Compair air compressor on Modbus RTU - How to?

[krispod]

Anyone knows how to calibrate pressure in delcos 3100 controller for Compair. I have a problems with correct pressure reading by controller.

On controller is set load on at 7,5 bar load off at 8,5 bar, what is the problem
Once compressor load off at 8 bar, and sometimes at 7,6 bar , load on at 7,7 and so on.
I've changed the pressure transmitter for new one but the problem still is.

 

[lbebenek]

Delcos 3100 manual

Welcome.

I found on this topic MODBUS Manual for Delcos 3100 controller.

I looking of Service Manual of Delcos 3100 controller.


Can anybody helps ???

Best regards.

 

[rguimond]

I'm still plugging away at this, with very limited success.

I ended up connecting just one compressor to a Modbus to Ethernet gateway. It makes it possible to experiment from my office instead of in the noisy engine room. The gateway is set to Modbus address of 5.

Parameters are 9600 baud, 1 stop bit, 8 data bits, no parity.

I can poll various memory addresses using Chipkin Modbus Scanner by connecting to Node 1 of the Modbus RTU network. I can also read values from the Modbus bridge on Node 5. The gateway is an Automation Direct MB-Gateway - very easy to set up.

I can also poll the same addresses using a Red-Lion Productivity Station, so i know the comms are OK. However, I just get garbage.I've tried offsetting the addresses by 1 in either direction but it doesn't help.

I found a different manual here: http://api.ning.com/files/kYkWoLTW4g9e5jzKrOfOfX52qeQb-OGXXA7EJhGRoc3pc81CVgxlDkYS1yxMKnJksLDDlIXTSQNZCKEloJax4qI308m9J5Ea/Delcos3100ModBusRTUCommandsPublicVersionV1.1.pdf

Some of the memory addresses differ from those in the original copy of the manual I received, but they still return garbage.

If I read holding register 1014h (404116), I should get RPM or Compressor Temperature (depending on the manual I take the addresses from). I don't.

Searches on the internet don't reveal much, and contacting Compair doesn't help because I can't seems to speak to anyone who even knows what Modbus is.

 

[mellis]

OK, this is standard operating procedure for Modbus. If you get garbage, try swapping the byte order. You can usually find this in the gateway config. Swap high/low 16 bit words, swap high/low bytes in each word. One of the four possible combinations will work.

 

[danw]

1) The Compair is no parity. Are you sure you have the same baud rate for both units? Mismatched baud rates can result in garbage.

2) What constitutes 'garbage'? What exactly is the Compair reporting?

You should have some knowledge of what the values should be for the 3 variables above.

Please do a Modbus read for all three of the above values and tell us
a) exactly what the Compair reports for those values, and
b) what you think the value should be
so we can see what is being reported.

3) Byte swaps should only be an issue for 32 bit data, not 16 bit data.

Compair does not use floating point but it does use 32 bit long integers. The data in registers 0004-0006h is 16 bit data which should not need any byte swapping because it is 16 bit data in a 16 bit register.

 

[Brendonh]

www.modbustools.com/modbus_poll.asp

handy piece of freeware for testing comms and quickly changing baud rates and registers etc.