[SOLVED] RPM Sensor Singnal Conditioning Using LM1815

Hi there,

We wanted to design RPM Sensor Signal Conditioning Circuits. We need your comments. Thanks in advance.

We have RPM Sensors like this:


As far as we know this is VR sensor which produces some analog signal when we place this sensor in front of rotating wheel with teeth.

We googled the detail about the sensor signal conditioning circuit and we found that we may use LM1815. This IC is also available with our local supply.

We tried some designing with the help of google and datasheet from ti website.



Sensor is connected between SIG IN and GND terminal, and output of the ckt will connect the Rising / falling edge of Interrupt pin to MCU. The IRS will count Pulses.

1. Please comment on the above schematic if we missing something.
2. We are considering Rising edge for IRS, should we?
3. We don't know about the purpose of PIN 14 RC Timing ckt, can you please explain?
4. We are confused between using REF Out PIN 12 or Gate Out PIN 10, will you please explain?
5. What are the parameters we need to consider with hardware and software for VR Sensor and mechanical assembly like No of Teeth, Resistance between two terminal on VR sensor.. like that?
6. If there is any better approach exists with VR sensors ckt, can you guide for that?

Hi

Is there a reason you are choosing the LM1815? I can point you in the direction of a very robust and low cost solution that I use.

Only two reason why we choose this is:

1. We dont know what else to consider.
2. When we check with VR sensor to google and the inventory with our local supplier we find this cheapest and easiest solution.

So whatever you suggest we are happy to give it a try. (Yet our PCB is not designed, so we can change to any option.

Thanks for your valuable reply gareth-71

Hi

Use the NCV1124

Gareth

Hi gareth-71,

Thanks for your valuable input. Indeed this NCV1124 seems far better to LM1815.

We only needed to check with our local supply for that.

We will give you update after we test the samples.

Thanks again.

Hi gareth-71,

Unfortunately our local supplier dont have NCV1124.
We need to buy from supplier outside our country. Which may take much time.
Can u suggest another part? In any case we are trying for NCV1124.

Meanwhile We tried LM1815, but in Open terminal there are much noise output, so it gives false reading. Also at motor / Teeth wheel stopped.

Hi,

some VR sensors have all signal conditioning build in. They are based on Hall+Magnet, single ICs contain the complete sensor, except magnet. If you consider to build the VR sensor yourself I can point you to a solution ( **broken link removed** ).

Enjoy your design work.

Hi HTA,

Firstly thank you for your reply and solution. But here we don't have scope of supplying VR sensor made by ourselves with our design. But when we have such requirement we will definetly put your solution a try. Meanwhile the link which you have posted shows "The content you requested not found" page. Please give another try for other people reference.

Thanks again.

Hi and thanks!

Sorry, the article has move to: https://edn.com/design/sensors/4324812/Speed-acquisition-made-simple .

Enjoy your design work!

Hi there,

Find here the VR sensor interface using NCV1124



Please review it and comment. We are yet to receive the IC (NCV1124), so testing will be done later. Meanwhile pleasure to have any helping hand. Thanks in advance.

Please explain the diagnostic mode. We understand this:
After power up with DIAG_IN = GND, observe that both OUTPUT is HIGH.
Again CHANGE DIAG_IN = VCC and check for both OUTPUT = High.
IF both cases are true than sensor connection is ok Otherwise fault.