interface circuit with computer

[mridang_agarwal]

okay....im a software developer so i n\have absolutely NO idea about hardware..anyways i want to make this porject an i need u help...okay i want to connect 8 thermocouple (tempereture sensors), 8 relay switches, etc.... i want to read in data from the thermocouple and control the relay switch accordingly...i want an option to expand my circuits later on if required...like 12 relays and 12 thermocouples...how would i do things....i knows there a a lotta electronic gurus out there....

[IanP]

There are 2 ways of doing this:

1. You can buy a PCI, ..., (depending on your computer hardware) A/D card with, say 16 analog inputs and 16 Digital I/Os.
Cards usually come with drivers for LabView or any other data acquisition software and as software developer you will be able to get data from Thermocouples, control relays etc.
Main disadvantage: cost.

2. You can bild a microcontroller based interface card (8051 family, PICs,....) and fit this card with A/D and DI/O ICs.
You will have to write a piece of software for this microcontroller and you will be using the RS-232 serial port for communication.
The most effective here is so called command-response protocol: the PC sends command to microcontroller, command is executed and microcontroller sends back response with data from ADCs and/or confirmation of the stage of the RLYs.
In this approach you are master of the system and you are unlimited with resources as you can expand your DI/Os by adding another IC with inputs/outputs (such as for example 82C55 : 24 digital I/Os) etc.

[MP]

There is a third option:

build your own card which communicates through the parallel port. You do not need a mirocontroller to communicate with this port.

The parallel port, for example, has inputs that you can access with an A2D chip such as the 8 channel/8 bit ADC0809. A person with programming experience such as yourself should have no problem pulling in the data. You could write a much nicer program more suited to what you are doing rather than use a generic program that is already packaged.

MP

[mridang_agarwal]

im sorry if you find me an idiot but please could give me the necessary circuit diagrams to build this....i have absolutely no idea about electronics...i prefer the second option:

". You can bild a microcontroller based interface card (8051 family, PICs,....) and fit this card with A/D and DI/O ICs.
You will have to write a piece of software for this microcontroller and you will be using the RS-232 serial port for communication.
The most effective here is so called command-response protocol: the PC sends command to microcontroller, command is executed and microcontroller sends back response with data from ADCs and/or confirmation of the stage of the RLYs.
In this approach you are master of the system and you are unlimited with resources as you can expand your DI/Os by adding another IC with inputs/outputs (such as for example 82C55 : 24 digital I/Os) etc. "

[MP]

Please continue this in the microcontroller area if it has turned into a microcontroller project.
Thanks
MP

[IanP]

As Moderator said this will be last post on this subjet here.

Please try this link http://www.kmitl.ac.th/~kswichit/
There you select type of microcontroler family you are interested in and you will find complete projects on how to build development cards with DI/Os ADCs...etc

[trigger]

Here is some examples in interfacing RS232 and parallel port on PC:

http://www.beyondlogic.org/