Sanity check - usb device on 4-pin molex

Habakkuk

Habakkuk

Habakkuk

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Before I risk hooking it up, the 4-pin molex from a PSU has a 5V supply and a ground - can I use an adaptor to run a usb device?

I'm trying to hook up a raspberry pi zero to control lights/fans in a computer case without usb sockets or motherboard usb headers available - only the power supply is needed for usb, not the data pins.
 
Yes that will work, should be quite a clean 5V supply. Make sure you wire up the 5V and not the 12V! I'm assuming this will only drive the Pi in terms of power, but its load (lights and fans) will have their main supply come from the PSU directly? So we're talking up to 1A of the PSU's capacity.

If you have any noise issues on the power rail, you should be able to mitigate it with filtering capacitors. But don't worry about it unless you run into problems.

Make sure you wire it safely and use common sense!
 
Right - wired up, the 12V molex adapter works fine for the rgb lights - but the 5v adaptor isn't booting :/

On the bright side, it still works under regular usb power, so I've not fried it.
 
Habakkuk said:
Right - wired up, the 12V molex adapter works fine for the rgb lights - but the 5v adaptor isn't booting :/

On the bright side, it still works under regular usb power, so I've not fried it.
Click to expand...

How are you connecting it? The Pi can be powered via micro USB or applying 5V and ground at its GPIO pins. Worth a try?
 
Oh of course, the Zero doesn't have header pins fitted at stock. I'm guessing the issue is somewhere in the micro USB cable/connector but tricky to diagnose as it's tiny.
 
Do you have a multimeter or anything to make sure you are actually getting 5V from the connections you are using?
 
Yeah, I'm going to have to break out the Fluke multimeter for this - and it's the right socket.

It's powering up, just not loading from the microsd.
 
Habakkuk said:
Yeah, I'm going to have to break out the Fluke multimeter for this - and it's the right socket.

It's powering up, just not loading from the microsd.
Click to expand...
Oh - I had this issue and sent my Pi back thinking it was broken. Turns out getting an SD to boot is finicky, and sometimes they just die too. Is it still booting plugged into a normal usb cable outside the pc? Make sure it can deliver enough current.
 
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