Turning a hairdryer into a COOL blower

SLK001

Joined Nov 29, 2011
1,452
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
15
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
15


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
1,452
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
18,871
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.
 

Thread Starter

Leon_Chan

Joined Sep 11, 2019
15
Looking at a sample spec sheet on
https://miro.medium.com/max/1322/1*8s9xhrCgSBq44ukb7Ns9pw.jpeg
.
The nominal voltage is the only data I need for the motor.

Is there any way to estimate or calculate this value ? Or it is just 12V or 24V?

Yes, it is better to have replaced the power source.

While the original idea of eliminating the heating element is simple but how to implement this is another thing.
 

MaxHeadRoom

Joined Jul 18, 2013
18,871
The idea by @shortbus has its merits as you could have the plug-in power supply external to the dryer.
I would apply a 12vdc source to get an idea of fan air volume, if less than original, use 24vdc.
Or less if too high.
Max.
 

MisterBill2

Joined Jan 23, 2018
3,721
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
15
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
15
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.
 
How is the air when the switch is on, is the air as present air or a little cool?
My dryer has an SPDT Center off switch labeled warm-off-hot and an SPST momentary, that turns off the heating element + an integrated GFCI
Then an overtemperature thermal fuse. The intake filter is easily cleanable. It's an old CONAIR dryer.
 

shortbus

Joined Sep 30, 2009
6,890
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.
 
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