Tom,

We have lost input function on 3 different Konnect boards, and here is how we have it set up:

Hi Scott,

Sorry to hear you are having trouble.

Strange as the circuit should have lots of margin to run at 24V.

Your statement "switch is connected to -24 ground" is a bit confusing.  Is it connected to -24V?  That would apply 48V to the circuit and would likely cause damage.  I assume you mean the GND terminal of the +24V supply?   Where is your voltage analyzer connected exactly?

The input circuit is simply a 4K ohm 1/4watt resistor, the visual LED, and the Opto LED in series.  This should result in ~5ma of current at 24V.  The two LEDs are rated at 30ma continuous.  The 4K om resistor should dissipate 0.1Watt (less than its 0.25Watt rating).  You might check the resistors near the LEDs to see if they are actually 4K ohms and if they are different after the channel has been damaged.

I wouldn't expect a narrow voltage spike to cause damage.  But you might consider using a separate isolated supply from the valves and relay coil outputs.

You could add series 4Kohm resistors to your switches.  This would reduce the voltage that the Konnect Circuit sees to ~12V.  Putting a resistor in series with the Common connection wouldn't be a good idea.  Another option would be to simply use a 12V supply.

Regards

TK

 

Tom,

We have lost input function on 3 different Konnect boards, and here is how we have it set up:

•  +24V on input bank commons
  
• 7 normally opened switches connected to input
  
• The other side of the switch is connected to -24 ground
  

The input we are loosing is connected to switch that is constantly on. It works fine for a few hours and then stops working. The digital input screen doesnt show any change when the switch is toggled. If you look at the LED on the Konnect it comes on very dimly. So dim you can hardly see it - a jumper directly to ground has the same outcome. 

When I change the input the switch is connected to it starts working again, for a while, until that input burns out to. This has happened on 3 boards with 2-4 inputs burning out on each Konnect. We hooked a voltage analyzer to the 24V supply and tracked it today - we lost two inputs. The voltage varies quite a bit as we have 4 valves, a Keyence imaging camera, lights, relays, and many sensors on the same circuit. The high was 23.1 volts and the low was 21 volts. 

The manual says the Konnect should handle 25 volts. Do you have any idea why we could be loosing these inputs? Maybe we are getting a voltage spike not being picked up on our meter from one of the relay coils? Perhaps we are running on the high end of the optocoupler? We are getting a bit desperate to get our equipment running again. Burning through boards pretty quickly. Maybe add a resistor to the input bank commons to drop our voltage down to the 5V range??

Any suggestions you have would be very helpful. We are really struggling at the moment.

Thanks,

Scott