If the motor has brushes then itis a universal motor and it will run on DC and AC. THAT is why it is called a UNIVERSAL motor. It will run better on DC and put out a bit more power. And it will run quite well on 18 volts DC.
IN a blow-dryer application the motor is cooled by the air stream passing over it and so if you are running it as a cool air blower that should work quite well, if you still have the air flowing over the motor.
BUT if you change the blower so that the motor is directly powered from a DC supply you will need to change the plug-in end of the cord so that it does not get connected directly to the mains, since that will not work correctly after the change.

 

So the wiring diagram is wrong. It missed the details and I forget most of it.

Yes, looking back at the photos on #9, there should be the black diodes on the top of the motor and as I remember the white ones are LED lights.

Two of the terminals of the motor has been soldered. I measured the voltage drop using the other + and - terminals.

I think it is hard to just add the blow circuit to the existing one and everything can messed up. And it is dangerous if I forget about what is inside it.

 

I like the idea of
"Turning a hairdryer into a COOL blower" as discussed in the very old thread:
https://forum.allaboutcircuits.com/threads/turning-a-hairdryer-into-a-cool-blower.21823/

I would like to make one strong wind cool blower to blow away dirty air spread from the nearby environments from time to time. I will do it based on a hair dryer ( with its very high rotational speed compared with some big sized fans ) with two switches. One turns on-off/low/strong wind and another low/high heat.
So if I want to bypass the heating elements. I need to reconsider the design just to bring a 240V ac down to 3V dc?
How can I do that safely?

Stop futzing with it. Simply remove the heating coil altogether. the fan should still run and it will blow non-heated air.

 

Mine has a COOL switch, but it's momentary.

 

Stop futzing with it. Simply remove the heating coil altogether. the fan should still run and it will blow non-heated air.

Maybe... Some hair dryer motors depend on the heating coil (or portion thereof) to drop the voltage from the source (line voltage). If you were to simply remove the heating coil, the blower motor wouldn’t run.

 

Maybe... Some hair dryer motors depend on the heating coil (or portion thereof) to drop the voltage from the source (line voltage). If you were to simply remove the heating coil, the blower motor wouldn’t run.

Indeed- probable.



In which case, instead, remove the coils and use appropriate capacitors before the bridge rectifier to drop the current. Put appropriate resistors in place of the coils.

 

After using an external power supply was suggested I commented that it should work well with a universal motor. And it would.

 

There seems no simple way to integrate the new blower only circuit to the existing hair dryer circuit without creating additional problems. You get either a hair dryer or just a blower.

The conclusion is to make it only a blower only circuit by cutting the existing wirings and connect the motor with the dc power directly.

 

This is DELETED as the attempt to integrate the hair dryer and the blower would confuse most people even myself.

 

That is a very dangerous way to modify the hair drier as the 18 volt DC connection wire will be at mains voltage when the dryer is used in normal mode. (My original understanding of your post was that you wanted to CHANGE the function to just blow cold air rather than add a cold blow function.) Why not just buy a hair drier that has the cold blow function ?

Les.

 

Yes, OK. I have marked that as DELETED. The modification should have completed. I just buy another cheap one to use as a hair dryer.

 

That is a very dangerous way to modify the hair drier as the 18 volt DC connection wire will be at mains voltage when the dryer is used in normal mode. (My original understanding of your post was that you wanted to CHANGE the function to just blow cold air rather than add a cold blow function.) Why not just buy a hair drier that has the cold blow function ?

Les.

There was NEVER ANY MENTION of keeping the normal heated dryer function.
The description was CONVERTING a hair dryer into a cool air blower. At that point there would no longer exist the mains connection to the device. With no possible means of mains connection there should not be any possibility of a hazard.

 

There was NEVER ANY MENTION of keeping the normal heated dryer function.
The description was CONVERTING a hair dryer into a cool air blower. At that point there would no longer exist the mains connection to the device. With no possible means of mains connection there should not be any possibility of a hazard.

That is about a DELETED post which I attempt to add the dc circuit to the existing one.

 

After I created a cool blower from my hair dryer, I am left with its heating coil element. So I want to get some idea how to create a hand warmer using a usb to micro 5V power bank with this heating coil. I just need to warm up the coil for a short time, so I do not want to include a sensor to detect risen temperature. Btw, there are already some videos of this on youtube.

I have no idea how much resistance value of this coil. So anyone guess what is its value?

 

The label on the hairdryer should have specified the rating, from which the element resistance can be calculated.

 

Be5fore going any farther, consider the power available from that 5 volt power bank. Consider both output watts available and the amp hours available. They limit the maximum heat you could possibly get under any condition.
If the hair dryer was a 600 watt device and the mains voltage was 120, then the current was 5 amps.

With 5 volts the current would be 1/24 of that 5 amps, 5/24 amps, around 200 mA, and at 5 volts, then the power would be 5V x 5/24A= watts, about 1 watt.

Is one watt enough power to provide any useful hand warming effect? I am not sure, but it does not seem like very much.

 

I wouldn’t use the entire coil. If you knew how many watts you need to create enough heat to warm your hands, you could measure the resistance of the coil and calculate how many inches to use.


Or I’d determine it experimentally. With a bench power supply, I’d apply power along the coil’s length to determine how much to use.

Once you’ve determined the length, you know the bolts, ohms and current needed. Then, you can specify a battery pack. Or not. You may find it’s infeasible.

 

I got a reading of about 500 ohm of this coil from my not-reliable multimeter. That is why I want a guess from you.

It seems now reasonable as the hair-dryer is powered by 240V ac with about 24V drop across the dc motor. It is quite hot in its original state.
Look like it is true that the 5V from the power bank may not get hot with this resistance value which I think may need some 500k ohm??? Or do we need to replace it with some 100k resistors connected in series as in some youtube video?

The hair dryer has a max power rating of 2000W. Let me know in case you still need other data?
The output of most power bank may be just 5V at 2A Max.

However, I did read about news how these USB LED lights get hot, when it is powered from the 5V usb ac adapter. So this may be another idea for getting heat from the 5V power bank. I try to make a hand warmer for my personal use only, when I am feeling very cold.

Below are some reference so there may be more discussions:
USB Hand Warmer Review & Teardown Pebble Hands Treasure NS-518 mobile Power Supply

Mini Pebble Hand Warm Charging Treasure Explosion-Proof Mobile Power Bank
https://handok-speaker.en.made-in-c...easure-Explosion-Proof-Mobile-Power-Bank.html

P.S. 1 - power bank capacity: 3.7V, 5000 mAh ( the size of this will not make it so heavy )

 

I got a reading of about 500 ohm of this coil

Way off. Your element resistance is 240²/2000 = 28.8Ω.

 

Here is another video about a hand warmer on the market.
Can one deduce the resistance value of that heating element? Or is that heating element working as a resistor only?

Inside a heated power bank. (That gets very hot!)