Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Output 'on' (high) to 'off' (low) ratio. 50% duty cycle would be equal high and low time per cycle. 90% duty cycle would be output high most of the cycle.
Here is a sinewave output from a 555: **broken link removed**
The output has "high impedance" and needs buffering. In other words, the output waveform is "very delicate" and will change shape if it is loaded or passed to a stage that has a low resistance.
You will have to choose values for R and C (on the output) to get the waveshape you require. It is not a perfect sinewave but is called "an approximation."
Depends on if you actually need a real sinewave or not antknee, colins circuit will give you a filtered square wave output, I'd hardly consider it a sinewave, it'll jut be a bit more gentle than a square wave, it'll still contain plenty of harmonics.
I don't need an exact sine wave. I will have a look to see if the harmonics are going to be an issue. Cheers. Am going to put it together now at 100KHz.
One way to get a nice sine wave out of a 555 is to filter the (square wave) output with an LC filter rather than an RC filter. If the frequency is not too low a small inductor will do the job. The LC filter should follow the resonate frequency formula for L and C:
F=1/(2*pi*sqrt(L*C))
In other words, if the output is 10kHz then L and C must be such that in the above formula F=10kHz also.
Of course this is best when you only need one sine wave frequency output, as C will have to change for somewhat different frequencies.
That is excellent thank you. I just tried it with two 10uF caps and 3.3K resistor because those are closest to hand. The square wave has rounded off a little, it is hard to tell if I'm getting minus volts, I presume so, but I have difficulty working out how to ground my scope so it is hard to tell!
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.