I'm new to robotics/electronics. I'd like to make a RC robot

[JDPD96]

Hi
I'm 15 and new to robotics/electronics and i want to build a RC robot
i want it to be 4 wheel drive and before i go out spending all of my money on parts i was hoping that someone here could help me with this little project.
I've been looking around on forums for a few weeks now and i can't find anything to help me with this.
What i want to do is make it with 4 motors, but i cant afford to buy 4 ESCs to use the motors i was hoping that there is a way to only use 2 ESCs
I heard that you can have 2 motors to 1 ESC and when you push forward on the transmitter both the motors go forward but i'm not sure how to do that.
If this helps, the things that i have are a 6 channel transmitter and receiver, a 6V battery cradle with 4x 1.5V AA batteries in it and if i end up understanding all of the electronics for this robot i'm going to buy 4x 6V DC motors and 2 ESCs (if i can use only 2 ESCs) and if i have to, battery packs for the ESCs ( i think they use their own battery).
Another thing i was wondering about is that the ESCs that i've been looking at have a continous current and a burst current, the one i've got my eye on has 30A continuous current and a 40A burst current i struggle to understand what that means, i think it is the amount of amps that go through it that the motor draws or needs to work but im not too sure
Thanks for reading and i hope someone can help

[Neogs Red]

well, to drive my first robot project i used an e-flight micro controller out of a remote control helicopter. it worked fine for 6 volts and used the servos from the $50 robot tutorial quite well. only thing is that after a while the micro controller started to heat up and i needed to unplug it to let it cool. other then the draw back it worked quite well.

[Soeren]

Hi,

quote author=JDPD96 link=topic=14380.msg105593#msg105593 date=1314765775]
[...] i want to build a RC robot
i want it to be 4 wheel drive
[/quote]
Usng 4 motors for that is not the best way. Take a look at how (quality) R/C cars do it, after all, it's an R/C car that you want to build, so spy how the large companies made them - i.e. with diferentials. Some use only one motor and have 3 differentials, one on the front axle, one on the rear axle and one on the driveshaft connecting the two.
It would be very hard controlling 4 sticks.


quote author=JDPD96 link=topic=14380.msg105593#msg105593 date=1314765775]
Another thing i was wondering about is that the ESCs that i've been looking at have a continous current and a burst current, the one i've got my eye on has 30A continuous current and a 40A burst current i struggle to understand what that means, i think it is the amount of amps that go through it that the motor draws or needs to work but im not too sure
[/quote]
A DC motor will draw a larger burst of current when starting and an even larger burst when reversing direction, compared to normal running.

Before you buy any ESC at all, please post the datasheet on your motors, or at least a link to them.

[The Headacher]

If the motors are small enough, wouldn't it be possible to use 2 motors in parallel on the esc's and use differential drive? I don't know if that is what he wants, but if he's going to continue in robotics differential drive is going to be much easier to use (turning on the spot like a tank). Also saves the trouble of making a steering mechanism.

Just a thought! 

[Soeren]

Hi,

If the motors are small enough, wouldn't it be possible to use 2 motors in parallel on the esc's and use differential drive?

There's a reason why I wrote that it's not the best idea to use two motors for the same side - they won't spin the same speed, even with the exact same voltage.

Also saves the trouble of making a steering mechanism.

Anybody that think of parts of the robot construction as "trouble" should probably choose another hobby - Stamp collecting anyone   

[The Headacher]

they won't spin the same speed, even with the exact same voltage.

But if the wheels are on the ground, they will have the same speed as long as there is no slip. If one has more resistance, it will draw more current, right (please forgive me if I'm wrong, my electronics is quite rusty)?

Anyhow, just thinking out loud here.. I come here to learn too  .  

Anybody that think of parts of the robot construction as "trouble" should probably choose another hobby

I'm just saying that creating your own steering mechanism is more difficult than mounting 4 motors at each corner. For a first time builder, that might be important. Me, I chose an R/C car as a base for my robot, I was not that keen on building everything from scratch yet, because I don't have the space to create a workshop to machine all the parts I would need creating my own base. I have the knowledge and the expertise, but not the equipment. Also, I might be a bit lazy .

[JDPD96]

Ok, so now i understand that it is possible to have several motors to 1 ESC.
But i am really new to this hobby and i dont know the difference between having things in parallel or series.
If someone could give me an understandable definition of parellel and series that would be great.
sorry if i sound stupid by the way

[Sylvestre]

How are you going to transmit your data?  I'd take a look at these motor drivers http://www.dimensionengineering.com/index.html

Just a thought, but you could just use one motor and then a servo for the steering mechanism.

With differential drive, you dont really get to have the fun of drifting and what not 

[JDPD96]

what i was hoping to do is use it as a little helper type rc robot
first i was going to make it a 4 wheel drive basic robot/car
then when i've done that use a servo or 2 and make a gripper or a scoop or something
the 2 ESCs should only take 2 of my 6 channels so i've got 4 channels to play with 
i have 2 servos that are 360 degree continuous rotation i just found those in one of my draws so i hope to put them to use as a little add on for my bot

[waltr]

Ok, so now i understand that it is possible to have several motors to 1 ESC.
But i am really new to this hobby and i dont know the difference between having things in parallel or series.
If someone could give me an understandable definition of parellel and series that would be great.
sorry if i sound stupid by the way

Have you read all of the tutorials and articles found under this page's title? If not they are a good start to learn.
Next, you just need to start playing with this stuff. You'll make lots of mistakes (we all have) but its part of learning.

For addition ideas, and what might work or not read through the many, many threads on this forum. There have been many others that just started out and have asked questions here and got good answers (your questions have been asked here before).

Then there is Google, Wikipedia and other information sources on the web. Typing in "parallel" and "series" will get you the definitions.
http://en.wikipedia.org/wiki/Parallel
 

[JDPD96]

I'm going to have a long look through the forums now
thanks

[Sylvestre]

Ok if your looking for a gripper look at the admin's robot gripper

Custom Robot Arm and Gripper Demo

It's really easy to make.   

[JDPD96]

That is a really cool robot arm
i might even be able to use my school's laser cutter to make the pieces for my own robot arm
i've decided that i'm going to use my servos that i have now to push 2 micro switches to drive the motors, i'll have 4 wheel drive, i'll put 2 motors in parallel to 1 micro switch and when that is all done i can start making the gripper.
If i've done anything wrong here please correct me
Thanks everyone

[Soeren]

Hi,

But if the wheels are on the ground, they will have the same speed as long as there is no slip. If one has more resistance, it will draw more current, right (please forgive me if I'm wrong, my electronics is quite rusty)?

If there's no slip, yes, then one motor will be loaded harder than the other. This leads to faster wear down, so it have to work even harder and the difference will be amplified and you're in a steadily increasing black spiral.
The sensible solution is to just use one motor and if needed choose one with double the brawn if needed, it will take up less space than the two others and it will give less engineering trouble.

Anyhow, just thinking out loud here.. I come here to learn too  .  

Learn or question established knowledge?   

I'm just saying that creating your own steering mechanism is more difficult than mounting 4 motors at each corner. For a first time builder, that might be important. Me, I chose an R/C car as a base for my robot, I was not that keen on building everything from scratch yet, because I don't have the space to create a workshop to machine all the parts I would need creating my own base. I have the knowledge and the expertise, but not the equipment. Also, I might be a bit lazy .

Also, you need to realize that "trouble" is a negative word, while "challenge" is positive...
"The steering is nothing but trouble" and "The steering is a real challenge" actually means the same, but the former is said by "glass half empty" guy and robot building is really for those with a "glass half full", if you catch my drift.

[JDPD96]

This will probably sound like a stupid question to you all but why will one motor be loaded higher than the other motors?

[Soeren]

Hi,

This will probably sound like a stupid question to you all but why will one motor be loaded higher than the other motors?

DC motors of the same make and model will not spin at exactly the same speed and if forced to, one will be harder loaded, as it is trying to speed up compared to the other to the other (in a 2 motor setup like you described).

Have you decided on which motors to use?
As mentioned, going for one larger motor will give you the torque without the tears and you'd just use an idler wheel at the other end of the track, so it's a cheaper and easier solution in several ways.

[The Headacher]

If there's no slip, yes, then one motor will be loaded harder than the other. This leads to faster wear down, so it have to work even harder and the difference will be amplified and you're in a steadily increasing black spiral.

Ah, yes that makes perfect sense, thanks!

Learn or question established knowledge?   

Learn .

Also, you need to realize that "trouble" is a negative word, while "challenge" is positive...
"The steering is nothing but trouble" and "The steering is a real challenge" actually means the same, but the former is said by "glass half empty" guy and robot building is really for those with a "glass half full", if you catch my drift.

I tend to think in problems and solutions, rather than challenges. For me, that's not negative. Every problem is an opportunity to learn. I must admit communication is not my greatest skill though, you're not the first to think I'm a negative (or not so positive ) person.