Portable radiator fan?

[cyan88]

I'm in the middle of building a portable air purifier and have a radiator fan I'm hoping to be able to connect to a power cord so that it can be easily plugged into a wall socket. It's a 12V 7.5A draw electric radiator fan. I talked to some people and have a potentiometer to be able to adjust the speed and a switch but I'm having trouble finding a transformer that can handle the amperage. Is this just too large to be hooked up how I propose or should I be looking for a different power option? I've been searching through different power cords I have but I really don't totally know what I'm doing with all of that.

Also, I'm not sure of the order from fan to socket but have an idea. I believe it's going to be:
Fan->potentiometer->switch->transformer->wall
correct? I just need to find a transformer above 7.5amps?

Thanks ahead of time,
New here

 

[KeepItSimpleStupid]

You need a 12 VDC power supply > 7.5 A e.g. https://www.trcelectronics.com/Cosel/power-supply-pla.shtml

You will also need a PWM speed control. This might work: https://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_120539_-1

Reducing the voltage doesn;t work, The fan may not start and as you reduce the voltage. With PWM, the torque is at the same as if 12 V was applied cotinuously, but the speed can be varied.

ebay may be a good source of parts.

 

[cyan88]

Thank you for your help, I'm considering myself a little out of my league. I've done some arduino projects but the PWM instructions on setting it up basically ruled it out for me. If I hooked up that power supply (12VDC 8.400Amp) I would just need to find an appropriate cord to handle that level of amps to the wall, correct?

Not sure if this is how threads normally go on here but like i said I'm out of my league so please bare with me.

 

[KeepItSimpleStupid]

If I hooked up that power supply (12VDC 8.400Amp) I would just need to find an appropriate cord to handle that level of amps to the wall, correct?

You MIGHT be better with a 10 A supply. Not sure. the PWM thing does have a slow start, so that will help. I've used it.
it is a KIT though.

Wall no. Power = V*I so 12 * 10 (really 7.5) * 1/efficiency

Efficiency is likely 85%+ or so for a switching supply.

So, it's like 120+ W. At 120 VAC 120 W is 1 Amp.

So, any power cord is basically going to work.

The fan connections would have to say be 16-14 AWG. www.powerstream.com has a calculator.

PS: Didn't feel like doing the math or looking up the efficiency specs.

I do know that motors need a brief high current to start. Sometimes this current can shut down a power supply. A slow start PWM helps that a lot.

 

[cyan88]

So if I tried my hand at the PWM it would be connected between the fan and the power supply correct? I'm confused on the power cord comment. Can I just repurpose a three-prong power cord (what i understood from you saying any cord will work) to go from the power supply to a socket or what do I need between?

 

[alec_t]

Tempting though it is to re-use the radiator fan, there are two things worth considering:
1) The cost of the proposed supply and PWM controller will probably be greater than that of a conventional mains-powered fan,
2) The radiator fan may well be rather noisy.

 

[cyan88]

True, probably over reaching to not have to start all over but I think that would be best at this point.

 

[audioguru]

Make and post a video of the DC fan smoking when you feed it AC from a transformer. Also record its loud HUM.

When I was a teenager I made a fan using a motor with brushes. Knock, knock on my door came the RF cops! They said my fan made interference on hundreds of radios and TVs around me. We had a long talk about electronics then they took away the "fan". The neighbours who called the RF cops bought a real new fan for me.