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Controlling hair dryer


ChiefCodeX

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Another idea is to restrict the air going into the blower which will control the air going out. Just a simple disk of sheet metal or even cardboard which can cover the intake, providing you have disabled the heating elements. I made a disk of sheet steel over a blower intake on one of my forges, works great. Lots of good advice regarding safety please read and heed you can't be too safe!

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caveat: if you restrict the intake on something like a hair dryer(I wont pretend to know anything about a proper forge blower) the motor can potentially overheat as it will experience resistance it was not designed for in that condition, much better to divert a portion of the blast AFTER the blower than to restrict the intake.

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caveat: if you restrict the intake on something like a hair dryer(I wont pretend to know anything about a proper forge blower) the motor can potentially overheat as it will experience resistance it was not designed for in that condition, much better to divert a portion of the blast AFTER the blower than to restrict the intake.

 

That's the intuitive reasoning but it's actually reversed. A blower moves air, restricting either the intake or outlet reduces the air being moved so the motor is doing proportionally less work. The louder whine you hear is the blower spinning faster, not the motor working harder.

 

Hair drier motors rely on the blower moved air for cooling but if we're restricting all the air we turn them off instead so that's not a big thing.

 

Frosty The Lucky.

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Admanfrd, 

 

The GFCI disconnects the circuit when it detects an imbalance of 4-5 milliamps which indicates current has found a path to ground - possibly through a person.

 

A typical home circuit fuse is likely to be 15 to 20 Amps.  The 5 milliamp rating is just below the threshold of killing a person under the best of circumstances  A 15 Amp circuit provides 3,000 times that much current before the fuse blows. 

 

Beyond that, two wire systems (as in your dimmer)  lack the back up grounding conductor which is an important failsafe for the primary overcurrent system to function.  This can lead to dangerous situations where metal parts are electrified and just waiting for a path to ground.  

 

Alternating current can cause muscle spasms preventing you from letting go of an energized part.  It can also cause involuntary motions of your arms and legs.  Manyf electricians are killed every year by falls that follow a non-lethal shock.  It's not too far fetched to imagine shocking yourself on your forge and landing on hot metal, anvil hardies, or whatever else.  Stay safe.

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That's the intuitive reasoning but it's actually reversed. A blower moves air, restricting either the intake or outlet reduces the air being moved so the motor is doing proportionally less work. The louder whine you hear is the blower spinning faster, not the motor working harder.

 

Hair drier motors rely on the blower moved air for cooling but if we're restricting all the air we turn them off instead so that's not a big thing.

 

Frosty The Lucky.

 

Ah, thanks Frosty, I was thinking primarily in terms of operating with the intake partially covered to choke the blast and the subsequent reduced volume of air available to cool the motor, not using the cover to fully choke (turn off) the system.

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Ah, thanks Frosty, I was thinking primarily in terms of operating with the intake partially covered to choke the blast and the subsequent reduced volume of air available to cool the motor, not using the cover to fully choke (turn off) the system.

 

I know what you were thinking, we've all thought that about blowers. The motor won't lack for cooling unless all the intake is blocked and if we want the air reduced to zero we just turn it off.

 

A gate valve is probably the best way I know of to control the air from an electric blower without the added stress of an electric controller, even cycle limiters. (whatever they're properly called)

 

Heck, the first time someone told me blocking the air flow made life easier on the motor I called B.S. Then I tried it and darned if I didn't have to post my results and thanks. Am I weird for appreciating my mistakes?

 

Frosty The Lucky.

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How is a dimmer SWITCH any safer? what starts the electricity flowing through metal (can't figure how to word that). You said it could be electrified waiting for a path to ground? what damages the circuit? or the switch rather. I have the cord wrapped in heat resistant sheets and buried.

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Weird, no, not for that reason anyway ;) just makes you a good learner :)

Speaking of which, thank you for the schooling!

 

Schooling? Aw heck, we're all passing knowledge along, it's what we're here for. Life is school or it's short enslavement.

 

Well, some of us are here to learn. The kids are being kids, happy to demonstrate how smart they are with their almost utter lack of useful knowledge. The current discussion reminds me of the bumper sticker you see now and then, "Hire a teenager NOW while they still know everything." If we can just keep him from killing himself or someone else I think he might make a pretty good smith. He certainly has quite the imagination and isn't afraid to experiment and tinker. I think I was in my mid 20's before the old saying, "You have two ears and one mouth for a reason" sunk in.

 

We've had a few spectacularly successful young men come here for basic help, mostly the home schooled I believe but not all I'm sure.

 

I guess I was really lucky in my selection of parents. Playing the dumb game with Mother was a sure way to be humiliated, publicly if we were playing the game in public. Dad would just let us try what we thought would work with just enough guidance to keep the blood loss to an acceptable level. Seriously, he'd let us blood ourselves to learn something.

 

They didn't take well to the change the subject game either, especially combined with the playing dumb. For example, trying to transfer the argument from how dangerous a circuit breaker is to what's wrong with MY setup, I wrapped the cord in tape and buried it argument. Would've gotten one of two responses from my folks. Dad would've let me get bitten by the current; that happened more than once till I learned to let HIM do it or at least listen to his directions. Or Mother would just eviscerate me verbally for trying to play dumb in so foolish a manner. You just didn't want to embarrass Mother by being stupid, that disappointed look was worse than any spanking.

 

Sorry for getting into ramble mode. . . Again. <sigh>

 

Frosty The Lucky.

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How is a dimmer SWITCH any safer? what starts the electricity flowing through metal (can't figure how to word that). You said it could be electrified waiting for a path to ground? what damages the circuit? or the switch rather. I have the cord wrapped in heat resistant sheets and buried.

 

If you buried the cord,  I relay hope you used UF type wire, also the heat resistant warping is creating a fire hazard.  I hope you are joking   :o and I hope your parents know what you are risking.   In addition to violations of US-NECA, the national Electrical code is written to prevent death from fires, and other not so fun stuff.

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Admanfrd.  I never advocated a dimmer for motor control.  Dimmers are intended for lights, not motors.  Motors come in a huge variety of configurations- not all of which are applicable to speed control.  Dimmers limit the voltage applied to a lamp by wasting current into heat via a variable resistor.  No electricity is saved by running a dimmer - it's simply trading brightness for heat.

 

Operating a motor at a reduced voltage increases the current flowing through the windings of the motor.  Excessive current (measured in Amps) raises the temperature of the windings causing the insulation to break down.  This ranges from shortened motor life to outright burning the motor depending on the situation.

 

Motors built for variable speed use are more complex to make and have higher temperature ratings on their winding insulation.  There are other more complex solutions to this situation but I don't want to bog things down.

 

Electricity will follow the path of least resistance, knowing that electrical distribution systems are built to shut the flow as soon as a fault is underway. The third wire of a three wire system gets connected to every metal part tied to the system.  The intention is that if either of the current carrying conductors find a fault path to something conductive - the system will short out and blow the fuse (or trip the breaker).  Lacking that third wire - a situation can present itself where a part get's energized and there's no path to ground to force it to short out.

 

Mod addition: Meaning you will become the path to ground when lacking a grounding system

 

There are many approved methods for installing circuitry.  What you're describing is not among them.  I encourage you to seek the assistance of a local and qualified electrician.

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  • 3 years later...
  • 2 years later...

This thread is a bit old, but it is on my radar these days. I'm in the process of building a charcoal side blast and I think I will be using a hairdryer for the bellows. I think the easiest solution to the problem of excess air is a simple mechanical exhaust of some kind. It is easy enough to rig a movable hose/pipe that has infinite adjustment from directly inline with the end of the blow pipe (maximum air) to complete bypass blow pipe (zero air). The tried and true shutter methods for blocking off portions of the air flow are also simple systems.

I, however, want to alter to hair dryer to remove the A/C components and leave the simple DC motor. A battery, a switch and a speed controller is all it will take to make a nice little electric bellows. This does away with dimmer switches, GFCI issues, and other bugbears associated with line voltage. I have found numerous youtube videos about hair dryers: how they work, what each part does, etc. so the correct information is available. Simple DC controllers are very cheap online and come in several flavors. I think I priced a simple one at 4 bucks. Hair dryers are pretty easy to find at goodwill or other such resale places for very little money, as well. I have seen someone on IFI already do this mod, and I am hoping he updates us on how his rig is serving him over the long haul.

 

Taylor

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Frazer, was mostly recapping what has already been said on this thread. I was hoping the member who rigged a dc motor with a controller would chime in. He may be busy. Are you anywhere near RIT? Ah, back in the day, Shop 1 was a flagship fine craft spot. I mostly know if from my clay life, but I'm betting metal folks will remember it as well.

Does anybody else have a battery powered motor being used for bellows? I'd be interested in seeing the setups for this type of hack. All the physical hacks are great and simple and well documented here.

Taylor near Jeddo TX

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I've been picking up blower type mattress inflaters at yard, garage etc. sales for a couple years now, most are 12v dc but a few are 120v ac.  You can find them in the sporting goods section of the big boxes like Wally World, last I checked under $20. They make probably 5x the air a blow drier does and being DC should be easily controllable.

Frosty The Lucky.

 

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Yep, RIT is ~25 minutes from me. I would've gone there for college but I ended up going to Clarkson to get a little further from home.

I took apart a hairdryer the other night to better answer your question and the one I took apart had a little permanent magnet DC motor in it. It was pretty simple, just a switch,  the heater coils and a full bridge rectifier at the input to the  motor. There was not a capacitor at the output of the rectifier, so what the motor is seeing is a bumpy DC voltage. But a DC motor doesn't really care.

Some of the high end professional hairdryers use an AC motor, but most of the cheap ones are going to be set up more or less the same as the one I took apart.

If you want to control the speed of the motor, PWM  (pulse width modulation) is the easiest way to do it. There is a lot of info out there on that topic. You can't, well I suppose you could, but you shouldn't just use something like a potentiometer to change the speed of the motor. In a nutshell, voltage=speed, amps=torque, if you reduce the speed of the motor with a pot, you are also lowering the torque which will likely cause problems. 

You may as well just keep the fan and the housing since it has already been engineered for that little motor and it's one less thing to think about. 

I use a hairdryer for my forge, but I use mechanical methods to adjust the air since I find it easier to do, but to each their own.

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PWM will be here Monday. 12v battery=easy peasy. Already earned my how-a-hairdryer-works degree from the Tubes. Gutted the wife's hairdryer before I realized I could use it as is just to see how it worked. Oh well.

I'll post the set up in my JABOD thread when I finish it. The air compressor hose is a real pain.

 

T

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