Good Day,

I want to make a square wave generator with a frequency of 963 Hz, close to 50 percent duty cycle with Voltage greater than or equal to 5 Volts. I already made 555 timer astable multivibrators at lower frequencies from 0.1 Hz to 42 Hz. Now I want to make it at 963 Hz. I have bought a DDS function generator and currently using this to feed it to the load circuit.

But I want to make one circuit separately at this 963 Hz frequency. In other thread I discussed about using MCUs and I was going through the tutorials I found that they can be generated but not below 1 Hz and they use software PWM and hardware PWM for frequency limits with their own limitations. I can use the MCUs to control my analog PWM generators so I am into learning MCUs.

However I like to make this analog 963 Hz PWM square wave generator using the same circuit I used for other lower frequency range using 555 timer, Resistors and Capacitors.

For a 963 Hz 555 Astable multivibrator circuit, I can use the following values.


https://circuitdigest.com/calculators/555-timer-astable-circuit-calculator

However the capacitor value I should use is 10 nano Farad and that is available in ceramic disc type not in electrolytic type.

My question is, can I use this 10 nanofarad ceramic capacitor in this 555 circuit and will it produce the desired output or I should go for other type of square wave generators.

Thanks.

Edit: 693 Hz to 963 Hz in picture

 

Is the frequency 963 or 693 as shown in the calculator?
10nf is OK.
R1 = 2.2K and R2 at 73.8K gets a 963hz at 50.73% duty cycle.
Will need to use a cmos 555 chip to get the output close to the supply voltage. What will be the supply voltage?

 

How accurate do you need the frequency to be? An analogue circuit would be somewhat temperature dependent.

 

Is the frequency 963 or 693 as shown in the calculator?
10nf is OK.
R1 = 2.2K and R2 at 73.8K gets a 963hz at 50.73% duty cycle.
Will need to use a cmos 555 chip to get the output close to the supply voltage. What will be the supply voltage?

Its 963, I have edited it in the main post. 10 nF I like to know if its ok to use ceramic capacitors instead of electrolytic capacitors. Because ceramic capacitors are available at that value of 10 nF and electrolytic is not available. Supply Voltage is 5 Volts but output can be between 4 to 5 Volts.

 

I like to know if its ok to use ceramic capacitors instead of electrolytic capacitors.

Yes. Ceramic capacitors have a longer life than electrolytics and a closer tolerance.

 

How accurate do you need the frequency to be? An analogue circuit would be somewhat temperature dependent.

I like it to be accurate as possible depending upon the feasibility. I am using lower frequency analog generators and they seem to work fine in my application so that shouldn't be a problem.

 

Yes. Ceramic capacitors have a longer life than electrolytics and a closer tolerance.

Ok so I can use this type of ceramic Capacitor for 10 nanoFarad.

Thanks I had a doubt if I could use it for this square wave generator. If this can be used there shouldn't be a problem.

 

The big question is always about accuracy and stability. If you just need "about 963 Hz, an analog circuit with stable components should possibly work.
BUT if you need 963.00Hz all the time then it gets possibly a bit more complex, especially if you also need that 50.00% duty cycle. At that level you need a crystal oscillator with a divider string. But entirely possible with a custom preset crystal oscillator, which at the time I procured it from Digikey for less than $10 USD.

 

74HC4060 with a 15.81MHz crystal will give you 965Hz. Is that near enough? And after fourteen divide-by-two stages, you can be pretty certain that the mark-space ratio is 50%.
One IC, One crystal, one resistor and two capacitors.

 

74HC4060 with a 15.81MHz crystal will give you 965Hz. Is that near enough? And after fourteen divide-by-two stages, you can be pretty certain that the mark-space ratio is 50%.
One IC, One crystal, one resistor and two capacitors.

Thanks but if its much closer using the 555 circuit then that would be a better option.

 

The big question is always about accuracy and stability. If you just need "about 963 Hz, an analog circuit with stable components should possibly work.

Thanks. I hope it does.

 

Crystal and divider circuit is spot on. Using the 555 I'd recommend adding a trimmer pot to adjust to the exact freq. And even then, the freq is temp dependent where the freq divider circuit isn't.

 

You need to state the accuracy required. 963Hz ±?Hz or ±?%
555-timer circuit is sensitive to temperature drift.
You can do it with an MCU and you can produce 50% duty cycle.
There is no lower limit to the generated frequency. Yes, it can output 0.00000001 Hz if required.

 

You need to state the accuracy required. 963Hz ±?Hz or ±?%
555-timer circuit is sensitive to temperature drift.
You can do it with an MCU and you can produce 50% duty cycle.
There is no lower limit to the generated frequency. Yes, it can output 0.00000001 Hz if required.

I have been searching on google and on youtube tutorials I couldnt find PWM generation using Pi Pico or Arduino at lower frequencies. Let me know the MCU and if you can possibly give a link to that tutorial or an explanation to how its done using the MCU.

Thanks.

 

Thanks but if its much closer using the 555 circuit then that would be a better option.

965Hz is a 0.2% error. You won' t get better than ±12% with a 555, because that is the error on the trigger and threshold levels, so it is sixty times better.

 

965Hz is a 0.2% error. You won' t get better than ±12% with a 555, because that is the error on the trigger and threshold levels, so it is sixty times better.

Ok I didn't know that. Thanks for the information.

 

Yes. Ceramic capacitors have a longer life than electrolytics and a closer tolerance.

Depends on what you buy. Electrolytics can be had in 3% at best and most hobby markets are more in the 10-20% range or sometimes better. Ceramics in the hobby market are usually in the 20% range and if buying "kits" from china that maybe more like 100% tolerance or worse. I have some hobby markets that are pretty close to spot on and overall, less than 10%. But, ceramics don't dry out and short and come in lower values than electrolytics... Then there is mylar,polyester, mica...

 

Then there is mylar,polyester, mica...

I can get polyester capacitor of 10 nF value.

 

965Hz is a 0.2% error.

I can get 16 MHz Oscillator in my place not 15.81.

 

Just about any MCU with a timer/counter module can do it.
If the timer/counter module is clocked at 1 MHz, you toggle a GPIO pin every 519 clock pulses.
This gives a period of 1038 μs which is 963.39 Hz.