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Electronics => Electronics => Topic started by: cata on October 17, 2010, 06:02:36 AM

Title: search after micro controller
Post by: cata on October 17, 2010, 06:02:36 AM
I search after a micro controller (I prefer PIC but it can be other like AVR …)
I want to control with this micro controller twelve different motors and twenty four micro switches that are not dependent
I need that the micro controller has sufficient I/O ports, PWM, memory to know the order of motors operations (what memory I need ROM / FLASH / EEPROM / RAM / SRAM … AND How I can calculate who much I need ?), A/D for 24 micro switches
Also I search after documents / sites / books that explain about micro controller, especially how to choose the right micro controller ?   

Title: Re: search after micro controller
Post by: DUKELancelot on October 17, 2010, 08:37:58 AM
Wow 24 ADCs I do not think there are any Micro Controllers that have that. Micro switches don't require ADCs.
And by motors you mean servos right? Because if you mean dc motors than you will have to have 12 H-bridges.


I would recommend the Arduino Mega It has 54 I.O and 16 ADCs. all for only 60$.

Plus It's made in Italy not China!!!!
Title: Re: search after micro controller
Post by: Soeren on October 17, 2010, 08:52:33 AM
Hi,

Quote from: cata on October 17, 2010, 06:02:36 AM
I search after a micro controller (I prefer PIC but it can be other like AVR …)
I want to control with this micro controller twelve different motors and twenty four micro switches that are not dependent
I need that the micro controller has sufficient I/O ports, PWM, memory to know the order of motors operations (what memory I need ROM / FLASH / EEPROM / RAM / SRAM … AND How I can calculate who much I need ?), A/D for 24 micro switches
You don't need A/D-C for microswitches, a digital I/O pin is what's used (although several microswitches could be read from a single A/D-C pin if needs be).
Microchip has recently rewamped their selection page, so you could go play with the parameters you want to include, buit one chip that'll cover your needs is the PIC18F87K90 (http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en547324) (in a 80 pin TQFP).

Key features of the PIC18F87K90
128k program memory
4k SRAM
1k EEPROM
69 lines of I/O
6  8-bit timers
5  16-bit timers
7  CCP's
3  ECCP's
2 UARTS
24  12-bit A/D-C's
3  Comparators
RTC
CTMU (a pulse timer)
Direct LCD drive (48 segments/192 pixels)
(Hardware) SPI and IIC


To calculate exactly how much you need, you need to plan it out on paper and to have a clear idea of how you wanna do it all - until then, it will just be guesswork.


Quote from: cata on October 17, 2010, 06:02:36 AM
Also I search after documents / sites / books that explain about micro controller, especially how to choose the right micro controller ?
The right microcontroller is one that you:
Are comfortable programming
Have programming tools for
Have the needed peripherals and I/O

Microchip has lots of documents (application notes, application briefs etc.) and Educypedia (http://www.educypedia.be/) has got a wide variety of tutorials of all kind - more than enough to keep you occupied for a while.

If you haven't worked with microcontrollers before, or have only touched upon them briefly, I would advice you to start of with something much smaller, as I don't think you have much chance of success with a large project like what you hint at.
Title: Re: search after micro controller
Post by: Soeren on October 17, 2010, 09:01:15 AM
Hi,

Quote from: DUKELancelot on October 17, 2010, 08:37:58 AM
Wow 24 ADCs I do not think there are any Micro Controllers that have that.
Among the PIC controllers:
13 controllers have got 32 lines of A/D-C
 2 controllers have got 30 lines of A/D-C
 6 controllers have got 28 lines of A/D-C
24 controllers have got 24 lines of A/D-C
Most of the above are 12-bits, the rest are 10-bits.
Title: Re: search after micro controller
Post by: cata on October 17, 2010, 08:44:00 PM
I think to use DC motors, but it isn't final decided.
I search after electronic servo control schemas
What are the features that the Arduino Mega has?
Do you know about projects that used more than 6 motor that was don't dependent ?
For 12 motors I think that I need only 6 H-bridges, am I right ?
There are a lot of micro controllers in the PIC18F series,
Where I can find a table that compares all the features in these series?
Title: Re: search after micro controller
Post by: rbtying on October 18, 2010, 12:42:55 AM
What is "electronic servo control schemas"?  A hobby servo is controlled by a pulse between 0.75 ms to 2.25ms every 20ms, with a linear interpolation for angle.  A DC motor with an H-bridge will only have speed control, based on your PWM output.  You will need an H-bridge per motor, but if you're buying H-bridges in packages, ie L298 or SN745510, or etc, you usually will get 2 H-bridges per package.  I don't know about the PIC stuff, but the Arduino Mega has these specs:
Code: [Select]
Microcontroller ATmega1280
Operating Voltage 5V
Input Voltage (recommended) 7-12V
Input Voltage (limits) 6-20V
Digital I/O Pins 54 (of which 14 provide PWM output)
Analog Input Pins 16
DC Current per I/O Pin 40 mA
DC Current for 3.3V Pin 50 mA
Flash Memory 128 KB of which 4 KB used by bootloader
SRAM 8 KB
EEPROM 4 KB
Clock Speed 16 MHz

I do wonder, though, what do you need 12 motors for? 
Title: Re: search after micro controller
Post by: Soeren on October 18, 2010, 07:09:27 PM
Hi,

Quote from: cata on October 17, 2010, 08:44:00 PM
I search after electronic servo control schemas
Not much schematics in that. All you need is a pulse on the signal line.
The standard is 1.0ms to 2.0ms (with the center position being 1.5ms) repeated each 20ms, but unfortunately, several manufacturers down give a damn about standards, so they float a lot and the outer bounds I have seen so far are something like 300µs (0.3ms) to 2.8ms - sad, but true.


Quote from: cata on October 17, 2010, 08:44:00 PM
What are the features that the Arduino Mega has?
It's an AVR based board (and in the words of Gill Bates... That's a bug, not a feature  :P ;D ;D ;D)
I thought you preferred PIC controllers?


Quote from: cata on October 17, 2010, 08:44:00 PM
Do you know about projects that used more than 6 motor that was don't dependent ?
I know English isn't your first language (not mine either), but please try to rephrase that line - it doesn't make any sense.


Quote from: cata on October 17, 2010, 08:44:00 PM
For 12 motors I think that I need only 6 H-bridges, am I right ?
Only if you keep half the motors for repairs ;)

If you only need the motors to rotate in one direction, you could (theoretically) drive 4 motors from a single H-bridge (if it could be used transistor for transistor). Many H-bridge chips are in fact half bridges, so you could drive and brake a motors from one half bridge, as long as you only need unidirectional rotation. If you need your motors to be bidirectional, however, you need one bridge for each motor.


Quote from: cata on October 17, 2010, 08:44:00 PM
There are a lot of micro controllers in the PIC18F series,
Where I can find a table that compares all the features in these series?
At MicroChip (http://www.microchip.com/productselector/MCUProductSelector.html)

Trying to build a biped?