12v/3 amp DC fan - ground?
June 21, 2024 4:24 AM Subscribe
My bug vaccuum is puny. I got this fan to make a better one. I have a 12v power pack and will check the amperage it supports. The fan has three wires to connect; one of them is ground. I read something about connecting the "ground" wire to the chassis? What?
...Especially if my chasses isn't metal, what should I do here? Anyone?
...Especially if my chasses isn't metal, what should I do here? Anyone?
I think that model is PWM controlled. Red to the positive, black to the negative of your power supply. I think the 3rd wire is the pwm lead, if I had to guess, I would think that it needs to be tied "high" (to the positive supply) but you could just leave it floating and see what happens.
posted by Larry David Syndrome at 6:57 AM on June 21 [1 favorite]
posted by Larry David Syndrome at 6:57 AM on June 21 [1 favorite]
“the 3rd wire is the pwm lead”
From the picture there appear to be four leads. I’m thinking one of the extra two is PWM, but I don’t know about the other.
I could be convinced that there’s only three leads there though.
posted by Tell Me No Lies at 7:16 AM on June 21
From the picture there appear to be four leads. I’m thinking one of the extra two is PWM, but I don’t know about the other.
I could be convinced that there’s only three leads there though.
posted by Tell Me No Lies at 7:16 AM on June 21
The OP says 3 wires. If there is a 4th wire it could be a tach sensor lead to feed back what RPM the fan is spinning to the controller (if any) I'll take a closer look later when I'm not on mobile.
posted by Larry David Syndrome at 8:19 AM on June 21 [1 favorite]
posted by Larry David Syndrome at 8:19 AM on June 21 [1 favorite]
I checked the manual, it's a four wire fan. It will run at 100% with nothing connected to the PWM input.
So only red + and black - and it will run.
posted by samj at 8:31 AM on June 21
So only red + and black - and it will run.
posted by samj at 8:31 AM on June 21
Response by poster: Thanks for the responses so far.
- I have the fan already, and it has three wires.
- red (+ apparently), yellow (- ?), and black
- The instructions here say, on page 2 under "DC fan and blowers,":
- I have the fan already, and it has three wires.
- red (+ apparently), yellow (- ?), and black
- The instructions here say, on page 2 under "DC fan and blowers,":
The lead wire from the fan unit is connected to the DC power supply with specified voltage. The red wire is +, and the black or blue wire is - (GND) in principalposted by amtho at 10:24 AM on June 21
Response by poster: Oh no. I linked the wrong one. Why do they look so alike?
It's actually model 9g0912g010 - looking at that page now.
posted by amtho at 10:30 AM on June 21
It's actually model 9g0912g010 - looking at that page now.
posted by amtho at 10:30 AM on June 21
Response by poster: "The red wire is +, and the black or blue wire is - (GND) in
principal."
I mean, I truly would have figured that out when it was time to solder - I forgive myself for linking to the wrong page because that's not really the information I need.
My question is really: if there *is* a GND wire (and there is), what do I do with it?
posted by amtho at 10:33 AM on June 21
principal."
I mean, I truly would have figured that out when it was time to solder - I forgive myself for linking to the wrong page because that's not really the information I need.
My question is really: if there *is* a GND wire (and there is), what do I do with it?
posted by amtho at 10:33 AM on June 21
In a DC setup, as it is here, 0V and GND can be interchangeably used depending on the whim of the writer of the manual, the fluid level of their vessel of work fuel, the phase of the moon and a few other measurable as well as random parameters.
A GND reference does not require that part of a DC circuit to be connected to mains ground, unless there's a specific reference in the manual/assembly instructions that you should.
About the third and fourth wire: yellow is tach, purple is PWM.
posted by Stoneshop at 10:50 AM on June 21
A GND reference does not require that part of a DC circuit to be connected to mains ground, unless there's a specific reference in the manual/assembly instructions that you should.
About the third and fourth wire: yellow is tach, purple is PWM.
posted by Stoneshop at 10:50 AM on June 21
Black/-/GND is the power return line, it doesn't necessarily need to be connected to an actually earth ground. It needs to be connected to the - side on the power supply to complete the circuit.
posted by Teadog at 10:57 AM on June 21
posted by Teadog at 10:57 AM on June 21
Response by poster: Right - I should have noticed that.
Apparently the yellow (third and final) is for a sensor. Fine.
And that's how you gradually learn how to order parts from DigiKey: experience!
posted by amtho at 11:04 AM on June 21 [1 favorite]
Apparently the yellow (third and final) is for a sensor. Fine.
And that's how you gradually learn how to order parts from DigiKey: experience!
posted by amtho at 11:04 AM on June 21 [1 favorite]
To touch on your deeper question, there is absolutely such a thing as a chassis/earth ground which is really just there to make sure *you* don't become the ground point through which the current runs. That's the third prong on any of your standard outlets that have them. As you've seen here, you aren't dealing with that in this particular case, but yeah anytime you have something specifically called out as needing to go to a chassis ground, you absolutely should do that, and the component that it's hooked to needs to be properly grounded as well.
posted by Teadog at 1:27 PM on June 21
posted by Teadog at 1:27 PM on June 21
Response by poster: Thanks, Teadog. What if the item is a small, hand-held, battery-operated fan? With a non-metal body?
This fan is about 1.1 amps, but I might try a 12 volt, 3 amp version if this isn't powerful enough (it only has to work in 2-5 second spurts). In that case, might "grounding" be more important, and necessary practices change?
posted by amtho at 4:15 PM on June 21
This fan is about 1.1 amps, but I might try a 12 volt, 3 amp version if this isn't powerful enough (it only has to work in 2-5 second spurts). In that case, might "grounding" be more important, and necessary practices change?
posted by amtho at 4:15 PM on June 21
Response by poster: Thanks, Teadog. What if the item is a small, hand-held, battery-operated fan? With a non-metal body?
Things that aren't mains-powered when in use don't need a ground. Not even a portable flowerpot with a wire between your device and the soil in the pot. With such a device, GND is just the return circuit to the [-] pole of the battery.
posted by Stoneshop at 4:12 AM on June 22
Things that aren't mains-powered when in use don't need a ground. Not even a portable flowerpot with a wire between your device and the soil in the pot. With such a device, GND is just the return circuit to the [-] pole of the battery.
posted by Stoneshop at 4:12 AM on June 22
And whether such a battery-powered device has a metal body or exposed metal parts doesn't make any difference. Grounding a device by connecting it to mains ground only matters if the device is mains-powered. If the device is powered by a wall-wart or an external adapter (e.g. laptops and tablets) it doesn't need to be grounded either; if it needs to be it will come with a specific power brick that provides the grounding.
(apparently something just changed on MF, the 3-minute window to edit a reply is gone)
posted by Stoneshop at 4:24 AM on June 22
(apparently something just changed on MF, the 3-minute window to edit a reply is gone)
posted by Stoneshop at 4:24 AM on June 22
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posted by Tell Me No Lies at 5:58 AM on June 21