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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...

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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.
First comes the hardware, then the software.
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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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