Start-up and shut-down voltage
This chapter should be read with caution and attention as long as the fans are not purely analog, i.e. DC-controlled with 3-pin connector. The PWM control electronics almost always stand in the way of clean voltage regulation and it is also therefore not advisable to regulate PWM fans via voltage. Nevertheless, we also performed this measurement for all models, regardless of whether they are DC or PWM fans, because even strange results say a lot about the control electronics and the use as a DC-controlled fan.
First, however, we check the maximum speed at 100% PWM to be on the safe side and compare it with the data sheet. The fan manages the specified data and is even slightly above it after the 24-hour run-in. Of course, there is usually also a smaller series dispersion involved, so that already fits.
In today’s DC test, we see that the fan already starts with voltages starting at about 3.7 volts. The cutoff voltage is 3.1 volts, whereby the technically possible around 250 rpm slightly differs from the measured 740 rpm. And it also doesn’t start up again until 795 rpm. Thus, the fan is not suitable for real DC control because you cannot regulate it down far enough.
The PWM-controlled start-up speed is 326 rpm, and the PWM-controlled fan only stops at 271 rpm. The fan does not quite meet the specs, but it almost does.
Start-up and shut-down behavior
The following measurement curves once again illustrate the very different behavior. Let’s look at DC control first. Here, the new fan requires 600 rpm as the starting speed, and a standstill already occurs below 500 rpm. This is rather worthless as a control range and makes these fans somehow useless as pure DC fans (see above).
With the PWM protocol, we can also see very well the progression up to the minimum speed, which then leads to the desired standstill.
Power consumption
This value of open operation as a case fan is pleasantly low, especially at low speeds. However, you should also consider that four fans together would only consume the roughly 12 watts that a header can supply at full load. From this point of view, a common DC control of all installed fans of a system via a single 1-A header would not be impossible, but would still be pointless due to the control ranges. But rather PWM, which regulates better.
However, power consumption is not the same as power consumption, because it fluctuates quite a bit between radiator operation and free installation as case fan! This graph is also new and should help in assessing the system load, as the power consumption increases to just under 3.4 watts on the radiators at maximum. And that only in the peaks, free in the case it is rather 3.1 watts.
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