T rex jr hookup questions

i searched the motor controllers forum and didnt find t rex jr in any subject line so here goes: i am totally new to robotics, ive been into rc’s for quite a few years, but decided i would like to try robotics. i purchased a tamiya track kit and dual motor transmission, and t rex jr motor controller… i want to set up the electronics before i build anything else, but being the newbie i am, cant figure out where to hook everything up… im good on hooking the motor leads up, and im fairly certain the battery main power goes to the 2 contacts between the motor contacts, but i am unsure… btw- im running this all off of a hitec 3cfm radio, mixed function, and the bec jumper in place, soldered a female-female jumper together (for the bec), where does this hook up on the t rex jr? looking at the back of the controller,on the right side theres some abbreviations that i dont know what they mean such as: G, SO, and SI. i know what rx and tx means, but the others im totally unsure of…also, there is a jumper on the G, and SO terminals, what is this for? next question: im running a pistol grip controller, and in mixed function will allow me to independantly control each motor via the “steering wheel”, correct? do my channel jumpers go from the rx servo outputs to ch1-ch3? sorry for all of the newbie questions, but i dont wanna get stupid and fry this thing… thanks for your help!!

nate sanders

btw- do you guys have a switch that would be ideal to hook up to the ch4/flip leads? my tank will have full tracks.


Before I go into too much detail answering your questions, I’d like to first point you to the TReX Jr user’s guide. I think this will give you a lot of the information you’re looking for (e.g. what the various input/output pins do, how to hook things up to them, what the various jumpers do, and what the LEDs mean). Please look this over and then ask any questions that remain unanswered.

Yes, with the mix jumper in place on the TReX Jr, the steering wheel channel will affect both motors, as will the trigger. The trigger should make both motors turn in the same direction at a speed dependent on how much the trigger is depressed (so the bot will move forward or backward). The steering wheel should make both motors turn in opposite directions at a speed dependent on how much the wheel is turned (so the bot will spin either left or right). Without the mix jumper in place, the steering wheel would control the speed/direction of one motor and the trigger would control the speed/direction of the other.

I’m not sure what your “channel jumpers” are. Can you give me more information about these? Are they something that came with your radio? You should be able to safely leave unused RC channels completely disconnected.

Unfortunately we do not have any switches that would work as a flip-indicator, but you could always hook up your radio’s third channel to ch4/flip and use that to enabled/disable flipped mode.

- Ben