Speed and torque using lab view

[Quincie]

I'm building test bench, with dc motor as a load and another motor as a sample. how do i measure toque and speed using lab view? which hardware can I use?

[Questionmarker]

usually you set the motors to a certain speed. For torque; well if you want to measure this, make sure you have a motor that allows for that...

Anyhow; if you want to measure sth. with LV you need a sensor able to measure this entity. Then, you have to make sure that you can get these data to the computer, e.g. a A/D card. When you can use it with LV you are fine.

If I did not answer your question, maybe describe your problem with more details?

[Wayne.C]

Quincie,

Do you have a load cell picked out to measure the torque? 

[Broken_Arrow]

Torque sensors can be expensive, so plan for that. You'll need to decide between rotary torque or reaction torque. Here's a simple write-up on rotary torque sensor use.

As far as LabVIEW is concerned, you'll need more hardware to integrate the sensor to your computer. Many torque sensors have a 4..20mA out, or 0..5V out. The latter is a piece of cake - a low-cost USB DAQ can read that. I can recommend some, but do you already have electronics picked out? If you use a plain load cell for torque, as Wayne asked about, then you'll need different front-end electronics.

As for speed, you may use an RPM counter, or an encoder. Many many options. Some rotary torque sensors have encoders built-in.

Be more specific as to what you want to learn about.

[Quincie]

Thanks a lot guys. for torque and speed I will try your recommendations. 

Second Question?

How do I brake my load automatically? I want to use 12V small dc motor as a load.

Actually I'm looking for low cost components, this is my school project.

Thanks.

[johnsold]

Quincie,

A motor also acts as a generator so one way to brake a rotating motor is to connect a resistor across the motor.  The energy stored in the rotational inertia of the system gets converted to heat in the resistor.  Since this is a school project, you get to calculate the energy, the power, and the specifications for the brake resistor.  Do it well and impress the instructor.

Reversing the load motor can also decelerate the system.  You still need to dissipate the energy, so give some thought to where it goes.

Lynn

[Quincie]

Thanks very much Lynn. I've also thought of using resistor as a load but I thought I won't able to control it with lab view,

How do I control load with a resistor as a break with lab view?

Thanks.

Q

[johnsold]

You could use a power transistor as a load. The gate voltage or base current can be varied to change the load.  You could have several resistors and switch among them with relays. You could vary the field current in the load motor.

You could probably find several other ways to vary the load.

Lynn

[Quincie]

Thanks Lynn.

[Quincie]

Hi Guys.

What's the best small 12V DC motor can I use as load/generator? I mean generator/load with no cogging coz I also wants to test small dc motor with low torque.

Ta