What DAQ? device can I use to read a Gear-Tooth Speed sensor?

Thread Starter

Kulanib

Joined Jul 6, 2022
55
Has anyone mentioned the LM2917?
Directly interfaces to variable reluctance sensors, easily interfaces to other sensors, and gives a voltage output proportional to frequency.
Yes, @Irving Has mentioned the chip in the examples he linked.

This chip with its simple company’s would be ideal indeed. My sensor is an NPN type which is 4.5-24 V (supply and output with a pull resistor) and outputs a digital 4.5-24 V (square wave). It would be awesome to connect this sensor to the IC.
 

Ya’akov

Joined Jan 27, 2019
9,264
Has anyone mentioned the LM2917?
Directly interfaces to variable reluctance sensors, easily interfaces to other sensors, and gives a voltage output proportional to frequency.
Talk about a solution on a chip, there’s an example. Not only is it everything you need in hardware to do a tachometer it can be a touch switch or a capacitance meter.

Here’s one time when even a little 8-pin MCU is defeated as best choice (for its λ → V function at least).

I wasn’t aware of this chip, thanks for pointing it out, goes into the library
 

Thread Starter

Kulanib

Joined Jul 6, 2022
55
Okay, I am going for the LM2917 (data sheet link)

Please Help me with the sizing of my components. I would like to read up to 2 kHz input frequency. My sensor is configured to 5V Hall effect NPN (Vcc, Ground, Output pins - sinks it’s current to ground - pulls up output to Vcc, currently 5 V).

My DAQ (USB 6002) devices Analog is up to 10 V with 16-bit resolution.

For the life of me, I can’t locate C1 and R1 will on the diagram


D235F63F-EC29-4A37-8AB9-D95D2C9DF1D0.jpeg
 

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Ian0

Joined Aug 7, 2020
10,244
Talk about a solution on a chip, there’s an example. Not only is it everything you need in hardware to do a tachometer it can be a touch switch or a capacitance meter.

Here’s one time when even a little 8-pin MCU is defeated as best choice (for its λ → V function at least).

I wasn’t aware of this chip, thanks for pointing it out, goes into the library
Several decades ago I used it to rebuild the innards of Smiths tachometers for classic cars. The input can be connected to a piece of insulated wire taped to the HT lead.
It's old enough to have a data sheet which shows the internal circuitry, and it looks like it is a close relative of LM393 and LM358; and maybe even 555.
 

Ian0

Joined Aug 7, 2020
10,244
Okay, I am going for the LM2917 (data sheet link)

Please Help me with the sizing of my components. I would like to read up to 2 kHz input frequency. My sensor is configured to 5V Hall effect NPN (Vcc, Ground, Output pins - sinks it’s current to ground - pulls up output to Vcc, currently 5 V).

My DAQ (USB 6002) devices Analog is up to 10 V with 16-bit resolution.

For the life of me, I can’t locate C1 and R1 will on the diagram


View attachment 270993
For C1 R1 and C2 see figure 13.
For your sensor, get the 14-pin variety of LM2917, and bias the unused input to about 2.5V (equal values resistors to 5V and 0V)
 

Thread Starter

Kulanib

Joined Jul 6, 2022
55
For C1 R1 and C2 see figure 13.
For your sensor, get the 14-pin variety of LM2917, and bias the unused input to about 2.5V (equal values resistors to 5V and 0V)

Okay, so I got my hand on the 14 pin version.

please for the love of electronics drawn me up a connections and components circuit for this 14 pin LM2917 for my sensor.It would just simplify Everything, the I will be clear.
NB, I want to read up to 2kHz.
 

Thread Starter

Kulanib

Joined Jul 6, 2022
55
For 10v out at 2000Hz and Vcc=15v, then R1=27k 1% + 10k multiturn trimmer, C1=10nF 5% polypropylene

Something like (but check it):

View attachment 271005
Did I accidentally walk into the doors of an Electronic haven??

This is just awesome and you are all awesome.

Thank you so much, you are awesome. You are all awesome, and as you can see, I am wasting no time.

4B97734B-F4B6-4CF7-AFDE-F97C69D27B4D.jpeg4B97734B-F4B6-4CF7-AFDE-F97C69D27B4D.jpeg
 

Ian0

Joined Aug 7, 2020
10,244
Could be a haven - somewhere peaceful and serene - away from all the problems of electronics not working and blowing up.
 

Irving

Joined Jan 30, 2016
4,047
Glad to help.

Some other notes:
1. the output is ratiometric to the Vcc supply so for best accuracy/repeatability the 15v needs to be stable; the actual value isn't critical, its stability is.
2. temperature will affect the values of C1 and R1 so ensure the circuit is away from sources of heat and in a stable environment.
3. VR1 allows calibration against a known 2000Hz pulse from a signal generator. It should cater for tolerances of 1% on R1, 2% on C1 and 2.5% on Vcc.
 

Thread Starter

Kulanib

Joined Jul 6, 2022
55
Revised component values:

C1 = 4n7 5%
R1 = 68k 1%

will give better linearity and more top end clearance...
@Irving Thanks again. Are you available for a chat on discord quickly? Just to minimize the messages, coz I have some specific questions. If so, here's a discord link.

Thank you.
 
Last edited:

Irving

Joined Jan 30, 2016
4,047
Sorry I've never used discord.

AAC policy is to keep discussions here to better disseminate knowledge, so fire away...
 

Thread Starter

Kulanib

Joined Jul 6, 2022
55
Sorry I've never used discord.

AAC policy is to keep discussions here to better disseminate knowledge, so fire away...
Understood.

What simulation/design software can I use to test the parameters of the circuit before spec'ing it?
 

Thread Starter

Kulanib

Joined Jul 6, 2022
55
For 10v out at 2000Hz and Vcc=15v, then R1=27k 1% + 10k multiturn trimmer, C1=10nF 5% polypropylene

Something like (but check it):

View attachment 271005
And I have also noticed that you translated the 8-pin variant of the LM2917 to the 14-Pin variant used in the diagram - how did you know which pin corresponds to which one?

The datasheet does not discretely indicate the function/name of each pin - just a number (some pins do have descriptions like Vcc and frequency in). Or maybe I can't read datasheets.
 

Irving

Joined Jan 30, 2016
4,047
Its all in the full data-sheet:

1657295554439.png1657295598852.png

All the important connections are there and the details of the differences are listed in various sections later on. Sometimes you do have to read all the datasheet several times before it clicks!

And then look at the examples - after a while the similarities are obvious - take the example in fig 21 - this has the wider pinout, but we can easily compare to the 8-pin version elsewhere

1657295980714.png
 
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