convert the rpm of an induction motor to a voltage

[Jehan]

Hey,

This is my first post on this forum.

I want to convert the rpm of an induction motor to a voltage between 0 - 10V.

The maximum rpm is 1800.

I've used an optical sensor which has a output of a square wave form of max frequency 30Hz for 1800rpm.

As the pulse is DC with a High voltage of 3V and Low voltage of 0V I use the 14 pin version of LM 2917.

I simulated the attached circuit in proteus and it works. I get a varying voltage according to the varying frequency.

But the circuit I assembled on a project board doesn't work as required. It gives a constant voltage of 0.6V for all speeds of the motor.

Where have I gone wrong? Can you help me?

Further I found that many of the circuits that were uploaded on the internet and which were said to be working by their aurthors did not work on proteus simulation.View attachment 65391

Thanks

 

[Reloadron]

If you want a DC voltage proportional to motor RPM I would use a tach generator along the lines of those found here. If you want to start with pulses from an optical sensor outputting a square wave where frequency is proportional to RPM then run the frequency into a Frequency to Voltage converter and span it accordingly.

Ron

 

[alec_t]

But the circuit I assembled on a project board doesn't work as required.

A common problem with hobby electronics . Have you double-checked all the component connections against the schematic? Is the battery fresh? Is the board a pcb or a breadboard (which might have tarnished or bent pin-sockets)?

many of the circuits that were uploaded on the internet and which were said to be working by their aurthors did not work on proteus simulation

No surprise there!

 

[Jehan]

Ron,

This is for a project and I was specifically asked to implement a non contact method to detect the speed. I read the pdf of the tach- generator and it seems it needs to be in contact to the motor shaft.

Alec,

Ya I am using a beradboard. I use a power pack instead of a battery. I will double check.

So do you mean that the circuits that do not work on simulation software has a possibility of working when implemented in real life?? Thats Great news.

Then I'll go a head with this circuit View attachment 65396

Thanks

 

[Reloadron]

OK, you are using a LM2917 (I missed that earlier, sorry). Can you post the schematic? Never mind I see the schematic. Let me compare it to the data sheet.

Ron

 

[Jehan]

Ron,

I hope you saw the schematic. The one I assembled is in my 1st post.

Thanks

 

[alec_t]

So do you mean that the circuits that do not work on simulation software has a possibility of working when implemented in real life?

Yes. The possibility may be small, but simulation is never 100% perfect.

The connections to the 2917 in post #4 don't look much like the connections of the F-to-V generator shown in the datasheet for the 2917

 

[Reloadron]

Sorry, been a tad busy. I agree with Alec in that I don't understand your schematic after looking at the data sheet. Have you tried working and building from the data sheet?

Ron

 

[Jehan]

Ron,

No I didn't try working on the data sheet. I just made a circuit that was available in the internet. I do not know how to build from the datasheet.

Can you give me a few basic guidelines? I know your busy too.

Thanks

 

[Reloadron]

I would start with page 8 of this data sheet. Unfortunately I use LtSpice and do not have a LM2917 family model. Focus on the Minimum Component Tachometer just as a starter and see what you get.

Ron

 

[ericgibbs]

I would start with page 8 of this data sheet. Unfortunately I use LtSpice and do not have a LM2917 family model. Focus on the Minimum Component Tachometer just as a starter and see what you get.

Ron

Hi Ron,
This zip contains my LTS folder for the V2F's, sorry about all my toy asc files, feel free to play.

Regards
E

 

[Reloadron]

Thanks Eric, many thanks. Been pretty busy of late, the wife had some major surgery.

Ron

 

[WTP Pepper]

For non contact measuring, stick a bit of reflective tape or tin foil on the shaft (not the whole circumference), illuminated with an LED and use the reflection into a photo diode (amplified of course) to measure the RPM.

 

[kinarfi]

Hey,

This is my first post on this forum.

I want to convert the rpm of an induction motor to a voltage between 0 - 10V.

The maximum rpm is 1800.

I've used an optical sensor which has a output of a square wave form of max frequency 30Hz for 1800rpm.


Thanks

What is your sensor looking at? The shaft?, can you add more "spots" for the sensor to see, such as looking at the cooling fins for a higher frequency?
Kinarfi

 

[kinarfi]

duplicate