Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!yale!mintaka!mit-eddie!rutgers!galaxy.rutgers.edu!argus!ken From: ken@argus.UUCP (Kenneth Ng) Newsgroups: sci.electronics Subject: Re: XR-2240 Keywords: XR-2240 Message-ID: <1617@argus.UUCP> Date: 12 Mar 90 13:59:59 GMT References: <3687@tukki.jyu.fi> Organization: NJ Instit. of Tech: TEIES Project Lines: 39 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.edu