DMC Communication Problem : LUSENET : Elevator Problem Discussion : One Thread

I have a DMC that operates normally as long as our World Electronics Freedom Tool is plugged into it (the program does not need to be running)I have replace all the boards and the power supply (set at 5 volts), but have exactly the same problem.

The original problem was that the doors would open and close continuously (not trying to set up parameters) unless there was a call. When a call was made, the doors will close and the car take off. After takeoff, the car stops, hesitates, and continues on to the floor. Hook up the freedom tool, and the elevator operates normally...disconnect it, it reverts back to the original problem. The communication wiring looks ok.


-- Dan Redmond (, November 03, 2000


The Freedom tool works on a serial communication buss. Sometimes the wiring runs reflect signals back and forth or allow electrical noise pick-up if the wiring is not 'terminated' by an electrical load being attached. This causes communication errors and confusion back at the car controller transmitter/receiver. Does the installation of the cummunication cable have twisted pair shielded wiring? It should. Check to see that the car controller is grounded properly according to the manufacturers recommendations. Look for a broken or wrongly grounded wiring shield. If this doesn't solve the problem then look at the connection diagram of the signal wiring. Determine the signal wire pairs. Add a 1,000 ohm resistor across each signal pair. This might work best if the terminating resistors are placed at the end of the longest wire run away from the car controller.

-- Don Vollrath (, November 03, 2000.

Thanks... We found the problem

The problem was a bad capacitor on the 24 volt power suppy G-24 to P-24. This unfiltered power was apparently creating a noise problem. Since the Freedom tool has a built in filter to power the interface, it seems that it must have filtered the DC supply sufficiently to cause the system to operate normally. That is why the elevator operated normally only when the interface was plugged in.

-- Dan Redmond (, November 06, 2000.

Give Credit

I forgot to mention how helpfull the guys at World Electronics are. Their Freedom tool is great, and they provide great support.

-- Dan Redmond (, November 06, 2000.

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