Welcome to the VizualDok - Here are some power aspects of Widex


All the cards are powered by 48 Volts DC from the backplane. This voltage is equilibrated to be +24V and -24V from ground. Every card contains its own DC to DC converters to satisfy its own needs.Every card has a fuse and a reverse diode protection.


The power comes from two  1 kW cartridges that share the load. For 15 baselines, the consumption is low so that one alone can be standing the load and the other  might be dead unnoticed. Inspect the "DC OK" green LEDs  from time to time to avoid this situation.

The power dissipation of every unit largely depends on  the task it is performing.
In powersave mode the power is approximately 200Watts.
At power-up (with no software initialization), the power is 650Watts
At normal work (8 antennas, cross corr) it reaches 1.15 kW . With no cooling it would auto-destroy in less than 3 minutes.
There are two safety circuits which try to avoid this unpleasant issue,one causes recoverable standby and the other causes total shutdown.



1. Standby circuit 

All correlator cards have a thermometer (U38) located at the top. Only cards #4 and  #12 are read out, giving temp_Left and temp_Right , respectively (named from front view).   If one of the two temperatures exceeds 60C, the FPGA stops the 250MHz system clock, causing the power to drop to 200 Watts. This allows the system to cool down until it reaches 43C where it restores  the clock automatically. During this period the software is not hooked up and can continue reading the data (which  of course is wrong).This situation is signalled by the "overheat" status bit on.





IF the cooling is not sufficient,  the system would cycle indefinitely with a period of  ~8 minutes .






2. Shutdown circuit 

The airflow  cools down a thermistance that  heats up when the flow is interrupted. After a limit set by the front potentiometer the power supply is stopped automatically and has to be restarted manually.







Under normal conditions the yellow LED is on. The red button overrides the safety circuit.  To set the limit, keep it pressed  and  manoeuver the potentiometer while observing the  yellow LED. Full left is no safety at all. Turn right gently until the LED stops, then turn back to have some margin. You can relase the red button.



Try it by stopping the blower (by removing  the jack) . The unit must stop within less than 30 seconds.  Never override the safety circuit for more than one minute without cooling ( unless you absolutely want to destroy the unit)





At sea level the measured cooling parameters are as follows:
Exhaust airspeed : 13 km/h
Airflow  210 m3/h
Input power  48V, 23.4 A  (1.12 kW)
Air temperature increase  15.0C  (13.4 C/kW)




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