Search results

Another, although less likely, cause of what you're observing could be that the IQ SensorNet's RS-485 circuitry is partially damaged - either transmitter damage, unable to sufficiently drive one or both of the RS-485 lines, or receiver damage, where the device is presenting a very high load...

From your details and tests, this appears to me to be an electrical issue. My first two thoughts are either grounding (i.e. RS-485 common-mode (0V) reference) or something to do with termination/biasing. Starting with grounding, are you wiring your RS-485 connections using 2 wires or 3 wires...

You can't. Modbus RTU can only have one master per RS-485 bus. You would need to use the 2-port 3280 or the 4-port 3480. Another option would be to use one 3180 per Modbus RTU master.

Is the PLC necessary? The industrial PC running NodeRed may be able to directly communicate with the Molding Machine (using Modbus, for example), then push data out to a cloud server (using MQTT, for example), while simultaneously serving up a dashboard on the display.

I can't comment specifically on the Matrikon OPC server, but there are a couple other limitations based on the protocols being used (RS-485 and Modbus RTU). Electrically, RS-485 allows up to 32 Unit Loads to be connected to a single bus. While historically, each device would be 1 Unit Load...

Start a new thread and ask specific questions. The more details and context you provide in your questions, the better answers you will receive.

If you can't add a second slave ID, I don't see how adding a second MGATE helps. All you would be doing is multi-dropping two MGATE's. However, a single MGATE already has the ability to support multiple "virtual" Modbus devices. There is no difference between one MGATE routing two slave ID's...

I'm trying to understand your situation. Here's what I gather from your post. Your DCS communicates Modbus RTU (or ASCII) via RS-232. You have a Modbus/TCP Server (Slave) device that exposes a primary controller at one IP address and a secondary controller at another IP address. When the...

Another point to consider is from a design perspective of the VFD. There is a performance hit when using floating point numbers, and the associated floating point arithmetic, compared to integer numbers and arithmetic. And, as was already explained, while floating point allows you to express a...

Thank you for the follow up video. It does certainly seem like the VFD's RS-485 circuitry is damaged, as it appears the adapter's voltage levels swing the full range and the same phenomenon of reduced voltage on the RS-485 - line occurs with your spare USB to RS-485 adapter. Perhaps you can...

Thank you for the video. I'm assuming Ch1 (yellow) is RS-485 - and Ch2 (blue) is RS-485 +. I'm also assuming the transmissions from the VFD have the larger voltage swing and greater delay, compared to the transmissions from the Waveshare adapter (although there is a chance this assumption...

What is the vendor and model of the heat pumps? Can you attach a user's manual for the device?

You can only change the slave ID using CASModbusScanner if it is available via a Modbus register exposed by the device. Can you attach the complete register list for the heat pump (or at least the vendor and model number)? There are a few common ways that the slave ID is set on Modbus devices...

What settings are you actually changing? The settings I was describing can be found in ModScan by clicking Connection->Connect, then in the Connection Details window, click Protocol Selections. Here is what it looks like: I'm also concerned that you may have changed other settings in ModScan...

The value itself is irrelevant to the communications. The fact that ModScan shows any value besides 0 indicates it received at least one valid response from the heat pump. The reason ModScan is showing a negative value is because of the display options you've selected. If, for example, you were...

Do you have all 3 heat pumps connected to your USB to RS-485 interface? If so, they must all be configured for different slave addresses, otherwise they will all try to respond at the same time. Since you are getting valid data sometimes, this could be a timing issue. In ModScan's Protocol...

And what are the LED's on the flow meter doing? You may need to contact that company tech rep again. If the flow meter indeed uses those two wires for both power and a pulse, I don't see how you could put such a large resistor (22k) on the positive supply voltage. Any significant current draw...

What you are observing indicates that termination is still connected. According to the Waveshare wiki (https://www.waveshare.com/wiki/USB_TO_RS232/485/422/TTL#Matching_Resistor), the converter's termination resistors are controller by jumpers inside the unit and are on by default. Take the unit...

How are you powering the flow meter? The data sheet (https://s3-us-west-2.amazonaws.com/catsy.467/qs100-data-sheet.pdf) implies that the two wires are used for both pulse and power: What are the LED's on the flow meter doing? Refer to page 12 in the User's Manual...

The uneven voltage levels and sporadic communication could be a bus loading issue. What happens if you remove the 120 resistors and make sure any termination settings on the converter and VFD are disabled? Note that with such a short cable, termination is not necessary for this application. The...