# Using Modbus over Ethernet to connect a weigh scale

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#### hemal

We have a weigh scale with MODBUS on RS 232. We are connecting to a PC and operating on PC. Though we have been able to communicate from the PC to the scale through serial port, we require to communicate to the modbus via Ethernet

We tried at our end by using a few softwares that are supposed to convert serial Modbus to Ethernet so that we could communicate to Modbus through serial... It did not work

There are some serial to Ethernet hardware devices but are quite expensive and will make the solution cost high

Can you help us out in this .. Have you come across some serial to Ethernet gateways for modbus

Do you know of someone who can help us in this ?

[email protected]

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#### Steve Myres

The hardware devices will work fine, and if you take into account the integration cost, are inexpensive for a one-off solution.

If you truly do need low unit cost (because this is a product you manufacture for sale, say), then you have engineering money available to design and build your own equivalent to the hardware device. Also, if it's a standard product for sale, don't forget to check and see if the scale manufacturer has an option for Modbus/TCP. Most seem to. That would be cleaner and should be cheaper than buying the bridge and less hassle and risk than rolling your own converter.

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#### Lynn August Linse

Do you MAKE the scale, or are you just using some made by someone else?

The cheapest Modbus/TCP to RTU converter I am aware of is the Digi One IA at about $180. (http://www.digi.com/products/serialservers/digionesp). I am sure there are other options by other companies (Moxa, Lantronix, HMS, others). You you make the scale, then there are 'Modbus/TCP in a CAN' solutions which look like slightly large RJ45 ports. These talk Modbus/RTU on some TTL-level pins, and Modbus/TCP on Ethernet. For example, the http://www.digi.com/products/wirele...olutions-on-module/digi-connect/digiconnectme, although again other companies make such things (Lantronix and HMS both do). H #### hemal Thanks for the quick replies. My apologies for not being fully clear We make the scales. While we have made a lot of scales with MODBUS, the integration part is usually left to the system integrator or through 485 which allows multiple scales to be connected to a single PC/PLC This is a new project where client has asked and we are trying to develop a complete solution for using using multiple scales through 232 and wants to connect through ethernet (its not specified why they specifically want through ethernet). True the hardware suggested would probably work, but the landed cost of such hardware works out to over$350/- in India which is more than the cost of the scale (yes we provide scales at such low cost)

Was wondering if something else can be done

[email protected]

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#### Eamonn Wallace

Well if I were looking at this, short of designing an Ethernet port onto the board of the scale electronic, I'd look at a Single Board Computer type solution. an SBC with serial ports and Ethernet connection will do the job nicely. I've used rabbit SBCs in the past for such projects but there may be cheaper and better solutions now.

No matter how many ways you try to look at this you are constrained by the number of serial ports you can provide.

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Regards
Eamonn Wallace

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#### Dixit Solanki

Hi, Hemal,

Can you please elaborate in more detail?

You are the scale manufacturer.
Are you also manufactures the electronics hardware for the scale like Main CPU PCB, Micro-controller model number, programming of Controller etc. Or you just outsource the electronics PCB part?

In my current Product hardware, I have already replaced the serial by native Ethernet.

Thanks,
Dixit Solanki
[email protected]

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#### hemal

We manufacture the main electronics in house.

Yes, there are a number of external hardware products that can achieve what i want. The problem is their cost in India

Was thinking of linking all the machines through 485 to an inexpensive Atom palmtop and then linking that over ethernet. This would cost $200/- landed as compared to$ 450/- landed for the converters. Has anybody tried this?

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#### Eamonn Wallace

> Was thinking of linking all the machines through 485 to an inexpensive Atom palmtop and
> then linking that over ethernet. This would cost $200/- landed as compared to$ 450/- landed
> for the converters. Has anybody tried this?

yes, sort of, I've used SBCs to do it...

One thing springs to mind you'll need some sort of addressing scheme and a polling scheme too on the weigh equipment otherwise you won't get it to work properly

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Regards
Eamonn Wallace

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#### Andrzej

Hello,

You can use MMNET01 from www.propox.com.

It is low-cost and easy to program the Modbus RTU to Modbus TCP/IP converter.

Regards,
Andrzej
www.modbus.pl