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Author Topic: Microcontroller (What kind should I use)  (Read 1058 times)

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Offline darthvader5500Topic starter

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Microcontroller (What kind should I use)
« on: April 19, 2010, 01:20:29 PM »
Alright, so I'm creating a robot for a school project. I want it to be a 4-wheeled robot that has 2 (or maybe 1) arms, and is controlled from my computer (via bluetooth). At first, I wanted to put a camera on it as well, but then I read how difficult that can be, so I might still put on the camera, but probably not (maybe if I have time...).
So yeah, its gonna be a 4-wheeled robot (wheels driven by motors) with 1 or 2 arms, and controlled from my computer via bluetooth, and I might add a few sensors. The chassis is roughly car-like.
So, what kind of microcontroller should I use for this kind of robot? What functions does my microcontroller HAVE to have?
Also, any additional tips on my robot are appreciated.

Offline corrado33

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Re: Microcontroller (What kind should I use)
« Reply #1 on: April 19, 2010, 02:28:44 PM »
Well, if you're going to use four MOTORs, and not servos, you're going to need at least 4 PWM ports.  The AtMega8 (the MCU we usually suggest for beginners) only has three.  Also, depending on how you control the arms, you might need more, but probably not.  Other than that, everything (except the camera) can be achieved with most MCUs.  I really don't know about the camera, someone else will have to chime in.  It all depends on the number of inputs you need. 

Offline darthvader5500Topic starter

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Re: Microcontroller (What kind should I use)
« Reply #2 on: April 19, 2010, 02:54:27 PM »
Well, if you're going to use four MOTORs, and not servos, you're going to need at least 4 PWM ports.  The AtMega8 (the MCU we usually suggest for beginners) only has three.  Also, depending on how you control the arms, you might need more, but probably not.  Other than that, everything (except the camera) can be achieved with most MCUs.  I really don't know about the camera, someone else will have to chime in.  It all depends on the number of inputs you need.  

I'm gonna try to have 2 motors (2 wheels per motor), but if that doesn't work, I'll go for a motor for each wheel. And btw, the arms will be controlled by servos. They'll probably be 3 DOF.

Offline darthvader5500Topic starter

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Re: Microcontroller (What kind should I use)
« Reply #3 on: April 19, 2010, 03:02:37 PM »
Well, if you're going to use four MOTORs, and not servos, you're going to need at least 4 PWM ports.  The AtMega8 (the MCU we usually suggest for beginners) only has three.  Also, depending on how you control the arms, you might need more, but probably not.  Other than that, everything (except the camera) can be achieved with most MCUs.  I really don't know about the camera, someone else will have to chime in.  It all depends on the number of inputs you need.  

I'm gonna try to have 2 motors (2 wheels per motor), but if that doesn't work, I'll go for a motor for each wheel. And btw, the arms will be controlled by servos. They'll probably be 3 DOF. And what about the bluetooth? I need UART for that, right?

Offline corrado33

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Re: Microcontroller (What kind should I use)
« Reply #4 on: April 19, 2010, 03:40:44 PM »
Yes I believe you need UART for bluetooth, but I can't speak from experience.  I think all AVR MCUs have UART, PWM, and plenty of other functions that you'd need.

Offline MangoBot

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Re: Microcontroller (What kind should I use)
« Reply #5 on: April 19, 2010, 06:47:34 PM »
another question, i am planning on making a tricopter. The last motor(at the back) will turn using a servo. What would be a good microcontroller to use. I don't have any language preference, but a light weight one and one that is not too expensive would be best. It needs to run 3 motors, 2 servos, 1 ultrasonic rangefinder, and the accelemoters/gyros(not sure how many, also a good thing i would like help with)to run it.

Offline Soeren

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Re: Microcontroller (What kind should I use)
« Reply #6 on: April 19, 2010, 08:28:21 PM »
Hi,

I'm gonna try to have 2 motors (2 wheels per motor), but if that doesn't work, I'll go for a motor for each wheel.
Why wouldn't that work?
With a differential, you could make do with a single motor.
R/C ball diff's, in which you can dial in the degree of lock, are not exactly cheap though, but they do remove the issues of different power vs. speed that may apply when using 2 (or more) motors - and the Cool Factor...  ;D
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline Soeren

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Re: Microcontroller (What kind should I use)
« Reply #7 on: April 19, 2010, 09:29:17 PM »
Hi,

another question,
Should go in another tread!


What would be a good microcontroller to use. I don't have any language preference, but a light weight one and one that is not too expensive would be best.
Distributed processing with a number of PIC10F2xx would perhaps make life easier for you.
They're the lightest controllers on the earth when you choose the 6 pin SOT-23 housing (like a regular SMD transistor, just with 6 pins). You have 4 pins free (power and ground takes 2), so either each of them can handle a couple of tasks or each can do just one thing and use the rest of the pins for comms to the master controller.

One downside to them is the lack of 16 bit timer, but the '222 comes with 2 A/D-Cs.
Next step up in size will probably be the µmy form factor, but IIRC, both the ATtinys and the 8 pin PICs come in SOT-8 as the smallest.

Fairchild did some really tiny controllers, but they folded the production some 5 years ago and I don't know if they're around in smaller numbers - too bad, cause they were quite clever and very small (and too bad the complete set of programmer, hardware simulator, adapters for the surface mounted variety and what not for those little gems won't do any good on any other controller family - Well, win some, loose some, add expensive equipment to "pluck bin" once again).

Now I don't know what you call light weight, but most surface mounted chips should fit the bill if you have just a little motor power left over. The copper in the wiring will be a larger factor, so serial comms should help there, or conductive sewing tread anywhere the resistance is OK if you're hard pressed. PCB material can be had in very thin versions (without going to foil PCB) etc., but giving they'll be a very small percentage of the battery, it's probably not worth going to extremes.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline Admin

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Re: Microcontroller (What kind should I use)
« Reply #8 on: April 20, 2010, 09:54:38 AM »
Quote
a 4-wheeled robot (wheels driven by motors) with 1 or 2 arms, and controlled from my computer via bluetooth, and I might add a few sensors.

Something like this?
http://www.societyofrobots.com/robot_ERP.shtml

Offline darthvader5500Topic starter

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Re: Microcontroller (What kind should I use)
« Reply #9 on: April 20, 2010, 10:38:32 AM »
Quote
a 4-wheeled robot (wheels driven by motors) with 1 or 2 arms, and controlled from my computer via bluetooth, and I might add a few sensors.

Something like this?
http://www.societyofrobots.com/robot_ERP.shtml


hmm... maybe... but less complex, of course, and it won't have everything that robot does. I might post a schematic or something later.  
« Last Edit: April 20, 2010, 10:41:20 AM by darthvader5500 »

 


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