How to wire two 555s in parallel?

bmachine

Jun 7, 2006
16
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Jun 7, 2006
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Hello.  Newbie here.

I read with interest the article by John Adams about using a 555 as a timer

I am trying to build a controller that would activate a relay in a "non regular" way.  In other words, when I use the astable example John gives, depending on the values used, the circuit will give me "on for 1 sec, off for 2 secs, on for 1 sec, off for 2secs, etc...".  This pattern repeats until power is turned off.  What I would like is to get an irregular pattern such as "on for 1 sec, off for 2.7 sces, on for 0.8 sec, off for 1.4 secs, etc..."  I am not too picky about the actual intervals, as long as it appears more random. 

I was thinking that I could run two 555s with one set for one timing (1 sec on and 2secs off for example) and then second one set for a different timing (1.6 sec On and 1.3 off for example.  I would then take these two outputs and combine them to get a more irregular pattern to trigger my relay.

My question is How do I combine these two outputs without getting overloads or feedbacks or whatever dangerous thing might happen if I simply connect them together before going to the relay.

Or maybe there is a better way to achieve this...

Any help would be greatly appreciated.

Thank you

Bmachine.

 

audioguru2

Apr 6, 2004
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Apr 6, 2004
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Two 555's cannot be paralleled, but Cmos inverters can.
Here is a circuit to randomly flicker an LED's light. Change its capacitor values to slow it down and maybe it will be OK for your application.

View attachment 39134

 

bmachine

Jun 7, 2006
16
Joined
Jun 7, 2006
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16
Thank you very much for the answer and the schematic Audioguru. 

At first the file wouldn't open so I found a link for it here (hope it's OK to post links):
http://members.shaw.ca/novotill/FireLightFlicker/index.htm

I will give that a try.

Bmachine.

 

hotwaterwizard2

Jan 8, 2004
2,022
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Jan 8, 2004
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2,022
How about this?

http://home.cogeco.ca/~rpaisley4/LM555.html

LM555Delays2.GIF


 
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