Crystal for Inverter 3.2768MHz Unavialable

Hai,:roll:
I have modified an inverter circuit for soldering iron published in Electronics For You . I added 50hz frequency generator from another circuit published in Electronics Projects handbook.

I I suffering from the unavailability of Crystal of frequency 3.2768 Mhz :-?, Can i substitute it with 32.768 KC??
Its modified schematic is added

Output is taken across 10Uuf capasitor

You have a crystal of 3276800 Hz , you are using CD4060 to divide this by a factor of 16386 (2^14) and then divide two more times using CD4013 for a total factor of 65536 (2^16).
3276800 / 65536 = 50 Hz

If you use a 32768 Hz crystal you will get 32668 / 65536 = 0.5 Hz
If you want you can take the output from Q9 without using the CD4013 stages for a factor of 512 (2^9) , you 'll get 64 Hz , if it suits you.
32768 / 512 = 64Hz
I think the oscillator values need to change too.

Alex

You might lose some efficiency if you move from 50Hz to 64Hz and anything with a motor inside it may run at the wrong speed. You should be able to find a crystal at 3.2768MHz though, it is a very commonly used frequency.
There is an error in your schematic, the center tap of the transformer should go to +12V not to ground!

Brian.

I see, that 3.2768 MHz crystals are available a most catalog distributors and qualified DIY electronics shops. May be different in your country, unfortunately.

The best way is to find a crystal with a frequency, that's an integer multiply of 100 Hz. (You need a final 2:1 DFF for 50% duty cycle). 1 MHz or 4 MHz would be a common value. Then you can build a frequency divider with respective ratio by any circuit of your choice, e.g. decade counter ICs, binary counters with programmable preset, binary counters with external feedback logic.

A CD 4060 or 4040 can be e.g. set to an integer divider ratio by a diode/resistor feedback network. But it works only at low frequencies due to the finite progation time of the ripple counter. Synchronous binary counters are better suited to set up arbitrary divider ratios.

If you don't need exact 50 Hz, but would be satisfied with e.g. 49.95 Hz, even a 32.768 kHz watch crystal with a 328:1 divider can do.

P.S.:

There is an error in your schematic.

Click to expand...

There are more. The circuit claims to drive the 2N3055 transistors through a 10 Ohm 5W resistor from a CD4013. Sounds like a bad joke. Refer to some of the uncountable inverter circuits at edaboard, how they drive the output stage.

FvM said:

Ithrough a 10 Ohm 5W resistor from a CD4013.

Click to expand...

The actual value is 10E 0.5 watt where he has inserted a decimal for one and has omited for other and the value looks odd.

Regarding your confusion and difficulty to get the crystal, i would like to ask you first, the original circuit must have been designed with a 555 or a Cd 4027 as an oscillator as i remember which is variable, and was working fine as i have worked with similar circuit from EFY. Why you need a crystal controlled one despite these problems?

as i have worked with similar circuit from EFY

Click to expand...

I guess, it doesn't drive a 5A 2N3055 push-pull stage from a CD4xxx CMOS gate without additional current gain?

betwixt said:

You might lose some efficiency if you move from 50Hz to 64Hz and anything with a motor inside it may run at the wrong speed. You should be able to find a crystal at 3.2768MHz though, it is a very commonly used frequency.
There is an error in your schematic, the center tap of the transformer should go to +12V not to ground!

Brian.

Click to expand...

:wink:Yes the center taped goes to ground Sorry I make a mistake while drawing .