Electric Ducted Fan Jets Discuss electric ducted fan jets here including setup tips, power systems, flying techniques, etc.

Ducted Fan Newbe

Old 10-14-2019, 01:34 AM
  #1  
fjc191
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I am working on a project that would require a 50 mm ducted fan to operate at top speed for about 10 seconds, twice a week. Would you offer some advice. Everything I read indicates that a speed controller be placed between the fan and the lipo battery. First, the fan has three wires coming out of it. Please explain what each one does. Secondly, is a speed controller needed or can the fan be connected directly to the switched battery?
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Old 10-14-2019, 01:54 AM
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Wildflyer
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First thing, I am not trying to be rude, but you need to learn a lot about brushless motors before you go much further.

The three wires are the connections to the windings inside the motor, they are all the same.
A brushless DC motor is actually a 3 phase AC motor, the power comes from the battery and goes into an ESC Electronic Speed Control. The ESC sort of chops up the battery voltage and sends it to the motor in the proper way. Very complex.
The motor WILL NOT run without an ESC
The common ESC's must be driven by a throttle comand from a RC radio system.
You can get ESC's designed for E-scooters and E-skateboards They do not require a radio system.

10 seconds twice a week would not bother an EDF as long as you follow the limits on voltage. The timing could be worked out many ways.
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Old 10-14-2019, 06:38 AM
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Very informative and certainly not rude. Funny how things get names: Speed Controller (and more)(ESCAM). Instead of using a radio throttle command to operate the ESC, is there a physical part of the ESC that could be restrained in the position of desired operation?
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Old 10-14-2019, 09:22 AM
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To run any brushless with Radio :

Servo Tester.

The setup would basically be :

Battery (given the short run and infrequent use - I would suggest NiMH or LiFePo battery)
+
ESC >>>>>> this would have its radio plug in a Servo Tester to provide control
+
Motor (EDF)

The servo tester would not require additional power as the ESC would have its BEC to do that.

May we ask what this 10 secs 2x a week is for ?
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Old 10-14-2019, 09:28 AM
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solentlife
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Brushless Motors as already mentioned are basically an offshoot of AC format. The 3 wires are sequentially powered to create a turning moment within the magnets of the case. Which wires are plugged to which of controller determines direction of rotation. To change - you swap over two wires.

Brushless motors MUST use a Brushless ESC to control ... they cannot be connected direct to battery.

If you want a simple ON - OFF fan system - then you would use a BRUSHED motor - a Brushed motor can be simply connected to a switch and battery for simple ON-OFF. If full only power is required - the brushed would not need a speed control (ESC).
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Old 10-14-2019, 11:17 AM
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fjc191
An EDF is designed to be as light and powerful as possible to enable it to fly a plane.
If your project is ground based there are other more efficient ways to move air about unless that specific fan diameter is absolutely vital.
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Old 10-14-2019, 01:22 PM
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ron_van_sommeren
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Originally Posted by fjc191 View Post
I am working on a project that would require a 50 mm ducted fan to operate at top speed for about 10 seconds, twice a week. ...
Why? What is the project? The more info you gave, to more specific and better the replies can be.
E.g. why do you need high-speed air?
E.g. do you need a small volume moving at high speed (ducted fan) or bigger volume moving at low speed (cooling fan)?
Power from a battery or from a power supply?

A brushless motor connected directly to DC is a massive short.

Last edited by ron_van_sommeren; 10-16-2019 at 10:49 AM.
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Old 10-14-2019, 04:46 PM
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fjc191
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Thanks all

Fred
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Old 10-14-2019, 04:56 PM
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What I need is a way to move air that would result in a high pressure on the downstream side. Volume of air is not that important and could be compensated by duration of operation. I was looking at the EDF to achieve high pressure and I thought high volume relative to time. In my current configuration, I am using a 120 v hair dryer (with the heating guts removed). It works pretty good but I would like to address portability by converting the power source to rechargeable batteries.
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Old 10-14-2019, 05:51 PM
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Hair dryer .... large volume but relatively low pressure.

EDF .... moderately high pressure and moderate volume.

If its replacing a Hair Dryer - then its not something sophisticated in setup. But compared to a Hair Dryer that has handle / design form to make it convenient to hold etc ... any EDF setup is going to look mickey mouse !
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Old 10-15-2019, 07:06 PM
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I now understand the brushless motor will not work without an ESC therefore, the advice given to use a brushed motor would simplify things. It seems brushed motors with and EDF would not make sense due to weight considerations. In my case, weight is not a consideration. I would like to put together a 50mm EDF with a brushed motor. Is there a supplier who manufactures such a thing? If not, how would I go about doing this?
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Old 10-15-2019, 09:23 PM
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Turbojoe
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Originally Posted by ron_van_sommeren View Post
Why? What is teh project? The more info you gave, to more specific and better the replies can be.
E.g. why do you need high-speed air?
Like Ron said, exactly what is it you're trying to accomplish? Without knowing the requirements for the fan any suggestions given will be nothing more than wild guesses. Good luck finding a brushed motor for a 50 mm fan now that will perform even near as well as your hair dryer. I have a few of the old GWS brushed 75 mm fans that will barely fly a very clean 350 gram plane. Brushless motors with an ESC can be had now for pocket change. You're just chasing your tail trying to use a brushed motor especially with an EDF that small.

Joe
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Old 10-15-2019, 09:48 PM
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fjc191
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I understand the ESC would be controlled by radio signal. There is not a radio in the plans. Is there a ESC that would function at full speed and provide the 3 phase characteristics required for the brushless motor without the necessity for a radio signal?
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Old 10-15-2019, 10:01 PM
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Turbojoe
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Originally Posted by fjc191 View Post
I understand the ESC would be controlled by radio signal. There is not a radio in the plans. Is there a ESC that would function at full speed and provide the 3 phase characteristics required for the brushless motor without the necessity for a radio signal?
It doesn't HAVE to use a radio signal. As Nigel said in an above post you can use a servo tester to achieve the same goal. You then have full control of the RPM the same as if you used throttle stick on a transmitter. Search eBay or Hobby King for "servo tester" and get one that suits your needs. Why the continued secrecy for your project? I seriously doubt anyone here will steal and try to profit from your idea.

Also, where are you located? Don't need your home address, just a general area. One of us could be local and willing to help you out with your project.

Joe
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Old 10-15-2019, 10:53 PM
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fjc191
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Joe,

It was not clear to me exactly what Nigel was describing (my bad, servo tester can be used to control motor speed also, huh). I just looked at a youtube video and I think I got it .



1 Battery connected to ESC (1 black, 1 red)
2 EDF connected to ECS (3 wire output from ECS)
3 Servo Tester connected to ECS (1 red wire)

Thanks again for your patience.

Fred
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Old 10-15-2019, 11:27 PM
  #16  
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The servo testers I have looked at are rated for

Input: DC 4.5-6.0V

The 3s battery has about 12v when fully charged. Is that an issue?
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Old 10-16-2019, 01:40 AM
  #17  
quorneng
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fjc191
If the ESC has a battery eliminator circuit (BEC), most simple ones do, it also provides the power at a regulated 5V to work the servo tester.
In a radio control setup this BEC provides the power at 5V for the receiver and the plane's servos. The BEC is completely independent to the voltage supplied by the ESC to the motor.

You are aware that a LiPo battery requires a specific 'LiPo' battery charger. Using any other type of charger can lead to the LiPo bursting into flames.
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Old 10-16-2019, 02:32 AM
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Answer appreciated and understood. I have a LiPo charger.
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Old 10-24-2019, 01:43 AM
  #19  
fjc191
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I got all the stuff we discussed including a servo tester, ESC and a 50mm EDF. Hooked it up and all is well....pushing some air.

Now the question of switching. I had planned to switch the circuit on by connecting the battery. But, it seems the servo tester needs a moment of time to self test, adjust or whatever.

With the servo tester turned up to full speed and the circuit completed by connecting the battery, the EDF jumps very slightly every few seconds and beeps at varying intervals and pitch..sometimes one jump (beep) sometimes more but it does not "engage" to full speed as the position setting on the servo tester should dictate. It doesn't rotate at all.

After a few seconds when the servo tester is adjusted to zero and then raised to a higher level, the EDF responds as expected.

How could this be switched on and off without a manual adjustment of the servo tester?
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Old 10-24-2019, 02:30 AM
  #20  
quorneng
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fjc191
I think you will find it is not the servo tester but an ESC safety feature that is doing this. The ESC is programmed so you cannot accidentally have full power set when you connect the battery! The ESC will simply not respond until the throttle signal has first been set to the fully closed position.
I don't know if there is a way round this safety feature or if there is whether the ESC could actually stand an instant full power start.
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Old 10-24-2019, 02:37 AM
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fjc191
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With the battery connected to the ESC and the EDF (servo tester not connected), the EDF beeps constantly. Now,under these conditions, if the servo tester is connected, the EDF responds as expected. Then, when the servo tester is removed from the circuit, the EDF continues operating for about 4 seconds.
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Old 10-24-2019, 11:18 AM
  #22  
solentlife
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Originally Posted by fjc191 View Post
The servo testers I have looked at are rated for

Input: DC 4.5-6.0V

The 3s battery has about 12v when fully charged. Is that an issue?
Blimey - you really are making a meal of this.

Your connection in previous to last post is WRONG ...
Second .. the radio plug will supply the 5V to the tester from its BEC circuit. The full battery power will go via the second circuit of the ESC to the motor.

1. Connect ESC 3 wires to EDF motor 3 wires.
2. Connect ESC Radio plug to Servo Tester - it will be powered through that same plug as well as Tester sending 'throttle signal'.
3. Connect two wires of battery to two wires of ESC.

Turn knob on Tester and see direction of EDF ... if needs reversed - swap any TWO wires ESC to motor.
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Old 10-24-2019, 01:44 PM
  #23  
fjc191
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solentlife

As stated in my initial post, "50 mm ducted fan to operate at top speed for about 10 seconds". What was not stated is this action would be activated by a simple manual switch (turn on switch, EDF turns on--turn off switch, EDF turns off).

The problem is the ESC will not come on in a "full power" position. As I stated previously, "With the servo tester turned up to full speed and the circuit completed by connecting the battery, the EDF jumps very slightly every few seconds and beeps at varying intervals and pitch..sometimes one jump (beep) sometimes more but it does not "engage" to full speed as the position setting on the servo tester should dictate. It doesn't rotate at all. "

My connections are exactly as you re-stated. I have simulated what you have stated with the results you indicated. I can connect everything (switch simulation) and nothing happens until I adjust the level of the servo tester. This does not accomplish the original objective i.e. (turn on switch, EDF turns on--turn off switch, EDF turns off). If it is a requirement that the servo tester by adjusted, after the switch is activated, this would not accomplish the initial objective of one action (switch) to turn the EDF off/on without other adjustments.

With the items, previously outlined, is there a way to operate the EDF with a simple on/off switch?

Thanks for you help

Fjc191
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Old 10-24-2019, 02:14 PM
  #24  
solentlife
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You cannot operate a Brushless with simple ON .. OFF ... not with an ESC ...

Not that I know of anyway. The problem is that ESC needs to initialise at IDLE before it can command anything. That is why you get the BEEPS when first powered up.
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Old 10-24-2019, 02:31 PM
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Fjc191
"With the items, previously outlined, is there a way to operate the EDF with a simple on/off switch?"

Not using an ESC and a brushless motor. They are simply not designed to do this.

If you changed the brushless motor for a brushed type an ESC is no longer needed so it can be switched on directly. However EDFs as used in a plane really need the power to weight and performance of a brushless motor so it is likely a brushed motor will not be a simple swap. You may have to 'engineer' the change yourself.

With more detail of what you are trying to achieve there may be other ways to obtain the airflow you require.
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