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Topic: LM2917 Frequency to Voltage Converter (Read 20415 times) previous topic - next topic

Saabman

I realise this is an old topic but it doesn't seem to have a solution.

Just in looking at the data sheet for the LM2917 i noticed it has an internal zenner diode connected to pin 6. Your circuit depicts pin 6 connected directly to 9V rather than is suggested in the data sheet of using a 470ohm current limiting resistor between pin 6 and the power supply.

It is possible that the internal zenner is sinking the excess current and thus producing the unwanted heat.

Bernie

Pelleplutt

I'm always think out of the box. Why have an digital signal make it to an analog signal and then make it digital again.
Use the tacosignal directly and measure the time between two pulses. RPM are the inverse  funktion of time.
Perhaps you need a prescaler I don't know how fast signals the arduino can measure .

Saabman, du råkar inte vara från Sverige?

Pelle

donperry

Old thread but since I'm currently exploring doing the same, wouldn't a mosfet triggered by the signal wire that outputs 5V into the arduino...then count the rate of that pin turning on and off using micros... then some calcuations. Wouldn't that be easier?

sindagi2

Old thread but since I'm currently exploring doing the same, wouldn't a mosfet triggered by the signal wire that outputs 5V into the arduino...then count the rate of that pin turning on and off using micros... then some calcuations. Wouldn't that be easier?
That really depends on the arduino/micro you're using. If you have one with high enough clock speeds and low enough input frequency, that would be an easy way to do it. I'm using these chips right now for an anti-skid/traction control application where I need to take an input from 4 wheels, average the fronts and backs, measure the difference and act on it.
An arduino might not work here because I have 4 inputs. The frequencies are high enough that I'd need to use interrupts and it's almost entirely possible that the arduino gets interrupted while handling another interrupt, causing unpredictable timing behaviour.
On the flip side, using an ic like this, would let me implement my whole circuit with analog components and no microcontroller at all

ted

you don't need converter, you need arduino frequency meter and convert it to RPM

raschemmel

Can you attach the schematic of the circuit using the "Attachments" button in the lower left corner of the screen ?
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

allanhurst

I can't see your circuit.

Have you used a current limiting resistor ( datasheet suggests 470R) in series with the supply?

Allan

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