Convert pulse frequency to DC volt??

S

settra

Member

• Feb 4, 2014

• #1

hey forum. i have a hall effect sensor, measuring the RPM of a wheel, with one magnet attached to the wheel. every time the wheel magnet passes from the sensor, it goes low.... so, one pulse per revolution...

i want to convert that signal, to analogue... 0 rpm = 0volt, more rpm = more volt (max 5v)... any ideas how can this work??
i have found LM2907 , which is an Frequency to volt converter, but it is supposed to work with VR sensors (who outpout -V as well). do you think it would work with a hall effect sensor switched to ground??

what else could work?? thanks!

 

ericgibbs

Well-Known Member

Most Helpful Member

• Feb 4, 2014

• #2

hi settra,
The LM2907 should work OK, do you have a datasheet to post for your Hall effect sensor.?
E

 

S

settra

Member

• Feb 4, 2014

• #3

I Don't really have any info on the hall sensor... :/ but its the plain simple style. i had asked "give me one hall effect sensor" , and took what the shop gave me , so... is it for something important?
as i remember, the Vcc and signal, are tight together with a 10k pull up resistor!

 

ericgibbs

Well-Known Member

Most Helpful Member

• Feb 4, 2014

• #4

If the Hall effect works with a 5V supply and its output swings from approx 0V to ~5V, it should not be a problem driving the Lm2907

 

S

settra

Member

• Feb 4, 2014

• #5

its something like that for sure. BUT , the otpout is 5v, and swings to 0v ... (so its 5v most of the time )

 

S

settra

Member

• Feb 4, 2014

• #6

any other way i could do that?? becouse it might not be easy for me to find a LM2907 where i leave... :/

 

ericgibbs

Well-Known Member

Most Helpful Member

• Feb 4, 2014

• #7

settra said:

any other way i could do that?? becouse it might not be easy for me to find a LM2907 where i leave... :/

Click to expand...

Whats is the highest RPM you need to measure.?

 

dr pepper

Well-Known Member

Most Helpful Member

• Feb 4, 2014

• #8

You can use a 555 as a frequency meter, do a google.

 

S

settra

Member

• Feb 4, 2014

• #9

enothet thing, is that i want outpout 0-5 v... i think that LM needs 12v min....
highest rpm? i dont think more than 1000rpm, considering that the typical car wheel is 16" diameter...

 

S

settra

Member

• Feb 4, 2014

• #10

after all, i managed to find, lm2907 with 16pins, and Lm2917 with8 pins.... do you think that the wire up should be the same???

 

ericgibbs

Well-Known Member

Most Helpful Member

• Feb 4, 2014

• #11

settra said:

after all, i managed to find, lm2907 with 16pins, and Lm2917 with8 pins.... do you think that the wire up should be the same???

Click to expand...

The datasheet for the LM2917 shows similar circuit examples as the LM2907.
So either type should be OK.

Have you considered the 555 option.?

 

ericgibbs

Well-Known Member

Most Helpful Member

• Feb 4, 2014

• #12

hi,
This is a rough idea of the Vout you will get, the actual Vout will depend upon your components.
E

 

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S

settra

Member

• Feb 4, 2014

• #13

i cant seem to be able to get it to work.... i could see the lm555 as well, but i dont seem to be able to find a a good circuit describing how... :/

 

ericgibbs

Well-Known Member

Most Helpful Member

• Feb 4, 2014

• #14

settra said:

i cant seem to be able to get it to work.... i could see the lm555 as well, but i dont seem to be able to find a a good circuit describing how... :/

Click to expand...

Please post your circuit and if possible a photo on how its connected, it should work.

 

S

settra

Member

• Feb 4, 2014

• #15

its like the one you posted, but :

i give direct dc to pin one, with a pushbutton (although i tried with a 22pf cap)
c1 = 2.2uF
R1= 100k
and i also have no C2, but i think that this is for ripple only....
maybe i have arledy burned it ?
where did you made the simulation ?

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• Feb 4, 2014

• #16

settra said:

i cant seem to be able to get it to work.... i could see the lm555 as well, but i dont seem to be able to find a a good circuit describing how... :/

Click to expand...

There's masses of 555 examples, here's one:

https://www.555-timer-circuits.com/car-tachometer.html

 

dr pepper

Well-Known Member

Most Helpful Member

• Feb 4, 2014

• #17

Another, this one has some amplification on the front end:

**broken link removed**

 

S

settra

Member

• Feb 5, 2014

• #18

cool. thanks allot for the help guys!! i will see what i will manage to succed

 

U

usman88

New Member

• Nov 18, 2014

• #19

hai settra....
i have problem like you, i want to convert sensor hall effect with pulse widht to voltage.
i have IC LM2917 (14 PIN), but not succes to convert voltage 0-5 VOLT, i want to try use IC 555.
if you succesfully with your circuits, please post the circuits.

thanks

 

OlPhart

Member

• Nov 20, 2014

• #20

Howdy, I built speed & tach measurements for a motorcycle instrument complex by timing the span between pulses.
It's then a straightforward calculation to MPH or RPM. The other numbers are time constants or stuff like tire diameter.
This is predicated on using a microcontroller, so may be somewhat advanced. I wasn't born knowing it either... G.H. <<<)))