We are doing component sourcing for many years now and we supply all types of microcontrollers. Through ROBOT.LK, we don't have any intention to sell products or earn money. But we will popularise our company, product & services and provide as much as information to bring you the best quality product for a reasonable price. Okay I was informed by SevenZero about this topic and here is my answer to you.
1.Can we select good/original MCU?
Since we are a component vendor, to sell our product, we can also tell these
But in reality there is't anything called good or original in the world of components. However there is something called classing and equivalents.
If I be more specific, there are few classes of electronic components. Class A, Class B, Class C and sometimes Class D.
Class A is for production quality manufacturing. These components are going through a process to check each individual component for errors. So Class A is guaranteed to be 100% error free. class B is generally error free not guaranteed to be 100%. And Class C components are never going through an electronic test (E-TEST) other than a quick test to confirm their physical appearance. Class D is not even going through that process so you might find abnormal shapes on physical appearance.
Class A is mostly triple the price of Class C and Class B is double the price of Class C. Class D is very very cheap but nobody buys them so usually re-entered to machines for recycling or else dump as waste.
If someone with money goes to China and buy components from open market, that is usually Class C unless otherwise specified. Unfortunately, most of the sellers in Sri Lanka lack knowledge. They just buy and sell. They don't know anything about these and easily get played out.
We have a policy to import only Class A microcontrollers and components. We are a customer oriented company. So you can buy microcontrollers in Sri Lanka from us with confidence. We will not just sell and forget you. We will give you guidance, etc... to help you out.
If you buy components such as LM7805 from Pettah, check the output with the same multimeter. You will find one is outputting 5.095 and other 4.094. That is because they are class C. There is no marking or anything on the component but this is what you can expect. However, this is usually tolerable for hobby projects, but not for production quality professional designs.
With regard to equivalents.... If you tale TLV1117 and AM1117 are equal in characteristics. Just slight differences, but from different manufacturers. TLV one is expensive and AM one is less. You will find the same IC from LM (National Instruments) and from ST (SGS Thompson). So those are mostly charging for their brand name and reputation.
2.How we identify original/good Microcontroller from local market?(This two MCU have "Microchip" logo.)
Even we can't do that after decades of experience. Only thing is you need to buy from a trusted vendor. Especially a place where you find people with knowledge in electronics.
3.Why reason for this large variant of price of PIC18F2550 ?
This is the point. I'm almost sure this is the same IC. One is a reasonable vendor and other seems like having less business or no need to exist in the field. Our policy is to sell electronic components with a reasonable profit, so you guys can learn the subject and come to the field.
4.What is prize of original PIC18F2550?
Since the dollar has come up from Rs. 113 to Rs. 131, the current wholesale price is Rs. 550. It will be like Rs. 50 for postage if we have to post it to you. Class A is guaranteed
. We import Microchip & Atmel products only from USA and other components directly from factories in China, Hong Kong, Singapore and Thailand.
However, the guy who's selling the IC for Rs. 650 seems reasonable to me. Since you can get it quickly from him, it is good for you too. Please tell him about us so he can directly buy from us next time without wasting time.
Something else to tell you... Do you know that you need to use a different compiler if you use PIC18F series? With 12F, 16F HI-TECH C compiler you can't do that. So be sure to use HI-TECH C PIC18 compiler.