 OT: 555 timer... need a hand with Astable settings :), been a long time... |
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| Mueller |
 Oct 2 2006, 04:05 PM
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914 Freak!  Group: Members Posts: 17,155 Joined: 4-January 03 From: Antioch, CA Member No.: 87 Region Association: None 
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okay, so I have a device I want to turn on for 10 to 20 seconds via the output going to a relay, off to be a few seconds.
I just downloaded pspice student version to see if I can mimic the circuit which I am not sure if the student version can do so..... using a kit from Ramsey http://www.ramseyelectronics.com/downloads/manuals/UT5.pdf other res. I have on hand are 1M (variable), a couple of 100K and a bunch of 1K....for extra caps, 100uF is the max |
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| davep |
Oct 2 2006, 06:46 PM
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914 Historian Group: Benefactors Posts: 5,292 Joined: 13-October 03 From: Burford, ON, N0E 1A0 Member No.: 1,244 Region Association: Canada  |
Some of the datasheets are flakey also. I forget which one, but a BIG name supplier didn't have a resistor in the discharge to ground that would limit the current to a reasonable value. You use a big cap and it would fry the chip since the current was unlimited; ie: a direct short to ground. The CMOS versions are very current limited. Don't forget the diode across the relay solenoid to kill the turn-off spike, that would cause flakey behavior if not included.
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Posts in this topic
Mueller OT: 555 timer... need a hand with Astable settings :) Oct 2 2006, 04:05 PM
Tom Mueller,
If I remember right you find time in ... Oct 2 2006, 04:24 PM bd1308 thats why it may have helped to put the output int... Oct 2 2006, 04:47 PM
jkeyzer Hey Mike,
The 555 datasheet has a reference circu... Oct 2 2006, 04:58 PM jsteele22 Hey Mike,
Here's a datasheet for the LM... Oct 2 2006, 05:04 PM Mueller google and ye shall find :)
555 timer calculator.... Oct 2 2006, 05:26 PM |
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