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Basic Electronics » 555 astable on breadboard

August 21, 2010
by egero1
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I am trying to wire up a 555 astable circuit. I have the schematic, but I am not sure how to convert the schematic for pins 2, 7, and 6 into something real on the breadboard. If anyone has a pic of what that would look like with the 2 resistors and the capacitor, I would appreciate it, or a website link that could point me in the right direction would be great.

Thanks, Eric

555 astable

August 21, 2010
by mongo
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What frequency are you looking at operating?

August 21, 2010
by egero1
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R1 is 100k and R2 is 4k ohms. C is 100 nf which I believe should give me something close to 75Hz?

August 21, 2010
by egero1
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R2 is 47k ohms, not 4k ohms. That was a typo.

August 21, 2010
by mongo
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Try R1 as 1K

R2 as 20K

C as a .47 uF

Should give you 74.8Hz at about a 50% duty cycle

Lower current draw and they are standard component values.

August 21, 2010
by egero1
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Thanks for the info. I will use these values instead. But, my real problem is hooking everything up. I have tried several different ways to hook up pins 2, 6, and 7 but I am not sure how to make these connections on the breadboard. Any suggestions?

August 21, 2010
by mongo
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Shat kind of bread board are you using?

August 21, 2010
by egero1
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Just a standard breadboard as far as I know. The other ics are a 4510 and 4511.

dice

August 21, 2010
by mongo
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OK, assumint the notch, (pin1) is toward the left on the 555,I see pins 1 and 2 grounded. (-) Pin 2 should be connected to pin6 but not to the negative rail. Pin 8 looks to be connected to the negative rail but should be to the positive rail.

The 4510 is an up/down counter and the 4511 is a 7 segment bcd decoder/driver. I do not see any connection from the 555 to anything, (pin3)

Not too sure what is connected to pin 5, it should be just a small capacitor to ground.

The picture is a little hard to see.

August 22, 2010
by egero1
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Sorry about the bad pic. I took your advice and I am up and running now. Thank you for your help!

August 22, 2010
by mongo
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Glad it's working. Have fun.

No worries with the pic, it just took a little eye strain to look it over. I think the last one I did was a little fuzzy too.

August 22, 2010
by mongo
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Years ago, I made some similar circuits. I built them on perf board and used them as modules that would plug into the breadboards. I had range selector switches and a potentiometer mounted to the boards so I could adjust the frequencies. Very useful little things.

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