and use a pot to dial the speed I want with a LCD display to show the speed. I will calibrate the PWM signal to create the speed I need using the analogWrite() function. The PWM signal will feed into the sabertooth input. Can you verify if this will work?

I then thought of another idea. I may use a pair of Bluetooth enabled Arduino’s to create my own remote control. I would build the remote using an Arduino, LCD display, potentiometer and Bluetooth circuit. I dial the speed I want, press a button and it sends a command to the Arduino on the robot. That Arduino receives the command, interprets it and moves the robot. I will add a few beams along the path to tell the robot to stop or slow down when it interrupts them.

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