Running a box fan off of stagepin

[Swade White]

Hello everyone, we recently got this new haze machine but the haze reaches only about half the stage and then it fades away. Also, we want to hang the haze machine so it is not in the way for the actors walking in the wings. This creates another problem of the haze rising above the electrics and not creating the effect that we want. Our current solution is to set a box fan on the top of the hazer angled down at the ground so it blows the haze across the stage and down towards the stage. This completely solves our problem but my question is, can I take off the edison plug and replace it with a stagepin plug so we can "dim" the motor of the fan? I would like to be able to control the fan from the board (which is an ETC Element) instead of unplugging and plugging in the fan. Thanks!

 

[Amiers]

I wouldn't take the end off. I would make an adapter cable.

Also I wouldn't Dim the fan as you prolly won't see a difference. Would set the channel to FL @ 1 profile.

 

[Les]

If you dim the fan, you run the very real risk of burning up the motor and possibly causing a fire. The way variable speed fans work is by using a different set of windings for each speed. In this case, you would likely cause the winding in use to heat up much more than normal since less energy is being used to turn the rotor. This manifests as heat. Not to say I haven't seen it sort-of work - I just don't think it's worth the risk and box fans have super cheap-o motors in them to begin with, so it might not end well. Is the low speed setting too high?

I would put the fan on a relay (same way you are powering the haze machine?) or at least use a profile as @Amiers suggested.

 

[EdSavoie]

I'm curious as to by what mechanism it would burn up, wouldn't less voltage from the dimmer cause current and heat to also drop off?

Also, couldn't kickback from the fan harm the dimmer?

 

[RonHebbard]

I'm curious as to by what mechanism it would burn up, wouldn't less voltage from the dimmer cause current and heat to also drop off?

Also, couldn't kickback from the fan harm the dimmer?

Lower-RPM-of-the-motor-could-amount-to-lower-inductive-reactance-(impedance)-thus-drawing-increased-current-generating-more-heat.-With-apologies-for-my-non-functioning-space-bar.
Toodleoo!
Ron.Hebbard.

 

[JChenault]

I'm curious as to by what mechanism it would burn up, wouldn't less voltage from the dimmer cause current and heat to also drop off?

Also, couldn't kickback from the fan harm the dimmer?

My understanding is the following

AC motors are designed to turn at a fixed speed. It takes a certain amount of energy to turn the shaft at that speed. ( let's assume that is 100 watts for illustration). At 120 volts, the wires in the motor are carrying about 0.8 amps. ( 120 times 0.8 ~= 100)

At 50 volts the motor is still trying to draw 100 watts but the motor is trying to draw 2 amps (50times 2 =100).

Are the wires in the motor designed to survive 2 amps long term? Probably not.

 

[BillConnerFASTC]

Under (design) voltage on motors, like in a brown out, cause motors to burn out. Do you need to know more?

 

[Swade White]

Alright thanks everyone. The lowest setting on the fan was too powerful but we are working on just moving the fan farther away from the hazer.

 

[len]

Maybe you'll get lucky and find a dmx controllable fan used. New they're $$$ and if you're using a box fan I'm assuming money is an issue.

 

[Swade White]

Maybe you'll get lucky and find a dmx controllable fan used. New they're $$$ and if you're using a box fan I'm assuming money is an issue.

We will just have to keep experimenting with different setups because unless we can find a really cheap fan with dmx in it, we probably won't be getting one.

 

[RonHebbard]

Alright thanks everyone. The lowest setting on the fan was too powerful but we are working on just moving the fan farther away from the hazer.

Or.leave.the.fan.where.it.is,assuming.it's.working/for.you.where.it.is.and.partially.block.it.off.reducing.its.air.flow.with.a.mechanical.damper...A.time.honored.tradition.in.the.HVAC.industry...With.apolgies.for.my.broken.space.bar...I.dispatched.a.minion.for.a.new.keyboard.this.morning.
Toodleoo!
Ron

 

[Swade White]

Or.leave.the.fan.where.it.is,assuming.it's.working/for.you.where.it.is.and.partially.block.it.off.reducing.its.air.flow.with.a.mechanical.damper...A.time.honored.tradition.in.the.HVAC.industry...With.apolgies.for.my.broken.space.bar...I.dispatched.a.minion.for.a.new.keyboard.this.morning.
Toodleoo!
Ron

Our hazer is the Chauvet Amhaze II and I am wondering could we just simply turn the blower on it around so it blows down with the built in fan? Or would fluid leak out?

 

[Amiers]

IF it catches condensation in it then yes if you turn it upside down it will drip.

My suggestion is to get some plastic and make another section that you can bolt onto the current section. Black is current section and make a piece to slide over and point at whatever direction you want it to go.

 

[Swade White]

IF it catches condensation in it then yes if you turn it upside down it will drip.

My suggestion is to get some plastic and make another section that you can bolt onto the current section. Black is current section and make a piece to slide over and point at whatever direction you want it to go.
View attachment 14300

Alright thanks for the tip, I will try this out tomorrow.

 

[JD]

You can slow down induction motors safely but it's a pain! What you have to do is lower the frequency. Had some real fun with an audio generator and a Crown DC300 power amp. The motor speed is directly proportionate to the frequency, so 30Hz gives you half speed. The technique is as old as the hills. Old 45rpm Jukeboxes often contained a mix of 45 rpm records and the mini 33 rpm albums. A switch on the mech would sense the smaller hole and kick the motor onto an "autospeed" unit, which simply put out 120 volts at a lower frequency.

What burns motors up is running them at a lower voltage. As the rpm drops, the induction winding falls out of phase and the motor is technically in a partial stall, causing the winding impedance to plummet and current draw to skyrocket.

 

[Swade White]

You can slow down induction motors safely but it's a pain! What you have to do is lower the frequency. Had some real fun with an audio generator and a Crown DC300 power amp. The motor speed is directly proportionate to the frequency, so 30Hz gives you half speed. The technique is as old as the hills. Old 45rpm Jukeboxes often contained a mix of 45 rpm records and the mini 33 rpm albums. A switch on the mech would sense the smaller hole and kick the motor onto an "autospeed" unit, which simply put out 120 volts at a lower frequency.

What burns motors up is running them at a lower voltage. As the rpm drops, the induction winding falls out of phase and the motor is technically in a partial stall, causing the winding impedance to plummet and current draw to skyrocket.

Even if it is trying to draw a lot of electricity wouldn't the dimmer stop it from happening since it is only outputting a certain amount of volts to the fan?

 

[RonHebbard]

Even if it is trying to draw a lot of electricity wouldn't the dimmer stop it from happening since it is only outputting a certain amount of volts to the fan?

In.a.word:..NO!..Extend.this.to.where.your.motor.is.stalled.and.consider.what.happens.to.its.power.consumption.and.heat.generation.
Toodleoo!
Ron.Hebbard...(Still.apologizing.for.my.inoperative.space.bar.)

 

[Swade White]

In.a.word:..NO!..Extend.this.to.where.your.motor.is.stalled.and.consider.what.happens.to.its.power.consumption.and.heat.generation.
Toodleoo!
Ron.Hebbard...(Still.apologizing.for.my.inoperative.space.bar.)

Alright, looks like I am going to try turning the blower upside down and catching the condensation with a plastic bag. You need to get a new space bar sometime