Load test fixture using a load cell?

First off I'm totally new to Arduino, I have zero experience in the platform. I have a project that requires a a device to be tested via repeated physical force loads and although testing equipment exist to perform this with ease, the cost is in excess of $3K for a automated motorized test stand with a load gauge and since the test needs to be repeated cycles, I'm looking at going this direction opposed to just doing hand measurements which could easily be done with handheld load gauge.

The plan is to use a load cell mounted to a linear actuator mounted in a vertical fixture. I need to apply a fixed load with a cycle count at X number of times and have the linear actuator automatically cut off at the predetermined load back off and then apply the load again up to and/or beyond a cycle count of any value. Can anyone give some advice on this, way too complex for a beginner or any tutorials of similar requirements?

I have located a linear actuator with feedback and a built in potentiometer as a start along with several load cells.

Thanks!

Hi, This looks feasible OK.. Maybe give us more details of all the devices??

Some of the components:

Arduino Board Uno?

Linear Actuator

http://www.pololu.com/catalog/product/2305

Load Cell or Force Sensor Options

http://www.phidgets.com/products.php?category=3&product_id=3102

or

http://www.phidgets.com/products.php?category=3&product_id=3135

There are more options for load cells, but these are two that seem to be within the budget.

Aside from the mechanical mounting which would be two aluminum plates bolted in a 90 degree vertical orientation or a 80/20 rig, that's about it.

Could you be more precise in how you're testing? Are you stretching something or smashing it? What load range are you looking for (how many pounds of force) and what precision do you need?

Chagrin: Could you be more precise in how you're testing? Are you stretching something or smashing it? What load range are you looking for (how many pounds of force) and what precision do you need?

It would be a force test on the face of an object to test the capabilities i.e resistance to various loads. Load range would be 0.5 to 15 lbs.

Basically I want to make something similar to what's capable from the instruments listed below:

http://www.shimpoinst.com/FGS_50PVH.php

http://www.shimpoinst.com/dart_2.php

I don't need to replicate these devices 100% just what's listed here:

minimal:

-ability to reach the set load point and return for another cycle. -ability to adjust cycle count to do repeated testing in succession.

would like but not required:

-speed control -ability to control dwell time at maximum load setting in time -calibration setting

So there’s three parts to your project: A) interfacing with the linear actuator, B) interfacing with a load cell, and C) a bunch of programming to control it.

A) The Pololu linear actuator is pretty well documented as are all of their motor drivers. About the only thing they don’t really help you with is which motor driver to use; make sure you check the “specification” tab on the actuator’s product page and note the “stall current”. You will need a motor driver capable of putting out power up to that stall current.

B) The load cell is a bit harder. First off you don’t want to use that “Flexiforce” sensor; if you note its specifications it’s only accurate to 5% of its load range. In other words the 100lb sensor can’t tell much difference between a 5lb and 10lb object.

What you need is a load cell for decent accuracy. Here’s a good writeup of how to interface with one. About the only thing he doesn’t show is how the load cell is mounted; here’s a good picture of one with a typical mounting. Finding where to buy one economically is a bit trickier because most sellers cater to corporate buyers with the associated high prices. What you might want to try is buying a cheap, electronic bathroom scale and scavenging the load cell from it. With respect to the instrumentation amplifier you can find these at electronics sellers like Digikey, Mouser, or Newark (~$6).

C) If your goal is to just run a simple, repeated testing of a given load then it would probably be easiest to rewrite your sketch each time and kick it off or stop it with a single button interface. The program would be pretty small: loop between driving the linear actuator and checking the load until the desired load is reached, stop the actuator, pause, retract the actuator, then repeat. I suppose for someone who never does programming that might be complicated but you can always find some help in the forum if you get stuck (just gotta post your code and give us a place to start from).

Chagrin: So there's three parts to your project: A) interfacing with the linear actuator, B) interfacing with a load cell, and C) a bunch of programming to control it.

A) The Pololu linear actuator is pretty well documented as are all of their motor drivers. About the only thing they don't really help you with is which motor driver to use; make sure you check the "specification" tab on the actuator's product page and note the "stall current". You will need a motor driver capable of putting out power up to that stall current.

B) The load cell is a bit harder. First off you don't want to use that "Flexiforce" sensor; if you note its specifications it's only accurate to 5% of its load range. In other words the 100lb sensor can't tell much difference between a 5lb and 10lb object.

What you need is a load cell for decent accuracy. Here's a good writeup of how to interface with one. About the only thing he doesn't show is how the load cell is mounted; here's a good picture of one with a typical mounting. Finding where to buy one economically is a bit trickier because most sellers cater to corporate buyers with the associated high prices. What you might want to try is buying a cheap, electronic bathroom scale and scavenging the load cell from it. With respect to the instrumentation amplifier you can find these at electronics sellers like Digikey, Mouser, or Newark (~$6).

C) If your goal is to just run a simple, repeated testing of a given load then it would probably be easiest to rewrite your sketch each time and kick it off or stop it with a single button interface. The program would be pretty small: loop between driving the linear actuator and checking the load until the desired load is reached, stop the actuator, pause, retract the actuator, then repeat. I suppose for someone who never does programming that might be complicated but you can always find some help in the forum if you get stuck (just gotta post your code and give us a place to start from).

Thanks a bunch for the info and help, will be very helpful in this project.

Judging by the specs of the linear actuator for this project, I'll probably lean towards this motor controller:

http://www.pololu.com/catalog/product/1393/specs

So the Uno board is the best option for this? I would like to get a board and start familiarizing myself with the code aspect as well.

code101: Judging by the specs of the linear actuator for this project, I'll probably lean towards this motor controller:

http://www.pololu.com/catalog/product/1393/specs

So the Uno board is the best option for this? I would like to get a board and start familiarizing myself with the code aspect as well.

That motor controller and an Uno would be fine for this project. You will want to take a look at the documentation for that motor controller with note of the serial protocol that they use to control it. If it seems complicated to you then you might want to look at a more straightforward driver like http://www.pololu.com/catalog/product/1451.

The feedback mechanism that the Jrk12v12 motor controller provides is pretty simple to replicate with the Uno.