Author Topic: How can I switch on a high-current device with a CMOS switch or similar?  (Read 842 times)

0 Members and 1 Guest are viewing this topic.

Offline MarmottaTopic starter

  • Contributor
  • Posts: 37
  • Country: gb
I'm building a PC using an Intel NUC motherboard and an external graphics card - both will run off 12V, but when the motherboard is in standby, the graphics card fan with run at full speed, as the 12V will always run to it as long as the power supply is connected to the mains.

Ideally I'd want a positive voltage from the motherboard (between 3-5V or so) sent to a circuit that will then relay the 12V to the graphics card when the motherboard is powered on. I know CMOS switches can perform similar tasks in low current scenarios, but the graphics card can pull 75W, so the current would be around 6.25A, far higher than anything I've seen. Any ideas on how to get around this? I think there might be a pre-built solution out there already specifically for small factor PC builds, but as I need to make a custom PCB for parts of it anyway, I'd rather just stick my in circuit on it as well.
 

Online ledtester

  • Super Contributor
  • ***
  • Posts: 3282
  • Country: us
Re: How can I switch on a high-current device with a CMOS switch or similar?
« Reply #1 on: September 06, 2019, 08:34:58 pm »
Ideally I'd want a positive voltage from the motherboard (between 3-5V or so) sent to a circuit that will then relay the 12V to the graphics card when the motherboard is powered on.

How about using a 5V relay? Relays like this are good for 10A:

https://www.amazon.com/Tolako-Arduino-Indicator-Channel-Official/dp/B00VRUAHLE/ref=asc_df_B00VRUAHLE/

Alternatively hook up your fan to temperature controlled fan controller so it only runs when it's hot, like this one:

https://www.ebay.com/itm/12V-PWM-Fan-Temperature-Speed-Controller-Module-High-Temp-Alarm-5V-Buzzer-PC-CPU/263605466941
 

Online mariush

  • Super Contributor
  • ***
  • Posts: 5171
  • Country: ro
  • .
Re: How can I switch on a high-current device with a CMOS switch or similar?
« Reply #2 on: September 06, 2019, 08:56:20 pm »
Check your video card, it may have a 4 pin fan connector, which means the video card's firmware may be able to dynamically adjust the fan speed based on heatsink temperature.

Alternatively, you can buy a fan controller and glue the NTC (temperature sensor tip) to the heatsink, then optionally configure the min and max temperatures : https://www.ebay.com/itm/PWM-4-Wires-Fan-Temperature-Controller-Speed-Governor-DC-12V-for-PC-Fan-Alarm/372494614639?epid=24023606409&hash=item56ba68c06f:g:yBYAAOSw1cdb4qmd

There's instructions attached to the ebay listing above, it's fairly easy to use once you understand the instructions
 

Offline MarmottaTopic starter

  • Contributor
  • Posts: 37
  • Country: gb
Re: How can I switch on a high-current device with a CMOS switch or similar?
« Reply #3 on: September 06, 2019, 09:07:10 pm »
Ah, yes, a relay should do the trick nicely, thanks.

As for the fan, it's a non-issue if I can regulate the 12V power going to the graphics card. When the motherboard is turned on, I can regulate the fan speed via software.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf