NerdKits - electronics education for a digital generation

You are not logged in. [log in]

NEW: Learning electronics? Ask your questions on the new Electronics Questions & Answers site hosted by CircuitLab.

Basic Electronics » 555 astable on breadboard

August 21, 2010
by egero1
egero1's Avatar

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
mongo's Avatar

What frequency are you looking at operating?

August 21, 2010
by egero1
egero1's Avatar

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
egero1's Avatar

R2 is 47k ohms, not 4k ohms. That was a typo.

August 21, 2010
by mongo
mongo's Avatar

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
egero1's Avatar

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
mongo's Avatar

Shat kind of bread board are you using?

August 21, 2010
by egero1
egero1's Avatar

Just a standard breadboard as far as I know. The other ics are a 4510 and 4511.

dice

August 21, 2010
by mongo
mongo's Avatar

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
egero1's Avatar

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
mongo's Avatar

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
mongo's Avatar

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.

Post a Reply

Please log in to post a reply.

Did you know that you can build an analog amplifier with one transistor and a few resistors? Learn more...