** Question: Expand “18” Potentialmeter by using 74HC595 or 74HC165? **

efly

Hi all,
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I have a control project which need to input total 18 numbers of potentialmeter at the same time, at first I am thinking using chips set (74HC595 & 74HC165) I/O expansion method. <Picture 01>
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However, after I connected all circuit I really don’t have any idea since the general RCTime· Porgram at first set Pin 7 to high (as a output) then in RCTIME line command consider Pin 7 is input, how can I mix the (Pin7e-after expand, for example)·as 74HC595 is input and 74HC165 is output at the same time….?
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Could some Parallax experts have any good idea?

Many thanks.··

Efly

Post Edited (efly) : 6/28/2009 5:01:17 PM GMT

Mike Green

I don't recommend reading potentiometers this way since it's very slow and will require a lot of parts. The 74HC595 and 74HC165 are very good solutions for digital inputs and outputs. I suggest you use some kind of multiple channel analog to digital converter like the ADC0838 (8-channel). Assuming your potentiometers are relative high value (4.7K to 10K), you just connect them across the +5V supply and connect the tap / slider to the ADC input. There's plenty of sample code showing how to use this device with a Stamp. You'd need 3 of them for up to 24 inputs. They're less than $3 each. You can use the same I/O pins for the clock and data lines and have one dedicated I/O pin for the select line for each device. That's only 5 I/O pins.

Here's some info: psurobotics.org/wiki/index.php?title=ADC0838

Do a web search for "ADC0838 Stamp" for other info

Post Edited (Mike Green) : 6/28/2009 5:36:43 PM GMT

efly

Dear Mike,

Thanks for your valued advice, I will do some study on ADC and hopefully will suceed.·

Efly

efly

Dear all,
I found that it might help to using 8-Channel 12-Bit A/D Converter (MCP3208) in order to reduce the Basic Stamp input pin number for above project, however, does anyone have any sample circuit connection diagram between Basic Stamp 2 and·MCP3208 since I cannot find it on the parallax page as it only provide the datasheet detail.
http://www.parallax.com/Store/Components/AllIntegratedCircuits/tabid/154/List/1/ProductID/573/Default.aspx?SortField=ProductName%2cProductName
Many thanks.··
Efly

dev/null

You might consider TLC1543 10-bit ADC. 11 analog inputs.

Sample code attached.
The .VSD file is a Microsoft Visio file I made for the schematics, but the datasheet is pretty clear on this.

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