Author Topic: MC090-020 "searchlight" and "Startup" inputs?  (Read 2689 times)

Offline oiltronic

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MC090-020 "searchlight" and "Startup" inputs?
« on: April 14, 2015, 07:36:38 AM »
Where can I find an explanation of the "searchlight" (or "PWMLight") digital inputs of the MC090-020, that are somehow fed a common internal PWM signal?  I was surprised to find that the datasheet mentions nothing about these special digital inputs that have neither pull-up or pull-down config settings in GUIDE.   The controller family tech info and input config tech note mention nothing.  And the API says very close to nothing.  Is there a document I missed somewhere?  Can someone enlighten me on how these pins work?

Offline oiltronic

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Re: MC090-020 "searchlight" and "Startup" inputs?
« Reply #1 on: May 08, 2015, 02:44:20 AM »
Here's what I learned about the MC090-020 from some helpful people at Danfoss:
  • It was originally a custom design for a particular European customer, and Danfoss felt it was useful and unique enough to put on the market.
  • You need to thoroughly read the datasheet, read the API spec, and explore the input & output settings in software before selecting this controller model or designing your circuit.  I suppose this applies to all Plus+1 controller, but this one especially.
  • Pins C1-P1,2,10-25 are a block of digital inputs with the "searchlight" or "PWMLight" function.  These are in fact simultaneous inputs and outputs.  They are primarily digital inputs in that the input voltage is sampled at the low end of a common PWM output on the same pin.  The PWM output on these pins is an adjustable 0-80% fixed-frequency open-loop voltage used to power things like LED indicators on all operator switches that are tied to these inputs.  The only software setting for the PWMLight level is applied to all these digital inputs at once.  So if you set the PWMLight level to say 50%, the LED's on the switches will be dimly lit, then when the switch is pressed and connected to supply voltage the light will go brighter.  Pretty neat.
  • All the above digital inputs have an internal fixed 2.7k pull-down resistance.
  • The digital output pins C2-P1-23,30-35 all can detect whether something is connected when the load is off.  (Most output pins in the Plus+1 microcontroller family only detect a load when the pin is turned on, by measuring the current.)  These MC090-020 pins detect a load when the pin is off by leaking out up to 5.8 mA (yes, mA) and measuring what's happening at the pin.  So you can only use these outputs for loads that require much more than 5.8mA to switch on such as solenoids valves, large relays, etc.  Not for LED indicators, low-power relays, etc.