Understanding small voltage regulaters - constant 12V DC output - variable DC input

[Yoda]

Yep I am out of my corner again. In researching my fridge fan project I am running up against a voltage issue. Its probably not a real issue as I have been told, but I would like to learn about theses regulators and if one is prudent to use. Computer fans are mostly rated 5v - 12V. Anything above that may shorten thier life, and as one manufacturer mentioned void warranty (standard cover thier hiney)

So I need electrical advice beyond what little I know. Here is the situation. When My batterys charge they can see 14.4 volts at times which means the trailer DC wiring will also see 14.4V. So the fans will see that voltage too. I think I may need a simple voltage regulator that delivers constant 12V dc OUT with variable DC voltage in. Something simple.

This is what I found, but have no idea which is the correct choice. Some are adjustable, others preset.

https://www.amazon.com/dp/B09H264Z61..._rd_w=mz6u3&am

https://www.amazon.com/DROK-Converte...8743736&hv

https://www.amazon.com/Voltage-Stabi...8550635&hv

https://www.amazon.com/DROK-Waterpro...ds=dc%2Bvoltag

So can an electronics wizard help me choose wisely, if I do need constant 12V for theses fans? All the fans I am looking at draw less than 1.3 amp (max start up) each. So for a pair the regulator might see say 3 amps. My current fan choice is less that 1 amp total per pair. While it may seem petty I am paying attention to power usage. One other thing is I plan to use a speed controller so I can vary the speed needed or just have them off if fridge is doing good. And I have no idea how sensitive PWM speed controllers are to voltage.

Thanks for any help
Keith

[TedS]

Make your own. Vary the voltage to vary the fan speed.
https://www.youtube.com/watch?v=uXjX3S1Ohoo

[colan]

I’m a long way from being an expert but… I don’t think it is something to worry about in regards to 12v items. The reason for thinking it doesn’t matter is all of the DC 12v stuff in the RV lives just fine on nominal 12v ranging from sub 12 to over 14 volts.

On the other hand running 5v things at 12v probably isn’t a great idea.

[Yoda]

I’m a long way from being an expert but… I don’t think it is something to worry about in regards to 12v items. The reason for thinking it doesn’t matter is all of the DC 12v stuff in the RV lives just fine on nominal 12v ranging from sub 12 to over 14 volts.

On the other hand running 5v things at 12v probably isn’t a great idea.

Thanks Colan
The fans are rated 12V but can operate as low a 5V - I think the are made that way as different computers control fan speeds different ways. I think it has to do if the wiring is 2,3, or 4 wires called out in numbered pin connectors. And I could be very wrong on this information too.

In normal situations they are plugged into the mother board that does the thinking. In my case I want to install stand alone and use a manual speed control like this. https://noctua.at/en/products/accessories/na-fc1 https://www.amazon.com/dp/B072M2HKSN?tag=noctua0b-20 The problem is information is lacking on voltage limitations. I guess I just need to send out a few more emails.

Thanks
Keith

[Dnmatt]

This is the one I've been using for a couple of years with no problem. If you look at the question section the manufacturer has said they've tested up to 24V.

Coolerguys 120mm (120X120X38) High Airflow Waterproof IP67 12v Fan https://www.amazon.com/dp/B07P46D62Q...ing=UTF8&psc=1

[Yoda]

This is the one I've been using for a couple of years with no problem. If you look at the question section the manufacturer has said they've tested up to 24V.

Coolerguys 120mm (120X120X38) High Airflow Waterproof IP67 12v Fan https://www.amazon.com/dp/B07P46D62Q...ing=UTF8&psc=1

I emailed them about that fan and the said over 12V shortens the fan life and they don't recommend it.. Their 3 pin fan controller also cant handle the high amp draw. Its good to know its working for you. How noisy is it and how do you have it wired if I may ask

Thanks for helping
Keith

[Dnmatt]

It's not too noisy but I can slightly hear when it inside kicks on. I originally was going to use a 100 degree thermostat switch but decided to just hook it in parallel with the existing fan that was already thermostatically controlled. So now both fans come on when the coils get hot enough. I think I basically more than tripled the airflow across the coils.

I don't understand this statement "Their 3 pin fan controller also cant handle the high amp draw". The connector isn't handling any more current than what the fan draws which should be fine. Puzzling.

[Yoda]

It's not too noisy but I can slightly hear when it inside kicks on. I originally was going to use a 100 degree thermostat switch but decided to just hook it in parallel with the existing fan that was already thermostatically controlled. So now both fans come on when the coils get hot enough. I think I basically more than tripled the airflow across the coils.

I don't understand this statement "Their 3 pin fan controller also cant handle the high amp draw". The connector isn't handling any more current than what the fan draws which should be fine. Puzzling.

The fan controller cant handle two of the fans. I wanted to manually control two of those fans mounted flat, but if one is working for you than thats great. Do you have any photos or diagrams of how you wired your fan in to the thermostat.
Thanks
Keith

[Dnmatt]

Unfortunately I don't have pictures and the trailer is stored 1 1/2 hours away. Since our refrigerator is in the slide, there was already a thermostatically controlled fan installed on the coils. I just added this one in parallel which has much better airflow than the factory one does. It stays on for much shorter periods of time now versus when there was just the one fan.

[Scott'n'Wendy]

"The fans are rated 12V but can operate as low a 5V." This is a function of PWM and how the speed is varied. If you have a 12vdc supply and have it pulsed 'on' for 50% of the time, the fan 'sees' 6vdc and runs half as fast as full speed.


Just FYI Keith, PWM is very noisy to humans in the controllers I have experience with. But they were much higher voltages than 12v.

[rvoelker]

For me I'd be more worried about the noise level of the fan than what a couple extra volts(sometimes) will do to it's life span. 12Vdc computer type fans come in a lot of sizes and noise levels, not all of them being quiet.

My input on the input:
If you have a 2-wire or 3-wire fan and really want to lock the input at 12Vdc I would probably look at a step-down buck converter for a few dollars off of eBay. Quiet and simple - pump a range of volts in, it poops out only the target voltage (either a set/adjusted voltage or a fixed voltage). Shop for them by input voltage range and either output voltage or adjustable output voltage.
Here's one on eBay that is a bit fancier than you probably need that does what you're after for under about $10.00. It even gives you a output voltage meter! (...ohh, shiny/blinky lights!)
Here's another one from Digi-Key in a nicer package for a few more dollars (this is a low current device, see below)

If you have a 2-wire or 3-wire fan you can apply your source DC to the likely Red(+) and Black(-) and the fan will spin at it's designed RPM for that voltage.
- in a 3-wire fan the third wire(likely yellow) is a tachometer that some external circuitry would use to maybe figure out that the fan stopped spinning, or maybe adjust the supply voltage(PWM or what have you) to get to a desired RPM.
- in a 4-wire fan the fourth wire is used in conjunction with the tachometer and some external circuitry. It is an input from that external circuitry that does PWM to control RPM.

Another option is to build or buy a linear type voltage regulator. This style of regulator dumps the excess volts as heat. Can be cobbled/soldered together from one transistor(NTE966 / 7812) and 2-3 low cost other parts. ..shipping will probably cost more than the parts.

..keep in mind the current/amps portion of the story, too. I don't know what fan you're using but most computer fans don't draw very much so these little step-down buck converters should be fine.

[Yoda]

For me I'd be more worried about the noise level of the fan than what a couple extra volts(sometimes) will do to it's life span. 12Vdc computer type fans come in a lot of sizes and noise levels, not all of them being quiet.

My input on the input:
If you have a 2-wire or 3-wire fan and really want to lock the input at 12Vdc I would probably look at a step-down buck converter for a few dollars off of eBay. Quiet and simple - pump a range of volts in, it poops out only the target voltage (either a set/adjusted voltage or a fixed voltage). Shop for them by input voltage range and either output voltage or adjustable out put voltage.
Here's one on eBay that is a bit fancier than you probably need that does what you're after for under about $10.00. It even gives you a output voltage meter! (...ohh, shiny/blinky lights!)

If you have a 2-wire or 3-wire fan you can apply your source DC to the likely Red(+) and Black(-) and the fan will spin at it's designed RPM for that voltage.
- in a 3-wire fan the third wire(likely yellow) is a tachometer that some external circuitry would use to maybe figure out that the fan stopped spinning, or maybe adjust the supply voltage(PWM or what have you) to get to a desired RPM.
- in a 4-wire fan the fourth wire is used in conjunction with the tachometer and some external circuitry. It is an input from that external circuitry that does PWM to control RPM.

..keep in mind the current/amps portion of the story, too. I don't know what fan you're using but most computer fans don't draw very much so these little step-down buck converters should be fine.

Thanks I am still learning
Rich in post 1 I list a series of what some are calling step-down buck converter - other say different. Will any of those work. If I am understanding you correctly this one should work in either 3A or 6A https://www.amazon.com/dp/B09H264Z61...undefined&th=1 As I am mounting in the back of the fridge it could get wet (spray through vents) and dusty. Fan choices are running between .75 and 1.5 amps/pair - possibly a bit more if I go cooolerguys monster 120 mm 3500 rpm high flow IP67 one. Still researching I have the fans I am looking at are in this thread https://gdrvowners.com/forum/operati...tic-8cf-fridge

Scott Scott'n'Wendy I am aware of the noise. The stock fan is 44 to 48db and only runs full speed when on.Its not perfect but I can tolerate it. I am hoping to run the secondary ones lower, and only as needed. Thus the speed controller. And if I do need to crank them up during travel it wont matter. I just want to make sure I have enough airflow that I don't have a problem while traveling in 90-100 temps as I had on my trip. When stopped the fridge seem to recover even at those temps especially on 120V

This is all new to me so I appreciate any comments.

Thanks Keith

[rvoelker]

Keith,
Sometimes I need to kick my own ass for not reading...sorry.

The first link in your post, and the link in your recent reply (for the UTSAUTO DC 8V/40V to 12V 3A) looks pretty good to me

• 'water proof' enclosure
• 3A is sufficient assuming your total current draw of the fans is less than that. (don't have time right now to read your other post but you can run as many fans as you want off of one device provided the sum of their rated current draw is less(comfortably) than the device's output rating. If you have 1 pair of fans at 1.5amps you're fine. If you have 2 pairs at 1.5 you need to bump it to the 6Amp)
• Is described to take varying input to a fixed 12Vdc output..and that's the goal
• Offers a variety of safety features like over current/short circuit/over heat - all nice to have.

I don't think your fans are going to care whether you feed them a little ripple in the 12Vdc so whether it's a step-down buck converter or straight up PWM or a linear regulator is probably not a factor to sweat over, IMO.

Although I can't be sure from the Chinkadero English and every possible key word they used to describe it, I would expect this device is a step-down buck converter.

If you decide you want to minimize the impact of a couple extra volts over the life of the fans by controlling the battery bus voltage variances(which I personally wouldn't worry about..but that's just me) then this device should be fine/great for your application(grab one and if it doesn't work I'll send you a 6-pack).

[Yoda]

Keith,
Sometimes I need to kick my own ass for not reading...sorry.

The first link in your post, and the link in your recent reply (for the UTSAUTO DC 8V/40V to 12V 3A) looks pretty good to me

• 'water proof' enclosure
• 3A is sufficient assuming your total current draw of the fans is less than that. (don't have time right now to read your other post but you can run as many fans as you want off of one device provided the sum of their rated current draw is less(comfortably) than the device's output rating. If you have 1 pair of fans at 1.5amps you're fine. If you have 2 pairs at 1.5 you need to bump it to the 6Amp)
• Is described to take varying input to a fixed 12Vdc output..and that's the goal
• Offers a variety of safety features like over current/short circuit/over heat - all nice to have.

I don't think your fans are going to care whether you feed them a little ripple in the 12Vdc so whether it's a step-down buck converter or straight up PWM or a linear regulator is probably not a factor to sweat over, IMO.

Although I can't be sure from the Chinkadero English and every possible key word they used to describe it, I would expect this device is a step-down buck converter.

If you decide you want to minimize the impact of a couple extra volts over the life of the fans by controlling the battery bus voltage variances(which I personally wouldn't worry about..but that's just me) then this device should be fine/great for your application(grab one and if it doesn't work I'll send you a 6-pack).

Thanks - don't worry about the 6 pack - I have plenty of spare parts to add it to if it does not work. Thanks for taking the time to go over it.

[Jlawles2]

Yoda Keith, I'd have to ask questions on the waterproof one you linked. I know with some controllers, you have to adjust output based on input voltage. If you use an auto step up / down automatic then it may be a bit more reliable output. https://www.pololu.com/product/2577 came up when I did a quick look around. The deal with building robots and stuff so they have some neat stuff.