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Answered

XA2 DOUT problem

Stefan Hedlund 2 years ago in Expansion modules / XA2, XS2 updated by Gustav Widén (System support) 2 years ago 1

I have encountered a problem with DOUT on XA2 modules. We operate several Parker D1VW (NG6) valve, with multiple XA2 modules. Some DOUT (from different XA2) does not activate the magnet coil, although it looks completely correct when I'm connected to IQAN Design . DOUT = Tru.

We use valve contacts with zener diodes, it works on most DOUT otherwise. I had to change the output to PWM instead and then it works without a problem. Is there any problem with the XA2 modules, or are the Zener diodes that do not work against XA2?

Answered

You should use plugs with regular diodes, not zener diodes. 


A plug with a zener diode can be effective for cutting the transient when you power the coil via e.g. a relay. 

For protecting the high-side driver of an XA2, a zener diode is not effective. The XA2 DOUT high-side driver over-voltage protection will cut the transient at a voltage that is below the breakdown voltage of a zener diode plug designed for 12 and 24 V systems. This means the XA2 DOUT takes the hit, the zener diode does not do any good. 

The XA2 will keep working for a while, but then it will break. 

The reason it works when you shift pins to a PWM output is that those drivers has not yet been burnt.. 

If you don't have plugs with regular diodes available, you can avoid damaging the module by using the XA2 COUT:s. 

The XA2 COUT and PWM out use the same pins, but in COUT mode there is an internal circulation diode that is connected to the load. In PWM mode, the XA2 disconnects this, which makes it becomes susceptible to damage when driving solenoid valves of this size.