USB-Serial adaptors

I had to connect to a customers Micro 1500 via a USB to serial adaptor cable. It was terribly slow. We were monitoring the counts from an encoder turning it by hand to check the length for a cutoff saw. I ended up using an older laptop with a serial port. Is there any way to speed the USB combo up or am I just doomed to using the old laptop with the older PLC?

The speed should really not matter on the cable, its in the settings of the CPU, you can use a USB cable or serial cable 9600 or 19200... I think you may have had a setting different

Tom@Pton said:

I had to connect to a customers Micro 1500 via a USB to serial adaptor cable. It was terribly slow. We were monitoring the counts from an encoder turning it by hand to check the length for a cutoff saw. I ended up using an older laptop with a serial port. Is there any way to speed the USB combo up or am I just doomed to using the old laptop with the older PLC?

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What USB to Serial adapter cable were you using ?
Was the USB port you were connected to USB 2.0 enabled ?

Many people recommend the Keyspan USA-19HS as it seems to cope better with the higher baud rates.

daba said:

Many people recommend the Keyspan USA-19HS as it seems to cope better with the higher baud rates.

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I use the USA-19H through a USB port coming out of the side of my monitor to a ML1500 at 38.4k with no issues* up to 25' of cables total, but there are many other factors when you are trying to monitor a high speed counter through a serial port to a window application.

You should be able to ballpark calculate the k-constant of the final driven element and add a test mode with a manual entry to recalculate it from the HMI within reasonable constraints to accommodate variation in the drive-train from original spec at start up but more importantly, years later.

Even if these values are only accessible with RSLogix, it is better than turning it by hand.

*By No Issues, I mean I left it running plugged into a ML1500 sitting on a chair next to my corner desk, running for three weeks, overnight, over weekends, locked the system at night, come back it and it's still online when I unlock it. This didn't happen completely by accident, I had already set my USB ports never to sleep. Other than that, yes, it did happen by simple default actions installing the right driver and updating it giving it comm port preferences.

So, check your USB sleep settings, and/or get a better converter.

I am using a USB Serial cable (Gigaware) and the standard issue 1761-CBL-PMO2 PC to MICROLOGIX Comms Cable.

Turning the encoder by hand was not a problem when connected to a laptop with a serial port. We could watch it accumulate as we turned the wheel. Not so with the USB Serial cable. Turn...wait for everything to catch up...repeat.

I let rslinx do the auto configure and don't do anymore than that unless something doesn't work at all.

I always connect with serial or ethernet in work as I once had a bad experience on a crane with a USB adapter. I was asked to load an old program into the plc AB 500 and it crashed out with a communications fault.
The processor went into fault and we did not have a spare processor this was about 30 mins before a ship was arriving to be unloaded. I had to remove the processor disconnect the battery and shorted out two terminals to reset the memory.
In work we use Tough books these are great laptops but very expensive.
When buying a laptop for programing I would always get one with a serial port.

jlreid17 said:

When buying a laptop for programing I would always get one with a serial port.

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They (serial ports) are going away

I have sold 10,000's of USB cables, it may be the chip sets that I use but I have very few issues, I can not remember the last time I had a customer that had a issue that was the cables fault

It appears to me that the FTDI chip is best - my Omron serial/USB converter has NEVER let me down and it runs an FTDI chip. Not cheap though.

It was well 5 years ago when I had the USB issue at the time I was starting to get into programming, everything was speced and set up by our PLC guy.
I'm sure these leads are very reliable now as you said with amount that you've sold and had very few issues yourself.
We also have other equipment which we have made our own leads up to conect with using the serial port.
Please don't be put off of USB connectivity just make sure you buy a quality lead as has already been recommend.