tachometer.vi

[labview1958]

I have attached a file about my setup. I need to measure the RPM of the rotating disk with a tachometer. However I cannot afford one. I have build my own SIMPLE tachometer using a torchlight and a photoresistor diode. Can it work? How do I connect the photoresistor to my 6025E DAQ card? Which PINS? I have attached also the PIN sheet.Do you know where I can get a tachometer.vi.?

[AnalogKid2DigitalMan]

Yes, it can work, but will 1 pulse per rev be sufficient resolution? If the motor is going slow, you will get a low frequecy signal, make sure the counter clock on the DAQ card is set appropriately.

What type of motor is being used? You may already have a 'tachometer' of sorts vuilt in if it is a brushless motor.

You can buy IR LED emitters packaged together with an IR photodiode or phototransistor (looks like a [ with a slot in the middle). IR is typically used so it is immune to ambient light. The disk would go within the slot to make/break the light creating a pulse(s) per rev. They typically can run off of 5V which you can tap from the DAQ card. The IR led will need a series current limiting resistor, the phototransistor will need a pullup resistor to 5V. The pulled up output can be wired to one of the general purpose counter inputs on the DAQ card. Search LV help for frequency vi's on how to use counters to measure frequency, rememdber to multiply Hz by 60 to get RPM.

[labview1958]

My DC motor is a HIGH SPEED drill going up to 10 000 RPM. Can the LV program measure that?

[labview1958]

"They typically can run off of 5V which you can tap from the DAQ card"

Can I use an external 5V power source? I do not want to burden the DAQ card.

"the phototransistor will need a pullup resistor to 5V." Why?

"The pulled up output can be wired to one of the general purpose counter inputs on the DAQ card"

I have attached the 50-PIN connection sheet. Where shall I connect?

[labview1958]

I have not been able to lacate a SIMPLE tachometer.VI. I believe it just counts the pulses in one second and multiplies the figure to give RPM. Can you help me?

[labview1958]

Hi everyone!

Do anyone know where I can get a SIMPLE tachometer.vi ?

[Dennis_Knutson]

To count pulses in a certain amount of time is the function of a frequency counter. From your numerous other postings, I know that you have a 6025. This has two 24-bit counter/timers. Look at the DAQ shipping examples for counters and read the LabVIEW Measurements Manual that is part of the LabVIEW Bookshelf. All of this should be on your pc and available from the LabVIEW Help menu.

Message Edited by Dennis Knutson on 03-08-2005 07:21 AM

[djs_at_eaton]

The Tachometer I attached is pretty simple. I haven't tested it at high speed. It runs from a quadrature encoder and works to at least 300 RPM. It uses the counter / timer chip on a 6031 DAQ card. I have a program using this that runs for months at a time as part of an endurance test.

There are some very simple routines using toothed wheels if you don't need direction. If you want true high speed and direction AND easy zero speed detection, then you need to buy a tachometer-generator. It's a linear DC generator that gives a voltage proportional to RPM. Just run the output into an analog channel and scale it.

[labview1958]

Hi,

I have attached the measure frequency VI that is simple for my work. Would this be okay? It would used to measure the frequency of a incoming TTL signal. Can I RUN this VI all the time together with another VI which generates a pulse? If I want to measure the current frequency would it slow or halt the pulse being generated by the other VI?

[Salvador_Santolucito]

Hi,

I see that this is a Traditional DAQ example. Do you have LabVIEW 7.1? Since you are very new to LabVIEW and DAQ programming I would highly suggest getting the latest LabVIEW. This will allow you to use DAQmx.

You really need to be using DAQmx. It is much simplier and easier to understand. Also, the shipping examples are better in DAQmx.

-Sal