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?

 

I don't understand why you need to convert 240 volts AC down to 3 volts DC as the fan motor in most hair driers is a 240 volt series wound motor. I think there are a few hair driers an hand held vacuum cleaners that use high frequency brushless motors that may use a lower voltage than 240 volts but I don't think any will use as low as 3 volts. Can you give the FULL information on the model of hair drier you plan to modify.

Les.

 

I don't understand why you need to convert 240 volts AC down to 3 volts DC as the fan motor in most hair driers is a 240 volt series wound motor. I think there are a few hair driers an hand held vacuum cleaners that use high frequency brushless motors that may use a lower voltage than 240 volts but I don't think any will use as low as 3 volts. Can you give the FULL information on the model of hair drier you plan to modify.

Les.

I am following the very old thread mentioned before.
It said that the small fan motor use 3V dc. Also I checked the hair dryer and there seems totally two rectifiers, one on each switch, connected in series with the heating elements. So are you sure it runs on 240V ac?

And can you find a similar circuit diagram worked for the dryer I mentioned.
I find one on
https://www.etechnog.com/2018/10/how-hair-dryer-works-hair-dryer-circuit-diagram.html
but not sure that circuit is correct or not as the arrangements of rectifiers looks strange.

 

the fan motor in most hair driers is a 240 volt series wound motor.

I've known some where the heater element is tapped and used as a resistive voltage-divider to drive (via a diode) a low-voltage DC motor.

 

So how can I figure out what kind of my fan motor by opening and looking at it?

 

I've known some where the heater element is tapped and used as a resistive voltage-divider to drive (via a diode) a low-voltage DC motor.

Thanks. That is informative so that the motor may be a low-voltage one. But the design has to be re-done as I don't want the heating element consume as high as 3000W of electricity. I just want the strong wind.

 

You will need to take it apart and trace out how the heater and motor are connected. A picture of the motor would also give us some idea as to weather it is a mains voltage motor or a low voltage DC motor. If it is a DC motor it is likely to be a permanent magnet type. (Unless it is something like a Dyson.)

Les.

 

There are two rectifiers, one for each switch. Let me know what more you need.

 

The motor:

 

Looks to me like a low-voltage DC motor, plus 4 LEDs and some power diodes.

 

I agree with Alec that from the small part of the motor that we can see that it looks like a DC motor. Just because the one in the other post was 3 volts we have no evidence that this is also 3 volts. I suggest that you trace out the full schematic of the hair drier and post it. When we have seen that you may also have to measure the resistance of the heating elements.

Les.

 

Yes, the product has a DC motor when I buy it.
I will check to see if I can draw the circuit based on the wiring. You may draw one based on the photos.

But in such case, I cannot simply rewired to make it a strong wind blower?

 

If you don't want heat then you will have to replace the element with a suitable transformer or a switch-mode power supply.
You could try running the motor directly from 2 or 3 AA cells to get a feel for the likely voltage needed to get a decent speed, and if the motor is tending to overheat, but first you'd need to check which way the LEDs (if that's what they are) are connected so as not to put a reverse voltage across them.

 

The simple way to have this product be a cool air blower would be to disconnect the heater element connection, and do nothing at all to the motor connection. If the heater element is disconnected then it will not blow hot air. That is about as simple as it can be,

 

The simple way to have this product be a cool air blower would be to disconnect the heater element connection, and do nothing at all to the motor connection. If the heater element is disconnected then it will not blow hot air. That is about as simple as it can be,

If you read the threads the OP shows details of H.D. that use 24vdc motors complete with circuit diagram in post #3.
https://www.etechnog.com/2018/10/how-hair-dryer-works-hair-dryer-circuit-diagram.html
The OPs looks like a L.V. DC motor for sure.
Max.

 

The simple way to have this product be a cool air blower would be to disconnect the heater element connection, and do nothing at all to the motor connection. If the heater element is disconnected then it will not blow hot air. That is about as simple as it can be,

Another one for the list.

 

My hairdryer looks similar to the one as listed in
https://www.etechnog.com/2018/10/how-hair-dryer-works-hair-dryer-circuit-diagram.html
. If I just cut off the wires to the heating elements and remove it and possibly reconnect the wires ( assume they have to be in series), the motor will not be burnt and runs?

and 12V or 24V DC Motor. is considered a L.V. dc motor?

That is also why I choose to start with a hair dryer with a nozzle. But it looks too simple without considering any voltage drop etc in the idea?

 

. If I just cut off the wires to the heating elements and remove it and possibly reconnect the wires ( assume they have to be in series), the motor will not be burnt and runs?

and 12V or 24V DC Motor. is considered a L.V. dc motor?

If yours is wired as the link shows, or similar, disconnecting the heating element requires some other low voltage supply for the motor, small transformer etc.
12v - 24v is considered L.V.
Max.

 

I applied some dc source, such as an additonal USB port provided from some usb powered bluetooth speaker, to the two terminals of the motor and made it rotated. So, I may conclude that this motor is a low voltage dc motor and cannot be run directly from removing just the heating elements.
Perhaps a usb 5V usb adapter or some rechargeable battery charger can make it run instead of supplying 240V ac.

 

1. About the diode in each switch, can someone provide some explanation about that? Does that mean that the diode just cut half of the power cycle so that the power is reduced by half?

2. Yes, the motor seems to have some LED as some friends menton here. It does emit some blue light for a moment when I immediately connect it to the dc source but is not quite clear if it keeping emitting or not.

3. Whether the dc motor is run on dc or ac current?