Turning a hairdryer into a COOL blower

SLK001

Joined Nov 29, 2011
1,549
Most of the hair dryers that I have gutted for parts had a 12-24V DC motor in them. They used the elements as a voltage dropping resistor to power the motors. These motors simply CANNOT be directly connects to the mains. Take the time to trace out the circuit to find out how your dryer works.

If you pull off the fan blades and pull the motor out of it's plastic holder, you will most likely find a motor number on it.
 

Thread Starter

Leon_Chan

Joined Sep 11, 2019
99
Providing I can get the motor number, where and what information I can get for the motor?
Will that provide the max voltage or current supported, etc?

Look like what I miss now is the voltage of the motor supported and
use an external step-down power adapter(or spare notebook charger that usually comes with 19V output dc)
to provide the power to the motor via either
1. the terminals that I tested using a dc source before or
2. the terminals the wires connect to the motor which may going through some rectifying elements (but not these diodes that we usually see)[ check with the photos ]
 

Thread Starter

Leon_Chan

Joined Sep 11, 2019
99


The circuit diagram is based on my understanding with some guess. (eg. the direction or positions of the two diodes may be wrong and the common connection appears to be the orange wire). It may be wrong. Please check if this will work or not.

swtiches:
s1 = off/low wind/high wind
s2 = low/medium/high temperature

P.s.
It looks like it is correct as the R2 is always connected when turn on so there is often a hot temperature and provide the voltage drop required for the motor .
 
Last edited:

SLK001

Joined Nov 29, 2011
1,549
Your schematic shows that the motor is a small voltage DC motor (because of the series diode, resistor and motor), so you will not be able to convert that particular model to "cool blow" only, unless you put in the appropriate transformer and bridge.

There are hair dryers that DO have a "cool blow" setting that would be quite easy to convert (do nothing - just put the switches in the correct setting!).
 

MaxHeadRoom

Joined Jul 18, 2013
28,617
If your H.D. is still intact, you could (carefully) measure the DC on the motor when it is running, then all you will need is a small AC source, transformer, and use the existing bridge rectifier, as shown in the schematic.
The bridge may be mounted on the end of the motor, if it is not a separate item.
Max.
 

MisterBill2

Joined Jan 23, 2018
18,167
Certainly you could even remove the heating element, but that may be a big effort. Just connecting to the blower motor and running it from a "wall wart" supply of a suitable voltage should be simple and easy and safe. How often do you get all three at the same time?
 

Thread Starter

Leon_Chan

Joined Sep 11, 2019
99
The cost of power consumption by the heating element is expensive compared to this cheap dryer shipped from China. That is why I don't want to keep it.
So the best practice here I would like is to remove the original ac plug and using an adjustable voltage from the "wall wart" supply so I will power up the motor with dc. That may also be a spare notebook charger that usually supply power of 19V dc?
 

Thread Starter

Leon_Chan

Joined Sep 11, 2019
99
When there is no heating element, it should work just like a fan.
Anyone has a circuit diagram of such dryer with a cool button, this would be different.
 

shortbus

Joined Sep 30, 2009
10,045
My hair dryer has Hot/Off/Warm and a burst of cool air switch.
Mine does too, only problem is I don't have any hair now to use it on. But then again mine has a universal type motor and not a DC motor. Don't know when they changed but to make them cheaper they started using the heat coils to reduce the voltage for the motor. DC motors are much cheaper than AC motors.
 

Thread Starter

Leon_Chan

Joined Sep 11, 2019
99
Finally, I follow up this with my recent measure of the voltage drop using multimeter across the dc motor. That is about 28V dc.

So I can find a dc power supply in the range 12V to 24V dc, such as from an outdated LCD monitor or a notebook power supply that may provide about 18V dc and connect it to the motor.

I will have to disconnect the heater elements wiring to the dc motor too so in case it take up any power.

I heard people saying the blower is not designed for continual use, not having mentioned that if that apply to the motor or the heating elements. So does that apply also to my change? Any advice?
 

Thread Starter

Leon_Chan

Joined Sep 11, 2019
99
Recheck the wiring diagram I had written. It looks like there is no rectification of the power to the dc motor. This seems something is wrong. Either that motor is not a dc one or I missed the rectifiers in it.

In the past, you may detect a dc motor running if you have a CRT televsion. So how can we detect it now?
 

Thread Starter

Leon_Chan

Joined Sep 11, 2019
99
Does anyone has these numbers how fast in rpm a dc motor run, for 12V and 24V ? And compare that with an ac motor of similar size.
 

LesJones

Joined Jan 8, 2017
4,174
You can't make such a comparison. Motors are designed to run at the required speed for the application they are made for.
From your post #9 one od the pictures of the motor shows that it is a DC motor and there IS A BRIDGE RECTIFIER mounted in the end of it. (I don't know what the four square white components are that look like surface mount LEDs.)

Les.
 
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