LM2917-N: Hall Effect Vehicle Speed Sensor

Dul Joni

Part Number: LM2917-N
Other Parts Discussed in Thread: NE555, LM231

Hi ....
Please forgive my bad language,
I'm from Indonesia and still studying in electronics

I plan to make a Vehicle Speed Limiter for Common-rail Truck with LM2917N-14. The input signal comes from Speed Sensor (Hall Effect Element) with pulse output 15Hz-600Hz, 2V-6VDC.
I read on Google for the Sine Wave input LM2917, it can be directly connect while the Hall Effect must be driven by the Transistor first, it's that true?, because I tried the input from NE555 Variable Square Wave Signal generator and XR2206 cheapest function Generator LM2917 can be work well (DC output proportional with the input frequency both Sine and Square Wave Signal).

I use a standard circuit from the datasheet. At input LM2917 (pin 1), is that need a filter circuit or RC Network? If so, how to configure it and values (I need advise)

Is the value of pin-2 capacitor (10nF) sufficient/appropriate? and Does the pin 3-4 Capacitor must polarity (electrolyte or tantalum)? currently I am using a non-polar Multilayer Ceramic Capacitor

I really hope the answers, Thank you .....

over 5 years ago

0 Raymond Zhang1 over 5 years ago

TI__Guru* 77221 points

Hi Dul,

I plan to make a Vehicle Speed Limiter for Common-rail Truck with LM2917N-14. The input signal comes from Speed Sensor (Hall Effect Element) with pulse output 15Hz-600Hz, 2V-6VDC.

From 15hz-600Hz is proportional to Vout = 2 to 6V, this will generate (600-15)Hz/4V = 146.25 Hz/V.

I am able to get approx. 100 Hz/V for F2V conversion, and has a little trouble to get the above requirements. Is 146.25Hz/V a fixed requirements?

Enclosed are two simulations and an application note that you may be interested in. Please let me know if the requirements are flexible.

/cfs-file/__key/communityserver-discussions-components-files/14/LM2907_5F00_F2V-08142020.TSC

/cfs-file/__key/communityserver-discussions-components-files/14/LM2917_2D00_14-E2E-08142020.TSC

https://www.ti.com/lit/an/snaa088/snaa088.pdf?ts=1597465612014&ref_url=https%253A%252F%252Fwww.google.com%252F

Also, take a look at LM231 part below.

https://www.ti.com/lit/ds/symlink/lm331.pdf?ts=1597466203487&ref_url=https%253A%252F%252Fwww.ti.com%252Fsitesearch%252Fdocs%252Funiversalsearch.tsp%253FsearchTerm%253Dfrequency%2Bto%2Bvoltage%2Bconverter

Best,

Raymond

0 Dul Joni over 5 years ago in reply to Raymond Zhang1

Prodigy 30 points

Hi Raymond ..... thanks for your reply

F2V value does not must to be accurate, 15hz(2V) to 600Hz(6V) is only the result of measurements from field technicians using a DMM. So, 100Hz/V is very acceptable, because the LM2917 for Speed Limiter which is only active at certain speeds, for example 60Km/Hr (approximately 250Hz) or 80Km/Hr (approximately 300Hz). Therefore, I use Trimmmer Pot at pin3 so that it can be adjusted to the condition of the car/field.

My question is can the sensor directly connect with the LM2917? or must use Transistor first? and is that need a filter circuit or RC Network? If so, how to configure it and values (I need advise)

0 Raymond Zhang1 over 5 years ago in reply to Dul Joni

TI__Guru* 77221 points

Hi Dul,

My question is can the sensor directly connect with the LM2917? or must use Transistor first? and is that need a filter circuit or RC Network? If so, how to configure it and values (I need advise)

The image below is the input common-mode voltage requirements. If the input Tach sensor meets the requirements, then it can be connected directly.

LM2917 depends on 8 or 14 pin package. For 8 pin package, Tach- has to be connected to ground, see red box above. For 14 pin package, you can configure your own Tach- at pin 11.

I have sent you the simulation, you may simulate it via Tina. If you need further assistant, please let us know.

Best,

Raymond

0 Dul Joni over 5 years ago in reply to Raymond Zhang1

Prodigy 30 points

Yes, I've seen the simulation on Tina and it's really helpful.

From the data above, whatever the waveform (sine or square wave) the Tacho sensor can be directly connected to the LM2917N without need a transistor because it meets the requirements.

Thank you Raymond your explanation is very helpful
May God bless you ......

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LM2917-N: Hall Effect Vehicle Speed Sensor