Method and feasibility of wiring in a scale to arduino?

Projects General Guidance
1

Hi guys, my background is mainly in industrial robotics programming and a bit of controls programming as opposed to arduino so pardon if I sound ignorant.

I'm looking to create an automated setup in which a part falls down a drop chute cylinder into a series of slots in a turn table. The turn table turns until the loaded parts falls through a cut out hole in it's floor onto a scale. The scale then sends the recorded weight to the input of the arduino board. Through the equivalent of an "IF" command the part is determined by programming logic to weigh within a given parameter or not. If it passes this parameter a seperate motor spinning a mechanical arm knocks the part off the scale into a bucket by command of the arduino output and returns to it's position. The turn table then rotates to pick up and drop a new part on the scale by an output command from the arduino board. If the part is ever found to be outside the parameters required during the scale measurement an audible simple beeping alarm is sounded by an output command and the entire process is halted by the controller logic.

I plan on using a scale like this: Ultra Precision Scales with Super Sensitivity and SAW Technology - Arlyn Scales

Which claims to have these options for outputs to the controller:

Analog Output 4-20mA (or 0-5VDC)
RS-232 Serial Port
USB Communication (w/ Virtual Serial Communication)
Ethernet TCP/IP Connectivity
WiFi TCP/IP Connectivity (UpScale)

Is this set up feasible, and by what method should I go wiring the scale to the arduino mega? I know nothing about programming arduino nor how to correctly physically set up it's inputs and outputs, but if anyone could give me some advice and point me in the right direction that'd be much appreciated. Thanks!

2

You may be better off using a simple load cell rather than have to hack into an unknown device.
There are ranges that will suit your load requirements.

If the part drops onto the measuring table, you will probably have to allow a settling time for the load cell to give the correct weight as opposed to the drop force applied.

Then it would be a matter of writing the code to compare the measured weight to a reference go/no go.

Many examples around, this is just one.

3

To me, the RS-232 interface looked easiest to deal with. You would need an RS-232 to TTL converter, but they're available dirt cheap. All you'd have to do is wire the converter's output to the any one of the Arduino Mega's UART lines. I would suggest not using UART0 as it is used by the USB interface. Programming them is a breeze with built-in functions. What you would have to figure out is how to parse the incoming data.

Arduino's Serial reference

Here's an example of what you could buy:
RS-232 to TTL Adapter (Amazon)

4

What you are trying to do is straight forward with an Arduino or indeed any microcontroller. I assume the mechanical side is something you are capable of.

You will need to learn to program an Arduino, there are plenty of tutorials on here, in the IDE and elsewhere. While not a structured teaching package they are intended to give a complete novice what they need to learn to program a microcontroller successfully.

You will get help here if you are clearly making an effort but have got stuck. If you want someone to do this for you then ask a moderator to move this to gigs and collaborations and indicate how much you are willing to pay.

Good luck with your project.

5

bluejets:
You may be better off using a simple load cell rather than have to hack into an unknown device.
There are ranges that will suit your load requirements.

If the part drops onto the measuring table, you will probably have to allow a settling time for the load cell to give the correct weight as opposed to the drop force applied.

Then it would be a matter of writing the code to compare the measured weight to a reference go/no go.

Many examples around, this is just one.

https://www.youtube.com/watch?v=S12Mp8gDJmI

A load cell isn't going to be accurate enough for what I need. I need to be measuring within a range of about .0002 lbs, meaning the scale I need will have to be pretty high end and fast functioning. Like I said, the one I listed has a lot of dedicated output options, but knowing which is feasible for the arduino mega controller is where I'm stumped.

Pippadi:
To me, the RS-232 interface looked easiest to deal with. You would need an RS-232 to TTL converter, but they're available dirt cheap. All you'd have to do is wire the converter's output to the any one of the Arduino Mega's UART lines. I would suggest not using UART0 as it is used by the USB interface. Programming them is a breeze with built-in functions. What you would have to figure out is how to parse the incoming data.

Arduino's Serial reference

Here's an example of what you could buy:
RS-232 to TTL Adapter (Amazon)

So after the conversion of RS232 to TTL, would the data coming in be readible by the arduino board? It sounds like it's not that simple, and I'm not even sure where to correctly wire in a TTL input to a mega board. If there are any tutorials to that part alone or you just want to straight up tell me that'd be really helpful.

PerryBebbington:
What you are trying to do is straight forward with an Arduino or indeed any microcontroller. I assume the mechanical side is something you are capable of.

You will need to learn to program an Arduino, there are plenty of tutorials on here, in the IDE and elsewhere. While not a structured teaching package they are intended to give a complete novice what they need to learn to program a microcontroller successfully.

You will get help here if you are clearly making an effort but have got stuck. If you want someone to do this for you then ask a moderator to move this to gigs and collaborations and indicate how much you are willing to pay.

Good luck with your project.

The mechanical side is something I will have no issue with. I have that worked out. It's the arduino related stuff that I'm fuzzy on. I will check out the tutorials section and report back. It's good to hear this project sounds feasible so far. I'm not asking anyone to necessarily do this for me, but simply looking to get pointed in the right direction of where to start learning how to do all of this myself. If I get stuck, perhaps I will pay someone to do it, but for now I'd like to expose myslef to the language. Is arduino simply C++ or something more proprietary?

6

Is arduino simply C++ or something more proprietary?

It's C++ using GCC as the compiler.

In order to help complete beginners there is a pre-defined setup() and loop() function to use. There are also lots of predefined functions for useful things, look in the resources / reference section on this web site. There is also the serial monitor in the IDE, which makes printing test and diagnostic data dead easy.

Just don't get into the habit of using delay() all over the place :o

7

You mean like:

:grin:

8

The scale you linked looks like it would work for what you want to do. The manual is not terribly detailed on the exact data format used on the RS232 port, but the scale can be put in a mode where it automatically sends a weight reading when an object is placed on the scale and the weight reading has stabilized. All the arduino would need to do would be to wait for a weight reading to be received on the serial input, and then check the weight value against your criteria and perform the needed action.

9

germanicus:
A load cell isn't going to be accurate enough for what I need. I need to be measuring within a range of about .0002 lbs, meaning the scale I need will have to be pretty high end and fast functioning. Like I said, the one I listed has a lot of dedicated output options, but knowing which is feasible for the arduino mega controller is where I'm stumped.

Fair enough...btw, range is from x1 to x2 or similar.
I missed your link as it is usual to add any links using the tool above, more noticable.

I see they have a variety of add on alternatives for output, one being 4-20mA or 0-5v.
Not sure any of those options would be suitable as analog doesn't normally give a stable signal unless using averaging but then precision goes out the door.
I'm surprised with such a high-end price they do not have a digital output which would be a much better addition option.