What are these fan motors and what not to do ? - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: June 12, 2019, 10:02:10 pm
content: I want to use a 4pin intel i3/5/7 CPU cooler fan and it's.heatsink. Here's a few spec'shttps://www.superbiiz.com/detail.php?name=E97379They have +12Vin,GND, PWM and a sense pin. I want to drive it with some basic 555 circuit. Any idea what level voltage and current is meant to be feed to these, AC or DC ? IDK if there's active circuitry in these motors, IDK for sure what type they are. They're all pretty standard tho, because all CPU coolers are motherboard driven and work on any MB.Also they don't list zero rpm as the minimum speed, is that excluded for any real reason ? Maybe these fans are all digital, maybe I should use a common 12V fan and just PWM a driver FET or BJT

author: mariush
author_rank: Super Contributor
timestamp: June 12, 2019, 10:19:40 pm
content: It's standard 12v DC ... ATX standard says +/- 10% tolerance, so up to 13.2v DC should be tolerated.3rd wire is rpm sensor, two impulses for each rotation of fan4th wire is pwm signal ... it's standardized and in specification ... see the attached file.pwm can't turn off fan ... it's designed to work between 30% of maximum rpm or less (but minimum guaranteed to get fan working from full stop) and 100%.I'll quote it anywayThe following requirements are measured at the PWM (control) pin of the fan cable connector:PWM Frequency: Target frequency 25 kHz, acceptable operational range 21 kHz to 28 kHzMaximum voltage for logic low: VIL = 0.8 VAbsolute maximum current sourced: Imax = 5 mA (short circuit current)Absolute maximum voltage level: VMax = 5.25 V (open circuit voltage)Minimum Fan Speed RequirementsThe vendor shall specify the minimum RPM and the corresponding PWM duty cycle. Thisspecified minimum RPM shall be 30% of maximum RPM or less. The fan shall be able to startand run at this RPM. To allow a lower specified minimum RPM, it is acceptable to provide ahigher PWM duty cycle to the fan motor for a short period of time for startup conditions. Thispulse should not exceed 30% maximum RPM and should last no longer than 2 seconds. SeeFan Speed Response to PWM Control Input SignalThe PWM input shall be delivered to the fan through the control signal on Pin 4 (see Section 2.4).Fan speed response to this signal shall be a continuous and monotonic function of the duty cycleof the signal, from 100% to the minimum specified RPM. The fan RPM (as a percentage ofmaximum RPM) should match the PWM duty cycle within ±10%. If no control signal is presentthe fan shall operate at maximum RPM. See Figure 2.

author: lordvader88
author_rank: Frequent Contributor
timestamp: June 12, 2019, 10:33:01 pm
content: Excellent. If I had more LED displays and CD4026's, it would look really cool to have the fan RPM and loadtester temp, but that can wait for today anyways.Assuming CD4026 can be used to display a 2 or 3 digit temperature somehow, looking into that now, perhaps if it can only count, I'll make a V2F circuit.A loadtester should have a big temp display, or at least some LEDs driven with comparators, that would look cool, and an alarm and auto-shutdown