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Author Topic: Sensor / Actuator interfacing through serial port  (Read 967 times)
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Chennai, India
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I want to control a solenoid valve, read LM35 & a variable potentiometer from a computer through serial port all without using a microcontroller. How can this be done? Is this possible?
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from a computer through serial port all without using a microcontroller.

Seeing this forum is dedicated to using a micro controller and one specific one at that maybe your question is not best placed on the board.

You will have to attach an A/D with an asynchronous output and then control it. Using a serial port you can use the control lines input and output to drive a multiplexed input / output type port.
I did this many years ago for a computer and called it a PUP - Pseudo User Port.
The schematic is here:- http://www.doc.mmu.ac.uk/STAFF/A.Wiseman/Acorn/RTR96.html
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Thanks mike... As always you've replied.  Should let you know that your replies have been of great value in learning things. BTW, I feel comfortable posting questions here in the arduino forum than anywhere else..I dont know why...perhaps a sense of belonging i suppose smiley-wink

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the link is broken

cheers,
prakash
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the link is broken

Yes I just tried it myself. It is my old university and sometimes it is down but this is only temporally. If you don't manage to get it in a day or so send me a personal message and I will post it to you. I can't do it now as I am at work and don't have access to the files.

By the way I designed that one while I was sitting up in hospital.  smiley-wink
« Last Edit: October 12, 2009, 06:07:07 am by Grumpy_Mike » Logged

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@pracas

you need some intelligent circuit to read and convert the sensor data to a digital signal in order to send it over the serial port.

Instead of using an A/D converter and a multiplexer why not using a small arduino board? I.e the small RBBB (Really Bare Bones Board), http://moderndevice.com/RBBB_revB.shtml

Is there a reason not to use a microcontroller with digital and analog input ports.

In any case you need an external interface to get the signals into you computer.
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Well, I can use an arduino board and was demonstrating this to a student using the arduino board however i was stumped by a question as to 'well whats the point in using a computer if you are also using a microcontroller. Isn't there some kind of redundancy?'. I think its a valid question and wanted to see if there was a way to do it. So i'm here.


Cheers,
Prakash
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The only redundancy is that we use 2 intelligent devices, the computer and the microcontroller with the external sensors.

Both devices work together - the microcontroller collects the sensor data and sends it over the serial port to the computer.

The question is: do we need the computer?

The computer is the presentation part to display the status and the sensor data. Actually you don't need the computer. If you connect a display and some input elements, i.e. buttons, switches, you can implement a stand alone microcontroller board.

Please can you describe how do you want to use the computer to control the external components.
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Way back in the mists of time when I left school there were no personal computers or micro controllers and that sort of thing is what electronic engineers did for a living. So you can get rid of both if you want.

However, nowadays it is easy to use a computer as it is much more flexible when you want to change how something is done.

Time was when you would do this with just a computer and user ports or printer ports, but then operating systems took over and deliberately made it difficult to access the hardware. Then the mighty USB took away serial and parallel ports so making it mandatory to have some intelligence at both ends of the cable.
« Last Edit: October 12, 2009, 07:43:01 am by Grumpy_Mike » Logged

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Ok...I've been doing it without the computer a lot and its ok. Now, The project in context here is an internet based control & monitoring. I know this can be done with the Ethernet shield however there are 2 main factors hindering this - 1) non-availability of ethernet shields here 2) cost of an ethernet shield.

but then its still better to know how to access and control from a computer just for the knowledge sake and to be able to handle such questions from students in the future. smiley-wink

Mike,

It works now.  Lot of interesting stuff in there. Thanks a ton.

Cheers,
Prakash

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Well, I can use an arduino board and was demonstrating this to a student using the arduino board however i was stumped by a question as to 'well whats the point in using a computer if you are also using a microcontroller. Isn't there some kind of redundancy?'. I think its a valid question and wanted to see if there was a way to do it. So i'm here.
Sometimes the best answer to a question is another question:  Why does this PC have separate processors in the keyboard and video card?  Why not just use the PC CPU?

If the student can answer this question correctly, they should understand the benefit of using a microcontroller.

-Mike
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lol mfm.... thats a good technique... but when u want to create curious learners you need to be up one step ahead... :smiley
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