Apologies, I have zero electronics skill or knowledge! I've been using my EMC2101 for a while and have it wired as the manual/PDF states [https://learn.adafruit.com/emc2101-fan- ... or/arduino], but today the RPM figures are now incorrect. So my question is, when using a 12v 4-pin PWM fan, how should I wire the TACH cable? Mainly because the TACH signal with be 12v?
Am I ok just to connect the grounds, as it is in the diagram, when using a 12v fan?
I'm still in the process of diagnosing, but need to now connect the FAN to a PC, while also using a different fan with the EMC2101 to see which is wrong.
EMC2101 - 12v 4-pin Noctua Fan
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- mikeysklar
- Posts: 13936
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Re: EMC2101 - 12v 4-pin Noctua Fan
There is an example non-invert op-amp circuit in this thread of another user who wanted to get a 12v fan going.
viewtopic.php?f=19&t=181894
viewtopic.php?f=19&t=181894
- Minxster
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Re: EMC2101 - 12v 4-pin Noctua Fan
Thanks for posting your reply. I did find that thread and tried to get my head around what it all meant. My fan is 4-pin and I'm able to control the speed with PWM since the PWM is 5v (??) with the EMC2101, which all seem ok. Its purely the RPM/TACH pin I want to read, but the thread you mentioned seems talk about fan control non-PWM with 12v?
- Minxster
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Re: EMC2101 - 12v 4-pin Noctua Fan
Just for clarity, what voltage fans is the EMC2101 compatible with? As I've been back over the detail on the main Adafruit site and it doesn't actually give this information?
- mikeysklar
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Re: EMC2101 - 12v 4-pin Noctua Fan
I think the documentation is intentionally open as to what voltage the fan can be.
For a 4-pin 12v fan setup I'd copy the example wiring as it quite explicit about the tach wire connection and connecting the DC power source (12v in your case) to the fan.
https://learn.adafruit.com/emc2101-fan- ... ng-3075968
For a 4-pin 12v fan setup I'd copy the example wiring as it quite explicit about the tach wire connection and connecting the DC power source (12v in your case) to the fan.
https://learn.adafruit.com/emc2101-fan- ... ng-3075968
- adafruit_support_bill
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Re: EMC2101 - 12v 4-pin Noctua Fan
On the fan the tach output is the open-collector output of a Hall sensor. If you look at the schematic for the EMC2101 board, the tach pin has a pullup to VCC (the VIN pin). So the tach signal voltage is the same as the voltage you apply to VIN. It doesn't matter what voltage is used to power the fan itself.
- Minxster
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- Joined: Mon Sep 20, 2021 8:51 am
Re: EMC2101 - 12v 4-pin Noctua Fan
That makes sense to me, I thought there was a clever (above my understanding) electronics thing it was doing :-)adafruit_support_bill wrote:On the fan the tach output is the open-collector output of a Hall sensor. If you look at the schematic for the EMC2101 board, the tach pin has a pullup to VCC (the VIN pin).
Thanks both of you for commenting back. I clearly know nothing about electronics, but I understand what you're saying, and indeed I've made sure the 12v supply, plus ground wires are connected as per the diagram. The TACH/RPM values I'm seeing are sometimes "ok" and other times just a load of rubbish (I don't think my 80mm fan is running at 65,000 RPM LOL). So knowing I've got it all wired correctly, I can start to track down my issue:mikeysklar wrote:I think the documentation is intentionally open as to what voltage the fan can be.
- FAN electrics issue
- PSU being noisy
- EMC2101 fault
Thanks both, for your help :-)
Please be positive and constructive with your questions and comments.