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The Projects Forum Working on an electronics project and would like some suggestions, help or critiques? If you would like to comment or assist others with their projects, this is the place to do it.

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Old 02-21-2009, 04:48 AM
JeffreyNHouston JeffreyNHouston is offline
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Default Anyone know about the Exar XR-2240 Timer/Counter?

Hello Friends,

Does anyone know anything, I mean anything, about the Exar XR 2240 chip? I found a datasheet that makes it look like a good chip to make a sequential timing IC. It can time and count for up to 5 days, and then produce a monostable timing for an event like turning on and off a motor using RC.

It was discontinued by EXAR. Does someone make an equivalent? It is a 16 pin DIP.

From the datasheet:

The time base works as a multistable vibrator with a time period equal to an RC. The eight-bit counter can divide the time output by any integer value from 1 to 255. Generates accurate timing intervals from microseconds through several days. Counter outputs are open collector and may be wire or connected.

Any leads or information would be greatly appreciated. I have been working on a 555 monostable, triggered by a digital pool clock for the days to next monostable event. It would be great to have one chip/circuit that triggers my monostable every day, or two days, or three days...

Jeffrey
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Old 02-21-2009, 12:02 PM
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beenthere beenthere is offline
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There are several useful IC's that have been discontinued from production. I'm not sure the 2240 was really dependable for 5 day timing, though.

It's a big step, but a $1.50 microprocessor can do those timing functions and more.
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Old 02-24-2009, 03:28 AM
JeffreyNHouston JeffreyNHouston is offline
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Thanks Beenthere,

$1.50? The 2240 chips sell for more... That is inexpensive.

I am openminded, but admitted ignorant. Willing to learn, but is there enough time to learn how to design a timing circuit and machine language?

I was going to write a Visual Basic program to calculate my RC values. After spending a few hours learning Visual Basic, I decided to just use a spreadsheet (only slightly more advanced that pushing calculator buttons).

If no one is producing chips like the 2240, I will have to get smarter/faster and learn the new stuff.

A microprocessor... Wow.
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Old 02-24-2009, 03:38 AM
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SgtWookie SgtWookie is offline
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Actually, they're cheaper than that.

You can get an 8-pin microcontroller from Microchip for less than $0.75 that runs off of 3v-5.5v at 4MHz without any external devices. Not bad, eh?
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