Simon

I can only offer these as general suggestions, but it sounds like an isolation/grounding issue. Does the failure correspond with any particular event, such as a thunderstorm, or machine cleaning cycle? There's a lot of experience and engineering behind a good wiring design that avoids isolation and grounding problems. So that is best solved with local hands-on expertise Some points to note: * If solenoids are being used ensure they have a flywheel diode fitted. Use Solid-state relays for isolation, not mechanical relays. * If variable speed drives are used, ensure the motor cabling is physically separated from all control, signal and comms cables. Use shielded cables and RFI/EMI filters as specified by the drive manufacturer and relevant wiring standards. * Ensure the CAN bus comms is powered separately to the IO devices. It is best to use a 4-wire CAN cable and supply CAN bus power from the PLC end. Don't power the CAN interface of the EX-RC1 from the same local power supply as the IO devices. * if the remote EX-RC1 system is on a generator/battery/solar system, consider installing a DC-DC convertor or a small UPS, that gives clean power to the EX-RC1. I hope this helps.

You can quite happily poll Modbus registers using RS232. It's just that you can only have one slave and it can only be 25 feet from the master. Also, I have found that even if the Unitronics COM port has been set up for RS485, if you plug a standard RS232 4-pin cable in it will still talk RS232. The post from Cam suggests putting the PLC into stop mode, which is a good thing to try. That will prevent any settings in the project (such as Modbus) from taking over the port. You can view and if required set comms parameters via the info mode and the project won't override them while in stop mode. If you still have no success, I suggest trying bootstrap mode (power down the PLC, hold your finger on the touchscreen and power up, then follow the prompts). This will isolate any effects of the OS and program. In this mode you must have Visilogic set to 115200 baud and you won't be able to upload the project in this mode. This will at least confirm whether you have comms to the PLC. It is also possible to lock out Visilogic communications, see old forum post below: http://www.unitronics.com/forum_old/topic.asp?TOPIC_ID=2034 If you can get into the info mode you can check and if needed change the value of SB314

Nice idea, like a logic analyser chart. I have been asked about this before as well. The workaround is to put in some logic to set an MI value as 0 or 1 based on the value of the digital input. Then add that MI to the trend.

Hi Rocky, you need to create the image cache file. It then gets stored on the local PC. With the PC that is working OK you (or someone) must have created the image cache on a previous occasion.

Hi, The CPU does not consume one of the IO slots. So you can have a CPU plus 5 IO modules. The capacity of 5 modules are the narrow style. You would like to use the UID-W1616R which is a wide module and they are 1.5x wider than the narrow ones. This is equivalent in width to 4.5 narrow modules, so you are OK, but won't be able to fit any more modules directly on the PLC.

I am not aware of any timeframe for the M91 ceasing production. However I think it is fair to say the writing is on the wall, in that it is now the oldest family of Unitronics PLCs still being promoted. For new applications I usually recommend either the Jazz or the V130. If expansion is not needed, then the Jazz is fine. Otherwise it's not a huge jump in price to go to the V130. The Samba35 may also be an option. I hope this helps from a strategy point of view, however I am also keen to hear of any definite timeframe.

Can I just add a vote from the non-US lands - can you consider a design that will handle 240VAC as well as 120VAC? I don't see a huge demand, and it's often not a big deal to use interposing relays, and customers like to "upgrade" from 240VAC logic to 24VDC logic because it is safer. But if the cost of increasing the voltage rating is not high then it will make the module more universal. It is frustrating to see a potential solution then find out it only accepts 120V.

I was discussing this with a colleague just last week. I number my steps in 10's and use store functions. As above, it allows additional steps to be inserted. It also allows steps to be executed out of order. As much as I like to think I know the project from the start, I have never used an incrementing index for this, since it is such a rigid framework. With Visilogic I use a subroutine per step and use a compare block to call the subroutine when that step is valid. With U90 Ladder I use jumps to execute the current step and jump over the others. Hope this helps.

Great example of breaking into the traditional territory of the "big players". I would love to see this application story once it is published.

In general terms you can use a loop-powered device with Unitronics if you include a loop power supply in series with the loop. It is simple if there is only one analogue device connected. However in this case you may still get problems with the reference ground, depending on the overall circuit for your second analogue signal. If it's not a simple case of switching sensors as Alex suggested, I would put a signal isolator on the loop-powered sensor. Either purchase an isolator with support for loop-powered sensors, or add a loop supply to the sensor circuit. Adding the loop power supply in this case should not affect the reference ground as the isolator is between the PLC and the loop supply.

Hi Greg, I didn't try to compile mine, looks like I didn't go far enough. I'm still curious why UINTs arent allowed as inputs for formula and conversions.

I note that the INT to REAL function in the math menu only allows signed integers. Question for the creators, why not UINTs as well? My favorite solution is to use a multiplier block, multiply your UINT32 by 1 and store the result into a REAL. I checked and the software lets you do this. You could then save this as a UDFB if you so choose.

The order code for the cable that normally ships with the PLC is actually RS232-CB1. The part MJ10-22-CS25 is just the adaptor that plugs on the end. You would need to contact a Unitronics distributor, check the Unitronics website for your nearest one.

When you configure an RTD, the linked MI contains the actual temperature value, scaled to tenths of a degree. eg value 254=25.4degrees. There is no need for additional linearisation. Just make sure you use the correct coefficient value for your RTD.

If the IP address is a firewalled, private IP address, you will not be able to ping the modem directly. When the modem is connected in GPRS mode the Unitronics examples normally display the IP address, or you can view it in hyperterminal. If you can ping this IP address, then it would appear you have a public IP address on the SIM card. Assuming this is the case, if you change the example to set up the GPRS in listen mode, you should then be able to connect from Visilogic using the Ethernet call method. However I would also try the recommended method first, that is getting the PLC to initiate the call to a PC in Listen mode. This is simpler and helps confirm that all the basic steps are correct. Without trying to be unduly negative, this process works well when it works, but is not "plug and play". It usually takes some testing and debugging.

Just a note on PID, you can select the sample time of the PID - I would suggest experimenting with this. You mention "wait 10 minutes" between adjustments, so maybe set the PID sample time around 2-5 minutes? (I haven't checked that it allows that setting, but hopefully you see where I am coming from).

The main issue is not anything inside the PLC or Visilogic - it is with the way telco providers handle IP addresses with GPRS connections. With GPRS (and other types of cellular broadband) the remote device can call out to you, but you can't easily call into it. So the PLC can call back to your PC easily. But if you put the PLC into listen mode and try to call it from your PC, the PLC will never receive the call. This is because the GPRS connection does not allow you to call the remote device. The IP address that the modem is given on the GPRS connection is usually a firewalled, private IP address, on its own subnet. Exceptions are: * public IP address on SIM card and use dynamic DNS * fixed, public IP address on SIM card * use a VPN If you don't have any of these exceptions available to you , then your only option is to have the PLC initiate the call and have your PC in "listen" mode.

I would put a DC-DC convertor (24V in - 24V out) between the batteries and the PLC system. Check the specs of the convertor and try to ensure it has a fast cutoff on the output once the input voltage falls below the accepted minimum. The convertors usually accept a relatively wide input range and provide a regulated output at 24V. If you connect the PLC directly to the batteries, as the battery voltage sags below 20V it is highly likely to corrupt the RAM and/or flash memory on the PLC. We see it mostly when the PLCs are installed on vehicles, since the starter motor causes significant voltage drop when starting the engine.

I'm not Joe, but my thoughts are as follows: The diode solves the problem by conducting normally, via its forward path. The MOV solves the problem by conducting "abnormally" via its breakdown path. A MOV can only sustain a finite number of breakdown events before failing. To me the diode is an inherently more robust method for protecting against this type of spike that you know will keep occurring. The diode is more of a preventative measure rather than a protective measure. A MOV is more typically used on applications where you can't prevent the spike from occuring, but you must limit the damage it causes.

Do you have a specification for the analogue outputs of the ADM (or the inputs on the VDO gauge)? Automotive signals don't usually play by the same rules as industrial signals. I would also try to measure the signal with a multimeter, starting on the voltage range.

Joe, from my recollection, the -CS26 is just the old version of the -CS76. Did you mean the CS25? The CS26 was used for 9-pin modems before the Jazz was released. Post-Jazz we needed the CS76 to supply power via pins 1 and 6 to the Jazz comms adaptor. If the scales are wired as a DCE (modem) then the CS26 or CS76 is needed - no crossover If the scales are wired as a DTE (PC) then the CS25 is sufficient. If it's just a 3-wire port (RX, TX and GND) all you need to do is swap RX and TX if it doesn't work first time. This is why I suggest turning off hardware handshaking/flow control at both ends if possible.

I think this forces you to use the EX-RC1 both for the speed of update (10ms) and the number of I/O drops (30). The EX-RC1 and UniCAN are very fast, I think it has been stated in the forum elsewhere that the I/O exchange can occur in a single PLC scan. This may be only for a single UniCAN slave. If you need to read all 30 slaves within 10ms you may need to ask Unitronics support for help directly (support@unitronics.com). Also, the UniCAN protocol allows you to create event-driven updates, so the remote module can send data to the PLC as soon as an input changes, instead of waiting for the PLC to request an update (as occurs with Modbus). I hope this helps.

The engineer in me says this is likely to be possible, but complex and time consuming to get it working. It is certainly not a built-in feature of the V570 or Vision family of PLCs. If it could be made to work it would be difficult to support. The businessman in me says no, don't do it. Some alternatives could be, depending on what you are trying to achieve and what your limitations are: Use an SMS modem on the PLC and send to an SMS-to-email gateway. Send emails from the PLC and send them to an email to SMS gateway

For example, go to Visilogic, the "Store" menu and see "Store Indirect" element.

I have also had this type of feedback. So far I think it is better that we have the product now rather than wait for a complete set of written documentation. That may change if someone really chews me out over this... Just wanted to also point out the youtube training videos (search for the Unitronics youtube channel). They are not a substitute for a written document, where you can search a find specific topics, but they have helped me on a number of occasions, and do contain some nice little detailed points.