Down convert Frequency to a readable value

[MikeMl]

The 1N749 is a 4.3V Zener. The 0.7V forward drop of a Si diode adds to the Zener voltage to create a Vdd of ~5V. The 12V input signal is clamped to ~5V to prevent latch-up of the CMOS chip.

 

[stuhagen]

The 1N749 is a 4.3V Zener. The 0.7V forward drop of a Si diode adds to the Zener voltage to create a Vdd of ~5V. The 12V input signal is clamped to ~5V to prevent latch-up of the CMOS chip.

They are real close

 

[MikeMl]

1N5229 should work better than the one I showed... It likely has a sharper knee, and better regulation.

 

[stuhagen]

Hmmm, I wonder if this design could incorporate a pot or something to be able to "tune" inbetween the divders. Like 2.5x, etc.

 

[dougy83]

Hmmm, I wonder if this design could incorporate a pot or something to be able to "tune" inbetween the divders. Like 2.5x, etc.

It's a digital integer divider. Being digital, RC filters and pots are not going to adjust its division ratio. If you want to divide by fractions, there are ways to do it, but not by connecting a pot to a 4017.

You can have a look at PLLs, which can multiply the input frequency, which you can then divide to get some fractional output frequency.

 

[Mr RB]

Hmmm, I wonder if this design could incorporate a pot or something to be able to "tune" inbetween the divders. Like 2.5x, etc.

There are plenty of vehicle speedo and tacho recalibrators on the market, that allow you to "tune" the frequency conversion ratio to a fine degree. Prices vary from about $70 to $100, for a pro unit with all the necessary automotive voltage protection etc.

 

[stuhagen]

Well darn... I bread boarded it up tonight and it isnt working well. The only functioning part is the divided X2 on Pin 4 and that's all. I input 400hz and it is a smooth 200hz out. Every other pin the signal jumps all around and not flat and stable. Not sure where to go to isolate the issue. I may tomorrow start over just in case I made a bad connection. But I triple checked it.

 

[dougy83]

Just use pin 3 for the frequency output signal always. Ignore the outputs on all other pins.

Connect pin 15 to an appropriate "decoded output" pin to set the divide ratio. e.g. pin 15 to pin 4 to get a divide by 2 at pin 3.

 

[stuhagen]

OK my mistake....it works fine. I had the Vss to pin 8 ground not attached. Whereas I had ALL the components attached to Pin 8, just not the ground. Jeesh. I also had to use my other Freq Generator as the one I was using max's out at 400hz. Now to get some boards made!