F to V Converter using LM331 Vout 0-5V (better 0-3.3V) Finput 0-1Khz

Other Hardware General Electronics
1

Hello,

I am having trouble doing the calculation for RlCl for this F/V converter circuit.

The supply voltage will be between 11.9 and 15 V (stabilized to 12VDC), the input frequency from 0-1Khz and necessary output voltage for Teensy use will be 0-5V (with R divider) or even better 0-3.3V.

According to the datasheet I have to calculate the resistance of Rl and the capacity of Cl.

The attached image shows the default circuit for 0-10Khz full scale.

Could any help me choosing the right components for 12V supply Voltage, input frequency 0-1Khz and output voltage 0-3.3V (or 0-5V if necessary)?

Thanks!

LM331_FtoV.PNG

lm331-ti.pdf (943 KB)

2

Nobody who could help in this case please?
Thx!

3

So frequency, to analogue voltage, to a digital value.
Isn't it easier (and more accurate) to convert to digital directly.
Leo..

4

the input frequency from 0-1Khz

You can't have that.

The data sheet says:-

Wide Range of Full Scale Frequency: 1 Hz to 100 kHz

5

@Wawa

no, unfortunately not. Even if I use Teensy it is to unstable to count the impulses directly with a refresh interval of 1 second. This due to the huge range. The times will get to big to get an accurate result. If I rember right it was an error abour +- 30% depending on the situation.
Since I need to count to values and subtract them this will not work.

@Grumpy_Mike

The question was something completely different and of course you can if you read the datasheet.
RC and the others resistors declare the range of output voltage and the input range of frequency.

6

The question was something completely different

If you quote your requirements outside the specifications of the chip then that is an error and makes your project impossible.

and of course you can if you read the datasheet.

Grow up, you can’t go down to a frequency of zero Hz.

If you know so much I wonder why you bother asking questions. Oh you don’t do you.

7

autopilotNOR:
no, unfortunately not. Even if I use Teensy it is to unstable to count the impulses directly with a refresh interval of 1 second. This due to the huge range.

BS.

Need to study how frequency couters work.
There are AFAIK two ways.

  1. Count pulses (state changes) for a fixed amount of time.
  2. measure time between state changes (used for very low frequencies).
    Leo..