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.
I am looking for a simple square wave circuit with for instance a Nand chip and a 32kHz quartz plus a few components to get a signal with at least 4 V peak to peak .
I've seen a few circuits for higher frequency crystal .
Does someone have a scheme ?
Thanks for your help .
Have you an idea about the way to choose the resistor and capacitors .
Up to now, as I didn't have a CD4011 , I've tried to do the circuit with a
The capacitors I use are 100 pF and I've tried several resistor values from 1MOhm to 10MOhm without getting any oscillations .
Is there another way to get these values than trying every (R,C) possible couple ?
There may be a few ones
The crystal is ok as it oscillates nice with the prebuilt oscillator circuit inside the pic16F84 or pic16F628 .
The problem is that I'd like to use just one pin for the clock, that's why I need to do an external 32kHz clock .
I also had the idea that a CMOS inverter would be better.
As I only had 74HCT04 by hand at home, that's why I used it for my experiments .
I'll try to get a 74HC04 , that might be the clue with the circuits on the sci.electronics
link that Ken proposed. That's what I was looking for
Thanks guys for your help
Because of the price, the pic 16F676 is one of the cheapest but only has 12 I/O pins .
Anyway, I've seen some pic16F887 with a really good price , and switching to it would solve these problems .
In the closest electronics shop from my home , there's more or less 7 dollars difference, between 16F676 and the bigger pics, whereas a single 74HC04 costs 0,30 $ .
I am doing this clock as a project for a kid , thus it has to be cheap , a kind of introduction to micro-controllers and programmation .
I've been trying to make a 32.768 kHz oscillator following this **broken link removed** .
It does oscillate, but the frequency is always slightly higher than 32768 Hertz .
I've tried several values 22 , 27, 33, 39, 47 pF without the frequency getting closer to 32768 than 32776 Hertz .
In order to tune I have put an adjustable capacitor of different values without success .
Is there a way to slow down a little bit the oscillator ?
Ok, I'll try both of your advices .
In the scheme, the second capacitor is defined as 39 pF adjustable,
What do you think that means :
** ) is it an adjustable which max value is 39 pF
** ) or else the most likely correct value should be 39 pF , thus 39 pF should be within the range of the adjustable capacitor and not the upper limit of its capacitance .
I thought my problems were done, but actually, I still have a problem.
The output of the 32768 kHz oscillator is fine, it goes from 0V to 5V, the edges are sharp . I would have liked to divide the frequency using a 74HCT4060 counter .
The input signal is fine on pin n° 11, pin 12 (MCLR) is tied to ground and I've put a 330nF capacitor between the power supply and ground, and the signal on the output is anything but a 32768 kHZ divided clock.
I can't get any stable view of it, even using the scope with level-triggered sweep , it's not periodic .
What is strange is that I've already changed the first 4060 and I get
exactly the same results with the second one .
If anyone has an idea about what's going wrong , thanks for your help