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View Full Version : A Better robot control Board ( Proposal )



vikas
02-04-2011, 12:06 AM
Was just looking around for good high performance robot control boards in India , and like always most are just copies of each other So after doing some research ive come down to this config -

Controller -
dsPIC33FJ64GS606 (http://www.microchipdirect.com/ProductDetails.aspx?Catalog=BuyMicrochip&Category=dsPIC33FJ64GS606&mid=1&treeid=8) - http://www.microchipdirect.com/ProductDetails.aspx?Catalog=BuyMicrochip&Category=dsPIC33FJ64GS606&mid=1&treeid=8

2 x QEI ( Exact dead reckoning at no overhead )
12 PWM channels ( 2 are used for motor )
64 KB Flash and 9 k RAM
64 TQFP ( Enough IO )
40 Mips ( Decently Fast )
2x Uart
5$ low Qty

Hbridge -

TB6612FNG (http://www.robotshop.com/pololu-dual-dc-motor-driver-1a-4-5v-3-5v-tb6612fng.html?utm_source=google&utm_medium=base&utm_campaign=jos) - http://www.pololu.com/catalog/product/713

MOS
1.2 A DC , 3 A Peak per channel
Internal fly backs
< 2$ low qty
2 such chips in prallel config will power 2 motors allowing upto 2 A DC / motor and 6 Peak per motor

This will be availbile on something like these lines -

http://www.pololu.com/catalog/product/775

But i think a robot kit should be wirelessy programmable ... maybe a simple RF for programming and communication built in. Itll be easier to program and all sort of sensor data / reading are instantly available to you.

Any suggestions for improvements , before i start drawing ?

avinash_g
02-04-2011, 09:20 AM
Just note one point that out of 8,16, and 32 bit MCU from Microchip. It would recommend the 16 bit least. The reason is that a free compiler is NOT available. You will say Microchips own compiler is there, but I think it does not has the commercial usage free. The best compiler I found for PICs is the HI-TECHs compilers. No the company is owned by Microchip itself. HI-TECH free compiler for PIC16 and PIC32 bit MCUs but not for 16bits or DSCs. The advantage of HI-TECH compiler is that its all free, even for commercial use. Just few high end optimizations disabled, thats it it is the only limitation. Also HI-TECHs method of handling interrupts is far more clear and better than Microchips compilers. Also tricky linker scripts in Microchip Compiler make it more worse, this problem is not present in HI-TECH compilers.

For wireless programming go for Bluetooth (I am too working on It)

MohitM
02-04-2011, 12:11 PM
Avinash,

Microchip no longer recommends the Hi-Tech compiler for 16-bit PICs. See:
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en542865

And you can safely develop commercial applications with the free version of Microchip C compilers. For the first 60 days its the fully working version, and then some optimisations are disabled. But at 40 MIPS and 64 kB ROM, maybe the 'un-optimised' code won't matter much. I was at a Microchip conference, some years back, and somebody raised this point and also added that if you change the PC system date, the compiler goes back to the full version. The Microchip guy confirmed this, but didn't seem too objecting about the trick. Since Microchip compilers will only work with Microchip products, I don't think they are too perturbed. I think they see the software as a tool to increase their hardware sales.


Vikas,

Regarding the H-bridge:
Why don't you use 4 mosfets (2 p-channel and 2 n-channel) and drive them with the motor module of the dsPIC? The h-bridge can be implemented very conveniently and efficiently this way. The bridge can have high ratings (say, 50V and 10A) depending on mosfets used. You could also look into TC4469 from Microchip to implement an h-bridge driven by two PIC pins.

allbits
02-04-2011, 02:59 PM
I am working on a hi end board right now, and I would recommend you give headers for PIMs (Like in explorer 16 board) so that any chip can be plugged in. Wireless programming will make it a hit, and it is easy to implement it. Would support Mohits View on H bridges. You can use surface mount packages to save space.

Also regarding compilers, I have both the student and the commercial version, and before purchasing the commercial version, I have been using the student version exclusively. Frankly, i could not see much difference, as I was not building up codes higher than around 16K. Above that, i do not know. Attending the Microchip masters conference is the best way to get the commercial versios free/or at a subsidised rate. Eventhough you will have to wait till oct/nov for that.

MohitM
02-04-2011, 03:49 PM
If you are hell-bent on the commercial version, you could talk to the Microchip regional head in Delhi. The office is in one of the towers in Nehru Place. Don't remember which one. Tell him this is for a low-cost robotics dev board and I'm sure they'll offer something like 30% off on the list price.

vikas
02-04-2011, 04:29 PM
Mos based hbridge in maybe higher end version , My target motors are micromotors / GM 12 motors. Small with small stall current max 1.5 A.

The idea is of a high end robo platform for research / competitions. More like high performance robotics platform for testing theories etc on. But this robot should BE FAST atleast > 1 m/s I sick of seeing snails, and with hardware capable of handling speeds ( hence dspic ).

I will posting a article on competition robotics , the second one i will be building a modular robot ( so final product will be like this only ), currently its based on polulu parts.

As for the compiler i might be selling hardware for educational purposes ( though i have plans to be Open source ), also the current compilers would do fine ... i dont really need super optimized code or anything.

vikas
02-05-2011, 05:45 PM
http://www.robotshop.com/droids-muin-dsnav-navigation-board-2.html

This looks like a nice board to get ideas from , though this is more of a motor controller board , not enough io left for sensors etc ...