Looking for a little direction....wirelessly

[Robotics12]

So, group has decided to do something along with lines of a wireless cart. It will be electric, the pedals/steering wheel will be there but it is all wireless. We are in the stage of 'what we need' and was wondering if some could give some input on what they would recommend but so far I would assume we need a microcontroller(arduino), would I need two...one on board to receive and other to send?

[RITESH29]

If you want a wireless control over Robot there are lot of module like X Bee but ihave used only RX and TX at 433MHZ with HT 12E/D ....

[Robotics12]

Right, XBee was a possibility. Main question was just making sure all the 'pieces', as far as part and logic, are together before one dives into this project.

[Soeren]

Hi,

Main question was just making sure all the 'pieces', as far as part and logic, are together before one dives into this project.

Some things may just show up when you're actually implementing it, so dive in with what you have and refine along the way.

You don't need a servo for the gas pedal, a motor controller can be controlled directly from the Arduino.
If it never have to reverse the motor, a simple MOSFET (plus a little interface) will do, feeding it PWM from your Arduino.

[Robotics12]

Thanks for the feedback. Thing about 'diving in' is that we need a plan and outline of what needs to go on right now. Wish we could just jump right in. So, my idea was with an Arduino and use an Pololu JKR 21v3(any other recommendations?) for the motor controller and microcontroller.

[Soeren]

Hi,

Thing about 'diving in' is that we need a plan and outline of what needs to go on right now. Wish we could just jump right in.

A sketch on a napkin should suffice.

So, my idea was with an Arduino and use an Pololu JKR 21v3(any other recommendations?) for the motor controller and microcontroller. If the plan is for someone to sit in the cart and drive with everything wireless, I could just one arduino being on the cart communicating via bluetooth with a laptop...or will I need two microcontrollers or?

One should be enough.

So, you mentioned I would need just two servo's for steering and brake? With these two questions being answered, I seem to know the general idea of how to proceed. Thanks.

No, I said that you don't need a servo for the speeder.

Most of the braking can be done by the motor itself, but a mechanical brake will probably need a lot more than the average servo can handle, so you may need to build special servos for that.

Almost likewise with the steering, especially if you want a steering wheel to move along - you could add a sprocket wheel to the steering column and then use a sprocket wheel as can be had for a servo and a roller chain to connect them - will need to be a substantial servo though.

And I wouldn't like to be sitting in it while remotely driven - As a teen I got to see both my knee caps in all their white and bloody glory when being in a pedal go-kart pulled at around 65 km/h by a tuned moped, when the steering suddenly jammed with me going directly towards a parked car. I literally made braking stripes with my knees on the pavement when I bailed out - The only time where a crash helmet actually did me good.
So, safety first... One of you may have a dog to test with

[Daanii]

I can't figure out exactly what you plan to do.

Is the person sitting in the car going to drive it? If not, what are you going to use for the driver to control the car?

[Robotics12]

I was looking into bluetooth because it was mentioned to possibly using a smart phone in the future for possible steering. Would this suffice for my bluetooth shield?
http://www.trossenrobotics.com/p/bluetooth-shield.aspx?feed=Froogle
http://iteadstudio.com/store/index.php?main_page=product_info&cPath=18&products_id=179

My process was having a motor controller(pololu jkr) for the power supply/motor and the microprocessor(with bluetooth) to receive and send to the motor controller. Also the servo(s), Soeren mentioned the brake, so maybe have a 'super' servo for it.

[Robotics12]

Someone along the lines of this:

It's Not Easy Being Greased
Skip to 1:15 mark. This is similar although it want to remote controlled, rather someone sit in it with a steering wheel and drive. (With the steering wheel, gas, brake being wireless)

[Soeren]

Hi,

Thanks for both responses. To clarify more, the idea is the have a buggy(go-cart), electric, with someone sitting in it using a wireless steering wheel and either wireless pedals or a wheel with a brake/gas button/trigger on it. So, just think of your typical go-cart and that is what it will be except the wheel/gas/brake are wireless.

Very expensive way of replacing good copper

I was looking into bluetooth because it was mentioned to possibly using a smart phone in the future for possible steering. Would this suffice for my bluetooth shield?

Yes, as long as you just need slave units.

My process was having a motor controller(pololu jkr) for the power supply/motor and the microprocessor(with bluetooth) to receive and send to the motor controller. Also the servo(s), Soeren mentioned the brake, so maybe have a 'super' servo for it.

I once saw a brake servo for a semi-large model car (smaller than a go-kart) made from a wiper motor, and that should be a cheap find at a car junk yard/"used part reseller".

A disc brake from a bicycle or a moped/scooter (or homemade) should be easy to install and probably the simplest to get working reliably.

Do you have the motor or have you decided on a particular model?

[Robotics12]

No particular motor yet. Maybe two 24V 250W scooter motors.

And when you mention having 'slave units', what exactly are you referring too? Sorry for the confusion.

And yes, the wiper motor is a possibility. I saw that completed before and seemed like a possible idea.

Also, is there a recommended bluetooth shield between the two I posted above?

[Soeren]

Hi,

No particular motor yet. Maybe two 24V 250W scooter motors.

OK, that would be easy to control with a MOSFET, but why not  a single 500W unit?

And when you mention having 'slave units', what exactly are you referring too? Sorry for the confusion.

With Bluetooth you have a master/host and a slave. The modules you linked to cannot be hosts, so you need the other end to handle that (a laptop or similar could be used).

Also, is there a recommended bluetooth shield between the two I posted above?

I don't know either of them. Perhaps you can find some reviews of them.

[Daanii]

No particular motor yet. Maybe two 24V 250W scooter motors.

Those motors would be too beefy for a Pololu jrk 21x3 controller. That controller can handle the 24 Volts, but it can only take 3 Amps continuous, 5 Amps peak.

But I do like those controllers. I am using a Pololu jrk 12x12 controller to drive a windshield wiper motor to turn the steering in a car. It works well. It has a nice PID control algorithm right on the chip, so you just send it position feedback, and you can use the windshield wiper motor like a big servo.

As to the rest of your project, it all sounds interesting.

The wireless part of it I can offer no help on. To me, it seems like you would want to use a wired steering wheel and pedals to start, if you are going to have the driver sitting in the go-cart. Then add wireless later if you want to let the driver do the driving remotely.

That's because I think you will have your hands full doing the drive-by-wire throttle, steering and brake actuators. As Soeren said, you don't need any actuator for the throttle--just send your throttle signal to your motor controller. But for the steering and brakes, you need actuators that turn an electrical signal into mechanical motion.

For steering, as I say, we hooked a windshield wiper motor up to the steering column. We took off the steering wheel completely, and attached the motor just above the steering gearbox. It works pretty well for us. But I don't know too much about a go-cart's steering linkages. It may not work well for you.

For brakes, I'm not sure a servo motor will have the torque to pull on the brake cable with enough force. But a motor for a car power window or a power seat should have enough torque.

For both steering and brakes, you will need to control the motors. That will be the hardest part of the project, I think.

Good luck with this.

[Robotics12]

Instead of two 24V, think we might end up using 36V 500W motor.

[Admin]

Microcontrollers are for autonomous robots. But you want RC. Why not just use a remote control and a speed controller? 

[Robotics12]

Don't we want to go RC.

[Daanii]

With the brakes, if we go with wiper motor, would it be a possible idea to just have one arduino to the steering servo and brake motor? And then the motor controller to the motor? Or do we need a seperate motor controller for the brake motor? If so, can both motor controllers communicate with the one arduino?

You will only need one Arduino for the project. But you will need a separate motor controller for each motor. (Except for a servo, which has its own internal controls.) The Arduino can receive the signals for the steering, brake and speed, sort them out, and send them to the appropriate controller. That's what I am doing for our car, and it works well.

So you need a motor and controller for each of three functions: steering, brake and speed. Here's my thoughts.

Steering: You mentioned a servo for steering. If that has enough torque, that would be great. If not, we are using a windshield wiper motor with a Pololu jrk 12v12 motor controller. That works great for us on a car, but might be overkill on a go-cart.

Brake: Here again, a servo would be great if it works. If not, a windshield wiper motor or power window motor would work fine, with a suitable motor controller. One of the Pololu Simple Motor Controllers might work, but they do not have current control and I burned one out on a windshield wiper motor.

Speed: Something like this should work fine. http://www.electricscooterparts.com/speedcontrollers36volt.html You can simulate a Hall-effect throttle with a digital potentiometer that has a SPI interface with your Arduino.

Again, good luck with the project. I'll be interested to see what you come up with.

[Robotics12]

thankyou for the help