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Precision X1 output correct PWM signal with no Tachometer signal

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B0baganoosh
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2021/08/23 11:41:35 (permalink)
Short of soldering up a jumper cable, is there a way to get Precision X1 to properly output the right PWM signal even if it can't read a tach signal?
 
Background:
I currently have a hybrid kit on my 3080 ti and there are 4 fans I'd like to control for the radiator, so I have them going through a fan hub. The hub's control cable (4-pin) goes back to the hybrid kit's "fan 1" splitter cable that normally goes to the rad-fans, but I have different fans with different RPM ranges, so I just want PX1 to output the duty cycle to the fan hub based on temperature. When I hook it all up, PX1 says what % it should be driving based on the current temperature, but the fans run at 100% the whole time. While in BIOS (pre-windows), the fans run at a lower speed, so it seems that it is PX1 setting the fan speed at max. I also tried to not use a curve and just use the sliders to fix a %, but it didn't work. If I plug the hub into my motherboard and set a fixed speed (65% for example), it does that perfectly fine, but I can't use GPU temp from my motherboard's fan header.
 
My current plan is to make a splitter cable that passes all lines from one of the EVGA rad-fans to the hub, but splits the tach-line off to a separate fan plug. Then I'll plug the fan hub's plug into the GPU's splitter cable that doesn't have the tach line and the tach-cable over to the splitter cable that does have the tach line. Rudimentary sketch:
 
Is there a way to get PX1 to drive the fans correctly without adding the DIY tach-splitter cable?
 
post edited by B0baganoosh - 2021/08/23 11:43:22

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i9 11900k - EVGA Z590 FTW - EVGA RTX 3080 ti FTW3 Ultra (+Hybrid Kit) - 32GB 3733MHz CAS16 G.Skill, gear1 - WD SN850 2TB NVMe Gen4 - BeQuiet! Dark Base 900 Pro. Project Dark Water MODS RIGS post for build notes.
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    B0baganoosh
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    Re: Precision X1 output correct PWM signal with no Tachometer signal 2021/08/24 12:20:50 (permalink)
    I was just thinking about this and realized that while it would put some fan load back on the card (which isn't really a big deal), I could just do this, drawing in additional fans for clarity:

    Then it would have the tach signal from the first fan and the other three could run off the hub getting the same PWM signal from the hybrid kit's splitter cable.
     
    Jacob suggested I try the GPU's aux-fan header from the hub. I might try that too, but I'm not sure the hub's input cable will reach that header as it is designed to go direct to a motherboard fan-header. That would keep all the fans' power load off the GPU though, as the hub is powered by a SATA Power cable.

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    Formerly Nike_7688 (please refer to post#77 here for info)

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    B0baganoosh
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    Re: Precision X1 output correct PWM signal with no Tachometer signal 2021/08/24 19:06:48 (permalink)
    I tried both options and the second one seemed to mostly work, but it was a bit intermittent. Seemed like the hub fans would sit at lowest speed and not change. I wiggled the connector and they started following along with the fan directly plugged in. I thought "oh good it's working", put my side panel back on, and it stopped working.

    Also, plugged in to aux fan connector on the gpu before trying my second sketch above and that did the same thing as before, full speed fans. I have read that it should have showed up as "fan 4", but no fan 4 showed up in px1, even after rebooting the computer. Does px1 need to be reinstalled to get this to work or could it actually just be a loose connection between the hub connector and two different fan headers? It always works fine when plugged into a motherboard header, so I'm not sure why it would be acting so weird on either gpu fan header.

    I know the hub connector doesn't feed back a tach signal, so I'm guessing that would make the gpu not see that there's a "fan 4" connected, but I am only guessing. I came up with one other idea that doesn't require custom cables, but it will only work based on the specific way I've hooked my fans up (see mods rigs section post in signature lol). I can just run the evga fans on the "fan 1" splitter cable and the other two fans (which are quieter) on a different constant signal not controlled by px1. Not ideal, but it should be tolerable and still better than just running all the fans at ~65% forever regardless of load.

    Formerly Nike_7688 (please refer to post#77 here for info)

    i9 11900k - EVGA Z590 FTW - EVGA RTX 3080 ti FTW3 Ultra (+Hybrid Kit) - 32GB 3733MHz CAS16 G.Skill, gear1 - WD SN850 2TB NVMe Gen4 - BeQuiet! Dark Base 900 Pro. Project Dark Water MODS RIGS post for build notes.
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    B0baganoosh
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    Re: Precision X1 output correct PWM signal with no Tachometer signal 2021/08/25 17:12:35 (permalink)
    Update: I left it plugged in per the second drawing above. Today it booted up and the fans all ran correctly. Also, to throw another wrinkle in that I accidentally left out: the two "other fans" are 3-pin fans. The hub has outputs for both (different connectors, driven separately, not an either/or setup), so as long as it gets the pwm input signal, it will drive all the connected fans to that % or full, whether pwm or voltage controled. That's why I can't just get one of those splitters with a molex built in. Here's what my hub looks like:

    post edited by B0baganoosh - 2021/08/26 08:03:52

    Formerly Nike_7688 (please refer to post#77 here for info)

    i9 11900k - EVGA Z590 FTW - EVGA RTX 3080 ti FTW3 Ultra (+Hybrid Kit) - 32GB 3733MHz CAS16 G.Skill, gear1 - WD SN850 2TB NVMe Gen4 - BeQuiet! Dark Base 900 Pro. Project Dark Water MODS RIGS post for build notes.
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