Live sound engineering is facing its biggest change ever during the winter 2012...13. Transition from tubes to transistors or from analog to digital was just natural evolution.

The way we do live mixing will be totally different than a year ago. The sound system will be controlled with personal mobile gadgets.

Naturally it was Mackie who made affordable equipment available for iPad based live mixing. I am a one man R&D team. I try to develop simple DIY solutions with a vision similar to Greg's.

Monday, August 13, 2012

More current measurements

When measuring the fader motor current, I noticed that the current value drops quite rapidly. That is because of motor winding temperature rise. In loudspeakers that is called power compression.

I made another current measurement iteration. This time waiting some ten minutes for each voltage step and see where the current value sets.


4    210   190    24
5    260   230    30
6    310   265    37
7    360   300    43
8    410   330    50
9    460   350    61
10    510   370    70

Columns:
  1. Voltage / V
  2. Current cold / mA
  3. Current hot / mA 
  4. Calculated temperature rise / C 
Assuming that the motor has copper winding, we can calculate the temperature rise from electric current value shift. Temperature coefficient of copper is 0.0039/C (Aluminium is the same).

We could accept the temperature rise of 70 degrees Celsius with 10 volts in room temperature. That would make 95 C degree in 25 C room temperature but professional equipment must be designed for extreme violent conditions. Direct sunlight may cause some 50 C degree ambient temperature.

9 volts and 50 C ambient temperature would mean 111 C winding temperature. That is absolute maximum in extreme conditions. That is fully acceptable.

Motor windings can take temperatures above 150 C but there are other parts inside the motor made from unknown materials. Anyway the cooler, the longer life.


Hey com'on

We are not going to write a software  that keeps the motor pulling at full force for hours. No, we are not, but we are professionals and we have to consider extreme conditions and situations that can be caused by a malfunctioning component, in hardware or software.


Conclusion

We can keep keep the previous voltage plan and feel safe.

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