0.5 - 3Hz generator

[willtucker]

I need a circuit that gives out 0.5Hz to 3Hz. It is for a metronome project. I have tried 555s but i would like to try another method. Simplicity is vital. If the 555 is the best method just say although it does have a margin of error. It would help if it was a 50% duty cycle or there abouts but definatly no more then 50%.

Cheers

Will

 

[Roff]

Seems to me like a 50% duty cycle will give you 2 clicks per cycle. Don't you want just one per cycle, as you would get with a low duty cycle pulse?

Edit:
I am not a musician. I looked at a schematic (perhaps one you have built) and discovered that it generates a gated 1600Hz tone, with the tone being on some percentage of the time at the beat rate. Hmmm....

 

[Optikon]

I need a circuit that gives out 0.5Hz to 3Hz. It is for a metronome project. I have tried 555s but i would like to try another method. Simplicity is vital. If the 555 is the best method just say although it does have a margin of error. It would help if it was a 50% duty cycle or there abouts but definatly no more then 50%.

Cheers

Will

well, the 555 generally speaking isnt very good at too high or too low frequencies. But I think its possible to do reasonably well.

You could consider using a 32.767kHz watch crystal oscillator (check for 50% Duty) and a 13 bit counter for a divide by 8192. That will give you a nice stable 50% 4 Hz clock for which you can use another 8 bit counter to further divide this down in a stable fashion. Then you can pick off a nice discrete set of < 4Hz frequencies with switches to use as you wish. Counter logic chips & crystals are cheap.

 

[chemelec]

I find that the 555 is Quite Stable, If you use Good Quality Caps and Resistors.

But I will agree a Xtal osc is Better, but Far more Expensive.

 

[mechie]

Metronome mark space ratio

I would have thought that the 555 timer would be in its element at these sorts of frequencies?

I agree with RonH ...
I don't understand why you want a 50/50 mark-space ratio, I think this is just adding to the difficulty of the design. Either make it as narrow a pulse as possible (audibly just a 'click') and have one pulse per music beat, either that or use a series capacitor followed by a diode to ground so that only positive-going edges come through to be heard at the output?

RonH The gated tone is just a nice way of making the audible 'click', imagine a drummer tapping a nice steady beat- I think a narrow pulse to a speaker cone could sound similar ?.

Optikon Whilst the divider idea would give brilliant stability I would think it needs to be adjusted in steps much smaller than 1/4 second (equivalent to 15 beats per minute) to be truly useful in music - your idea could be adapted to 1/60 second increments to allow setting to the nearest integer beat per minute ?

 

[Optikon]

Re: Metronome mark space ratio

I would have thought that the 555 timer would be in its element at these sorts of frequencies?

I agree with RonH ...
I don't understand why you want a 50/50 mark-space ratio, I think this is just adding to the difficulty of the design. Either make it as narrow a pulse as possible (audibly just a 'click') and have one pulse per music beat, either that or use a series capacitor followed by a diode to ground so that only positive-going edges come through to be heard at the output?

RonH The gated tone is just a nice way of making the audible 'click', imagine a drummer tapping a nice steady beat- I think a narrow pulse to a speaker cone could sound similar ?.

Optikon Whilst the divider idea would give brilliant stability I would think it needs to be adjusted in steps much smaller than 1/4 second (equivalent to 15 beats per minute) to be truly useful in music - your idea could be adapted to 1/60 second increments to allow setting to the nearest integer beat per minute ?

Yes more dividing (1/6) would be useful.. I'm sure there is a less parts way.. but it isnt really clear why the author seemed to dislike 555 circuit..??
Isn't a metronome just a "click click click" at regular intervals for timing?
So really just a variable pulse generator and 50% duty seems unimportant to me as long as the timing is what you need. I thought it was begging for a 555 solution but like I said, why does the author not like it?

 

[audioguru]

I don't think that you need crystal accuracy for a metronome. Besides its frequency can't be smoothly adjusted. An ordinary varyable-frequency oscillator with a short pulse should be OK. It might need a regulated supply for frequency stability.

Why does the author dislike 555s? They eat a fair amount of current so a 9V battery won't last long. They are designed for a 200mA pull-up or pull-down load, so they create a 400mA supply spike when switching.
A CMOS 555 doesn't have these problems and its 100mA output can drive a small speaker through a resistor. Its resistors can be mismatched to create a short pulse each cycle.

The speaker can be placed in or near a tube or chamber so the resonance mimics a wooden mechanical metronome.