ken@argus.UUCP (Kenneth Ng) (03/12/90)
In article <3687@tukki.jyu.fi>, sm@tukki.jyu.fi (Seismo Malm) writes:
: Can anybody help me with XR-2240 Timer. The pinout is
: following
: It was the only timer capable to produce delays of 100 sec
: availlable from local electronic store and they don't have Exar
: datasheets. I guess, that I should connect pins 8&10 and put timing
: resistor between pins 13&15 and timing capacitor between pins 13&9?
: Triggering is by positive pulse to pin 11? Am I right?
One of my first electronics projects was the XR-2240! After I found out
that a 555 isn't too good for an 8 hour delay. See if you can find the
magazine Radio Electronics, July 1978, page 61-65. It is on the XR2240,
XR2250, and XR2260. Timing is done with a resister between 16 and 13,
with a cap between 13 and ground. Trigger is positive pulse to pin 11.
In the examples, they have a 20K resister between 15 and 14, something
about a stable time base. The output pins are open collector pull up type.
How it works is kinda as follows: you have a 555 oscillator tied to an
8 bit binary counter. If the oscillator has a cycle time of 1 minute,
output pin 1 will have a cycle time of 1 minute, pin two 2 minutes, pin
three 4 minutes, pin four 8 minutes, up to pin 8, with a cycle time of
128 minutes. For your delay in minutes, 'or' together the pins you
want to add up to the required delay. Attach it to a 10K resister that
is tied to V+. When the output line goes high, then the time delay you
want has occurred. Notes: if you measure the output voltage, you'll see
that it increases kinda like a binary ladder, so you'll need a threshold
on the output detect circuit (something I overlooked). Also note that
I last used this beast in 1980, so my memory is foggy at best. I'm actually
a bit surprised I was able to find the article. Good luck.
: Thanks.
: Seismo Malm sm@tukki.jyv.fi
PS: the sample circuit I have also has a 0.01 microfarad cap between pin
12 and ground.
--
Kenneth Ng: Post office: NJIT - CCCC, Newark New Jersey 07102
uucp !andromeda!galaxy!argus!ken *** NOT ken@bellcore.uucp ***
bitnet(prefered) ken@orion.bitnet or ken@orion.njit.eduhenry@utzoo.uucp (Henry Spencer) (03/16/90)
In article <1617@argus.UUCP> ken@argus.UUCP (Kenneth Ng) writes: >One of my first electronics projects was the XR-2240! After I found out >that a 555 isn't too good for an 8 hour delay... Actually, if you want long delays and don't insist on using a single chip, much the simplest way to proceed is to build a reasonably slow oscillator with a 555 or whatever and then just run the output into a CMOS counter, e.g. 4040 or 4060. The counter's power consumption is negligible and the available counters go up to a division ratio of 2^16 or so. Their main limitation is that the division ratio has to be a power of 2. -- MSDOS, abbrev: Maybe SomeDay | Henry Spencer at U of Toronto Zoology an Operating System. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
ken@argus.UUCP (Kenneth Ng) (03/21/90)
In article <1990Mar15.171310.28917@utzoo.uucp>, henry@utzoo.uucp (Henry Spencer) writes: : In article <1617@argus.UUCP> ken@argus.UUCP (Kenneth Ng) writes: : >One of my first electronics projects was the XR-2240! After I found out : >that a 555 isn't too good for an 8 hour delay... : : Actually, if you want long delays and don't insist on using a single chip, : much the simplest way to proceed is to build a reasonably slow oscillator : with a 555 or whatever and then just run the output into a CMOS counter, If I were to do it now I'd probably use a 555 and a loadable count down timer. It'll be cheaper, easier to find the parts, and having a countdown display is kinda neat :-). But when your 12 years old, and see the wonder of electronics, the smell of rosin, and the thrill of seeing all those debugging LED's go on and off, the Simpson meters pulsating on command, the sexy shiny new integrated circuits; it's almost better than sex :-). -- Kenneth Ng: Post office: NJIT - CCCC, Newark New Jersey 07102 uucp !andromeda!galaxy!argus!ken *** NOT ken@bellcore.uucp *** bitnet(prefered) ken@orion.bitnet or ken@orion.njit.edu