UPS with silent fans - Page 1
Forum section: electronics / beginners

author: TheGenesis
author_rank: Contributor
timestamp: September 08, 2021, 10:40:12 pm
content: Hey folks,someone donated me a 6000 KVa UPS (XANTO XSRT6000) and i want to power some pc's in my home office with this thing.Unfortunately the fans are very load and I need to bring these decibels down.My first attempt was to replace the stock fans with some quiet pc case fans.The temps are fine, but the thing refuses to load the batteries because of a constant fan error.These are the stock fans:https://www.mouser.de/ProductDetail/Sanyo-Denki/9G1212E1D011?qs=noSWugIXIHrca0mLXh7GKw%3D%3Dand these are the ones i tried to replace them with:https://www.performance-pcs.com/fans-accessories/120mm-fans/noiseblocker-nb-eloop-b12-4-120mm-x-25mm-ultra-silent-bionic-blade-fan-2400-rpm-34-29-dba-nb-eloop-b12-4.htmlAs the rpm's of the new fans are lower i have addedthisRPM-Simulator and set it to round about 3200 rpm but the error will not vanish until i reconnect the stock fans.Does anyone know a trick to fool the ups of thinking the original fan is installed?Thanks in advanceThomas

author: james_s
author_rank: Super Contributor
timestamp: September 08, 2021, 10:48:45 pm
content: Use an oscilloscope to look at the signal produced by the original fans and program a microcontroller to duplicate it. Does the UPS actively control the speed of the fans or just monitor that they're all running the correct speed? What about just putting the whole UPS in a closet and run a cord to the loads?

author: TheGenesis
author_rank: Contributor
timestamp: September 08, 2021, 10:56:43 pm
content: I think the ups performs a sanity check at startup and measuring speed while ramping up the fans. Your suggestion with the microcontroller is far beyond my scope. I was already happy successfully replicating the little rpm simulator

author: KaneTW
author_rank: Frequent Contributor
timestamp: September 08, 2021, 11:14:05 pm
content: Probe the sensor line on the Sanyo fans. Check how to drive it. Then you can work from there.

author: james_s
author_rank: Super Contributor
timestamp: September 09, 2021, 03:45:46 am
content: You might find a quieter fan that produces the same signal. Careful not to compromise the airflow though, make sure you test it at full load as the battery voltage nears the lowest level before it shuts down, that's when the current will be the highest and the inverter will produce the most heat.

author: Jeroen3
author_rank: Super Contributor
timestamp: September 09, 2021, 05:41:46 am
content: Check the circuitry around the fan header and see if there is a current measurement circuit.Also, if the UPS attempts to adjust the fan speed, that may also cause it.

author: nexus
author_rank: Regular Contributor
timestamp: September 11, 2021, 02:29:18 am
content: most fans, both 3 wire (no speed control), and 4 wire (PWM speed control) use an open collector circuit for a tachometer. Each revolution equals two low pulses.https://www.petervis.com/electronics%20guides/cpu%20fan%20tacho/cpu%20fan%20tacho.htmlThe voltage level is typically 5 volts (TTL). Try measuring the fan connectors on the UPS with no fan connected using a regular DMM. What is the voltage across ground and the tachometer pin?Make sure your tachometer simulator is operating at the same logic level (voltage level) and is producing a 50% duty cycle square wave at approximately double the RPS of the original fan (if original fan spins at 3200rpm, 3200 rpm is about 53 revolutions/second. 53 x 2 = 106 hz).Also, make sure your tachometer simulator is grounded properly. It needs to be ground referenced to the fan's power ground. I.E. make sure you don't have a "one wire circuit".Posting pics would also be good to help us help you.

author: TheGenesis
author_rank: Contributor
timestamp: September 11, 2021, 12:05:03 pm
content: Thanks for all the suggestions.The tachometer pin (yellow wire) is 5V and my tachometer simulator is properly grounded. I modified a 555-timer ciruit for led's from amazon and tested/adjusted it on my test pc.There is no obvious current measurement circuit around the fan header. You mean a shunt resitor, right?I have tried 3 different fan's and none of them worked.Yesterday i placed the ups in basement and after i integrated it into my breaker box i accidentally dropped the battery pack which brake three batteries. Now i have to look for some used batteries to match the others.

author: nexus
author_rank: Regular Contributor
timestamp: September 11, 2021, 04:00:57 pm
content: If your tachometer simulator is at the right logic level and grounded, then perhaps the only other issue I could think of with that circuit is that it does not have enough pull to bring the tach signal down to a "low" logic level (at least below 2.5 volts). Do you have a scope to probe between pwm and ground to see what the signal looks like here?An quick alternative circuit would be to use an arduino to drive a transistor with PWM, to simulate the fan tachometer pulling down the tachometer line 2 times per revolution.If the UPS is doing some kind of current or alternate speed sensing method (increasing and decreasing speed), you might be better off just disabling the alarm if that is the problem.Does the UPS have any kind of usb or interface that let's you configure operation or view diagnostics? Maybe it has some PC software interface that works over USB/ethernet?

author: TheGenesis
author_rank: Contributor
timestamp: September 24, 2021, 05:31:25 pm
content: Unfortunately there is no hack for the settings available. The guys from the manufacturer support are not allowed to give any assistance to such a topic.So i take the advice and moved the thing into my basement and wired it to my office supply.This is a total win for me because it's constantly 25°C there and no noise is escaping to the basement.

author: james_s
author_rank: Super Contributor
timestamp: September 24, 2021, 07:40:33 pm
content: I think that's a much better long term solution anyway. It's taking up less valuable space, it stays cool which will be appreciated by the batteries especially, and you don't have to mess with modifying the hardware. You should put a smoke detector down there if there isn't already though.