info about Stamp PLC

farsad

Hello,

I am a graduate student. I am developing a controller-data logger system for my project. I am thinking about using a parallax stamp PLC for my system.

can any body kindly answer these questions?

1. the PLC has only 4 analog inputs. is there any way to increase them to at least 6?

2. I want to use the PLC as a data logger too. how much is its memory size?

3. is there any A/D converter module among Parallax products ? I mean something that can convert an analog signal from a sensor to a digital signal so that I can use a digital port for reading an analog sensor?


thank you very much,

PS: sorry about my last Post. I forgot the to write the subject

stamptrol

By using several simple techniques, you can expand the inputs/outputs to any reasonable number. The technique generally uses a 74HC595 and 74hc165 shift registers to allow a few stamp pins to read many signals. Go to the Parallax store website and download the text "What's a microcontroller?" It has many sample programs to get you going.

Similarly, you can multiplex the a/d channels or use a multichannel a/d chip. Linear Technologies makes a whole family that will work with Stamps. The standard one I use is a 12-bit 2-channel LTC1298.

Rather than the Stamp PLC, I'd recommend a Stamp chip (from experience I'd use a BS2sx or BS2px) and a Super Carrier board ( #27130).

Large-scale data storage on-chip is not too practical; use an external memory unit such as a VDrive which will let you store data in a USB thumb drive.

Cheers,

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Tom Sisk

http://www.siskconsult.com
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farsad

i have the "What's a microcontroller" book. can you tell me where is the techniques for expanding the inputs/outputs numbers. i could not find them.

i am not very familiar with electronics. one of my friends has made me a a/d converter and amplifier. i can connect it to my basic stamp and read analog signals. the problem is that i need to have more ports for more analog sensors. the sensors are all the same.

your solutions are very general are very promising but i need a detailed circuit design and the program codes (just like parallax text books).

do you know where i can find this kind of information?

thank a lot,

Farsad

Mike Green

The StampWorks Manual is a good reference for this. Try Experiment #23 and #24.

You can find this and the matching source files here: www.parallax.com/Store/Sensors/CustomKits/tabid/134/txtSearch/stampworks/List/1/ProductID/144/Default.aspx?SortField=ProductName%2cProductName.

farsad

thank you Mike. as usual that was a great help. but what about expanding the analog ports?

i have made an a/d converter circuit for each of my sensors and i read them with shifin command. can I still use the expanded digital inputs as regular inputs? (i don't think so!) how should i write the code? do you have a sample program for reading the expanded analog inputs?

thank you much again,

Farsad

stamptrol

Another set of examples regarding expanded i/o is in the Stampworks text available from the Parallax website. Page 130 shows how to use the 74HC595 (expanded outputs)and page 137 shows how to use the 74HC165 (expanded inputs).

I recently used the 74HC165 circuits to give 20 additional inputs at the expense of 3 or 4 Stamp pins.

Sample programs are shown as well.

Cheers,

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Tom Sisk

http://www.siskconsult.com
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Mike Green

The StampWorks sample code shows how to use the digital I/O expanders. They don't appear as additional normal digital I/O pins.

Unfortunately, the PLC, although nicely packaged for industrial control, is limited in how it can be expanded. The Stamp's digital inputs and outputs have protective isolators which make it difficult to use them as bidirectional I/O pins which you would need to attach most external ADCs. The optional built-in ADC, although it has 8 analog inputs, only uses 4 of them and there's no provision for using the other 4 without modifying the circuit board of the PLC.

Chris Savage

Farsad,

Your duplicate post was removed. In the future please do not repost if you make a mistake. Instead click the pencil icon at the top right of the message and edit your post as necessary.

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Chris Savage
Parallax Engineering