Picking The Right Sabertooth

Question

Hey guys Im looking at getting a Sabertooth on order and not really which one to go with. I'm using a Jazzy Elite Electric Chair, that states a 40 amp system, but cant find anything on the motors for amperage. Doesn anyone have some experience with the Jazzy that can give me some insight?

Dana W · Answer

Im guessing, a 2x 32 Sabertooth (40amp system, 20 amps per motor)would work, but concerned that the peak could go over the 64amp peak of the Sabertooth, so wondering if i should go to the 2x60, or is that complete overkill?

thetechguru · Answer

Sorry I can't find the post right now. A couple of years ago someone did a oist about sizing controllers. I think they said to go 10% over the motor rating, so 2x32 should do it. Maybe get away with a 2x25. Alan

Dana W · Answer

Thanks for the response I searched again this morning for any kind of rating for the motors, and nothing. But nearly all applications like this are using the 2x25, and since i'm going to be crawling with it, and no sudden high torque starts, i'm thinking the 25 will be ok. If not Ill order the 32 and keep this one as a spare to play with on another project. If i don't smoke it of course lol :O

Dunning-Kruger · Answer

@Dana 2 x 25 is the one you want You could probably get away with the 2 x 12 if your bot is light... All sabertooths have a built in over current protection which will shut down the sabertooth if you motors try and pull too much current... Remember max of both motors and possibly the controller is listed at 40amps... My guess that is extreme where both motors are close to maximum output... I doubt with what you want to use it for that each motor would not draw more than 10amps... the 2 x 25 will be more than adequate for your needs... What are the motor's rated voltage?... If the are 24V, running the motors with 24V instead of 12V will drop the amps needed...

Dana W · Answer

@Richard R Thanks Richard IT's a 24 system, but i it's 12v going to each motor. But ive read that it could be 24 going to each, but 12v for the motor and 12V for the brake, so not completely sure. The postings are so random in opinion its hard to figure it out, and nothing listed in the paperwork or on the chair. I think the base is about 60lbs.

Dunning-Kruger · Answer

The motors are meant to carry people, right? So if your bot when finished won't be weighing hundreds of pounds and you won't be using it in extreme conditions (like robot fighting LOL) then the 2 x 25 will do you just fine... Remember 2 x 25 means 25amp rating on each of the 2 channels so each motor has available to it a continuous 25amp draw... You'll lucky (if the above conditions apply) if each motor draws more than 10amps each on average... A good formula to remember... Watts/Volts=amps Using the above formula you can see by increasing the volts means you will use less amps... That's why I asked whether you were using 12V or 24V to drive the motors...

Dana W · Answer

@ Richard R Yes, absolutely right, no people, and only adding about another 20-30 lbs tops, so it wont be working as hard as intended by design, plus when moving it will be at a very slow speed for short distances. Still learning on the electrical side of things, obviously lol. Im used to designing Industrial machines, then pass it along to the Electrical guru's to make it actually move, so this is one heck of a learning curve for me.

Dunning-Kruger · Answer

@Dana no worries ... Like I said, the sabertooth's have a built in overdraw protection so you worst case scenario you bot shuts down trying to climb a steep hill while overloaded with weight... One thing about the sabertooth I would caution you on... there is no reverse polarity protection, so if you accidently reverse + and - .... you will get to experience the wondrous and mysterious magical blue smoke.... .... Don't ask me how I know....

Dana W · Answer

@Richard R LOL Yes i saw that in one of the videos, dont need a room full of magical smoke, Sad Day Thanks again, i'm much more at ease now! Now for the Mini ITX. Need bags full of money

kamaroman68 · Answer

DanaW going bigger won't hurt anything. I use roboclaw which is sort of like sabretooth. I burned one channel of a 2 x30 out and had to send the controller on for repair. I am using wheel chair motors that were supposedly rated at 20 amps. My bot weighs in at just under 180 lbs though. Tech report showed an over current condition happened. This controller also had built in over current protection but still burned a component on the board. I upgraded to robocclaw 2 x 60 and have never looked back. I use the 2 x 30 roboclaw for the shoulders wheelchair motors now, but these motors are not nearly as strong as I had hoped. Anyways good luck!

Dunning-Kruger · Answer

You think that's bad... Our Canadian dollar has dropped so much, I need a wheel barrow full of money just to shop in the ez robot store... stress

Dunning-Kruger · Answer

@kamaroman68 ...Yours could have had a fault... And it's a Roboclaw (although based on the Sabertooth design) a completely different company and a different design... Every sabertooth I happened to over current have just shut down and reset... None burned out....

Dana W · Answer

@kamaroman68 I was planning on the 2x60, but trying to split a dollar for ways this week, lol , so decided to got 2x25, and baby it for now. I wa on the fence for the Roboclaw, or the Sabertooth, and i hadn't seen any negative feedback at all on the ST so just went with the crowd. @Richard R We just need to talk DJ in to running a buy one, get one free sale one day a week, for the Canadian shoppers!

Dunning-Kruger · Answer

Ironically (actually I do know why) it's a Canadian business that list products in US dollars....

Dana W · Answer

True

Dana W · Answer

Received my Sabertooth, and trying to avoid smoke I'm set up with Pin 1 Up, 2-5 Down, and Pin 6 Up as shown in the Sabertooth Tutorial, and set up. I plugged into D0, and wired up as shown, but not getting any kind of voltage to the M- M+ on either motor output. Any thoughts?

Dunning-Kruger · Answer

1, 3 and 6 up (rest down) if your are using a non lipo or li-Ion and if your using 38,400 baud... This is for a 2 x 12 sabertooth... I am assuming it is the same for the 2 x 25... You have the battery connected to the sabertooth, right? sendserial(D0,38400,127) #full forward channel 1 sendserial(D0,38400,255) #full forward channel 2 sendserial(D0,38400,0) #stop both channels

Dana W · Answer

Using an NI-MH Battery pack. How do i double check/set the Baud? Reading the manual now, but haven't made it that far yet

Dunning-Kruger · Answer

Ok, make sure everything is hooked up correctly then in a script enter the below... then run it... #enter in a script S1 on the sabertooth to D0 data pin (white pin) 0V or ground on the sabertooth to ground on D0 sendserial(D0,38400,0) #stop both channels sleep(1000) sendserial(D0,38400,127) #full forward channel 1 sendserial(D0,38400,255) #full forward channel 2 sleep(4000) sendserial(D0,38400,0) #stop both channels

Dana W · Answer

Using the ST Movement panel, plus script? I can see the Baud rte in the movement panel, plus the settings you have listed here. Power is connected from the EZB and Signal wire to S 1

Dunning-Kruger · Answer

No try the script I gave you separately .... Are there any leds lit up on the sabertooth? To be clear no power from the ezb, just 2 wires S1 and grn... battery is separate to the sabertooth

Dunning-Kruger · Answer

S1 to DO white data pin, grn or 0V (on the sabertooth ) to D0 ground (black pin).... no other wires to the sabertooth

Dunning-Kruger · Answer

Sorry about the bad picture had to throw it together so to speak...

Dana W · Answer

yes, I had 1 Blue LED on. "The EZ-B connects to the GND, +5 and Signal to the Sabertooth. The Signal from the EZ-B connects to S1 on the Sabertooth." This is how i hooked it up, and was understanding this to mean to hoo k the + and _ plus Signal to S1

Dunning-Kruger · Answer

NOOOOO... LOL Just 2 wires (see my picture)... Ground on sabertooth (or as mine says 0V) to grd (black pin) on D0.... S1 on sabrertooth to white data pin on EZB... DO NOT connect anything to +5 on the sabertooth or the red pin on the ezb

Dunning-Kruger · Answer

See my pic

Dana W · Answer

Got it I copied that from the ST Tutorial :O Hope its still ok, no smoke, but, fingers crossed. So common ground from the opposite side as the Motor terminals. All i have for control is a start button, no movement panel, which do i use?

Dana W · Answer

The grounding makes more sense now Didnt make sense to get its power from the EZB.

Dunning-Kruger · Answer

The +5V on the sabertooth is a bec... it is used to power a device like a radio receiver for remote control...

Dana W · Answer

So much to learn! Pushing through the fear of blowing things up lol

Dunning-Kruger · Answer

Just don't reverse the polarity on your shiny new sabertooth... You gotta' love the smell of burnt electronics in the morning, don't ya'

Dana W · Answer

Only part im still confused on, is that the script only gives me a Start button, with no other controls. My apologies, but i missed something along the way.

Dana W · Answer

lol ya, going to save that kind of sillyness untill day 2 :O DAM! Hoping to get this part figured out before the weekend. Electrical panel and came today with the ST, and the Motherboard and power supply come tomorrow. Getting excited.

Dunning-Kruger · Answer

Yep, just press start button and the script will run for about 5 seconds then the motors and script will stop... well it should, anyway... It is just a simple test to see if the sabertooth responds... running and then stopping both channels (motors)

Dana W · Answer

Ah ok ic Thanks so much for taking the time, Richard. Very much appreciated!

Dunning-Kruger · Answer

Ah, no worries... We'll get you up and running before you blow ....your saber... I mean complete your project....

Dana W · Answer

Ill need it, thats for sure! lol

Dunning-Kruger · Answer

@Dana... Just a though... Do you own a multimeter? Maybe a good idea to connect it to your wheelchair motors to see generally what kind of amps they are pulling... This will help you determine if both motors are running ok...etc... I usually do this (for motors and electronics) for my projects for no other reason than to be able to estimate how long my batteries might last...

Dana W · Answer

Yes i do, and definitely need to, use it alot as i move through this project. I have someone who will be taking care of the heavy lifting parts of the project, but im pushing through a lot of it so i have a good understanding of how things work on the electrical end of things, but don't trust myself enough, for the whole project.

Dana W

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