1 Hz square wave generatorusing 555

No ;-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

Do you mean a clock to keep time? If so, the 555 will be nowhere near stable enough.

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If your clock is a kitchen timer intended to be used for hard boiled eggs only, yes.

At that frequency they're likely going end up pretty damn soft-boiled.

Best regards, Spehro Pefhany

Posting a basic question like this in sci.electronics.basics would get you more respect. I don't have the timing formula for the 555 in astable in front of me but I think you're actually getting about 100 Hz with those values. Either change the cap to 100 uF, or keep the cap and multiply each resistor by 100. Then hook up a led or tiny light bulb so you can visually check the output of the 555 and count it off against a clock or stopwatch. And as others have pointed out, an RC oscillator like the 555 wouldn't make a stable, accurate clock for any application demanding more accuracy than timing eggs.

It looks like you need a 100 uF cap? I dunno, I suck at teh maths. There are bunches of javascript 555 calculators out there, google around for one. If you are in fact using this as a time-of-day clock, as you may have gathered from other replies, you will have to deal with drift, but if you're tricky you can still get it to work. If you really want accuracy, you might be better off dividing a crystal oscillator or deriving your clock from the AC power.

If you really really want to use a 555, ZiLOG makes a 555 replacement IC that's all crystal- and microcontroller-based, and will keep accurate time in a clock.

Use a CD4060 and a 32768Hz crystal and you'll get closer. If you add one more flip-flop, you'd get very close. I suggest a second CD4060 and the observation that 7+8=15.

a good frequency counter 1Hz - 50 MHz is in

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