Help me understand this LF robot schematic

[hiyan]

iam biggner in Robot me and my friend wantto make this Robot but iam little bit confused this schematic like 7805 circuit connected with micro controller of which part ?2nd when we apply required voltages will it work or will it connected to computer then it work?

Thanks

 

[taitsoft]

Re: schematic problem

iam little bit confused this schematic like 7805 circuit connected with micro controller of which part ?2nd when we apply required voltages will it work or will it connected to computer then it work?

That line-following robot does look like a fun project.

I really don't want to dampen your enthusiasm for building it, but if you are confused by what you see there do you really think it's a good project for you and your friend? I see the designer's email address is attached to the schematic so if you are determined to go ahead perhaps you can get help directly from him.

I'm not sure I fully understand what confuses you so I'll just try to describe what I see there. The schematic is broken up into three distinct sections: 1) the microcontroller and motor-driver chip; 2) the power supply based on some NiCd batteries and a 7805 voltage regulator; 3) a set of four IR sensor circuits.

The NiCd supply is connected directly to the motor chip and the 7805 is used to provide a regulated 5V supply to the microcontroller and the op-amps used by the sensor circuits - just think of everywhere marked "+5V" as being connected together.

All the parts are fairly standard. The microcontroller used is an Atmel flash memory chip based on the 80C31 architecture:

http://www.atmel.com/dyn/products/product_card.asp?part_id=1938

The motor driver chip datasheet is here:

http://www.st.com/stonline/products/literature/ds/1330/l293d.pdf

and the op-amps are described here:

**broken link removed**

There are only two problems with the electronics for me (the mechanical details are another story!). One is that the author has not specified part numbers for the infra-red emitter/photo-transistor pairs; not much of a difficulty really, but it would slow me up a bit as I would need to experiment with different choices for these parts. The other bigger problem, for me at least, is his choice of microcontroller. If I wanted to replicate this circuit exactly I would have to expend a lot of effort in getting all the software and hardware needed to program this device. That wouldn't be an issue if pre-programmed chips were available but it is not clear that this is the case here. Actually, it would not be too difficult to use a different type of microcontroller (PIC or AVR say) because the author has written the main program in C rather than chip-specific assembler. If I did that though I would write a new program from scratch.

In answer to the second part of your question, once built, the robot does not need to be connected to a computer as all the intelligence is in the microcontroller. You would only need a PC to download the compiled version of the author's program (robot1.hex) to the microcontroller. You wouldn't need a computer at all if you could get hold of a pre-programmed AT89C2051 or could get someone to program the chip for you. However, I think you would miss a lot if you were unable to program the chip yourself - being able to modify the program is half the fun of a robot project.

Before I finish, I'd like to show you another, superficially similar but actually more sophisticated line-following robot; it's tiny and really very sweet:

**broken link removed**

Please don't take this the wrong way as I have no idea what your experience level really is, but maybe you and your friend would be better off starting out with a robot kit where all the parts are supplied. One of the members of this forum (blueroomelectronics) has a company making stuff like that:


**broken link removed**

I hope this info helps you a bit.

David

 

[hiyan]

Re: schematic problem

iam so Thankful to you and my friend also .your post give us a chance to do experiment with it but again tell me the transistor number with attached with LEd and what kind of photo diode used in this project wich you mentioned in your link and what is isp which have 6 pins?

Again bunndle of THanks .

 

[taitsoft]

Re: schematic problem

... but again tell me the transistor number with attached with LEd and what kind of photo diode used in this project wich you mentioned in your link and what is isp which have 6 pins?

The tiny robot I mentioned was made by a Japanese experimenter (I think) and he no doubt used items readily available in Japan. However, I can't find a source of the SPI-315-34 photoreflectors he used in this part of the world (UK). A little investigation shows they are made by Sanyo. The only datasheet I could find is written in a mixture of Japanese and English and it can be downloaded from this Romanian web site:

http://www.tranzistoare.ro/datasheets/700/500222_DS.pdf

My local distributor stocks items in this range:

**broken link removed**

and perhaps the project could be adapted to use these parts. Alternatively, it might be possible to make your own workalikes with separate emitters and detectors just like the design by the Thai student. Of course, you could be lucky and find a local source for the SPI-315-34.

Your second question about the ISP connector is easier to answer. The microcontroller in this robot is programmable multiple times (it uses flash memory). If you look at the picture you'll see that the microcontroller is wired into the circuit and it would be very difficult to remove it for reprogramming with a traditional programmer. The connector allows the chip to be reprogrammed without unsoldering it (a great convenience). ISP stands for "In-System Programming" or "In-System Programmer". You can learn more about ISP and the microcontroller used in this robot here:

http://www.atmel.com/products/AVR/

There are lots of web pages where robots are described by their proud owners, but often reproducibility is low on the designer's list of priorities if they even thought of that aspect at all. As you get more experienced you can pick and mix the ideas you find or, better still, become creative yourself. As a beginner though you should seek out designs which can be made with easily obtained materials, ones that do not need specialized equipment to build them and ones that do not leave a lot to your ingenuity (or lack of it). There are at least two ways to do that: the first is to buy a kit as I suggested previously and the second is to join a local club where there will be a lot of help available and perhaps a tried-and-tested club project. Good luck!

David

 

[hiyan]

Re: schematic problem

Thanks .if there is any club and guidance inst in my country definately i join but no info in big level are available so i concerned with this site i got alot of info .Thanks