12V Machine Module Dropout

Kevin 5 years ago in IQANdesign updated by Gustav Widén (System support) 5 years ago 1

We have a 12v system with CAN Open devices, and during startup the CAN devices drop out but the module does not, causing errors on screen. The CAN devices are used in safety functions, therefore according to the MC43FS manual, we cannot use the battery voltage as an enable function for enabling comparison channels. Does anyone have any suggestions to prevent the error during startup?

I think you could use your idea of monitoring the system supply using the MDGN +BAT channel, you'd just need to be cautious about how you design the startup conditions for your safety function. 

If you use the +BAT measured on the IQAN master to disable the Generic modules, the GFIN and GPIN will be in disabled status with GPIN values set to their defined error values. 

Further down the chain where you use the compare channel, the compare channel will see the disabled status on the GPIN and get status input error. 

To handle this, you'd need to disable the compare channel, for example based on the status from the GFIN. Disable is safe, when you actively disable the compare channel its value is changes to false, just as if it would if it was detecting an error. 

I'd say it is when you enable again that it gets tricky. If you do not use the OK to start property on the compare channel, it could be quite difficult to implement solid startup and restart conditions for the safety function where the signals are used. 

To handle this, my suggestion would be to see if you could bring in the startup conditions for the safety function also in the OK to start on the compare channel.