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Topic: Brushless motor: Why do I need an ESC? Alternatives (Read 1 time) previous topic - next topic

Hello,

I'm learning Arduino in order to build a specific device, which includes 4 fans to circulate air. I thought I'd use old PC fans, and replaced the motor in project 10 of the Arduino starter kit with a PC fan.

Project 10 uses an H bridge L293D to control a DC motor with a pot and 2 buttons; one to switch on/off and one to change motor direction. Pot is speed.

First thing I learned was that there are brushed and brushless motors :). But, it worked, which was great, but in my research this morning I've come across all sorts references that you absolutely must use an ESC to control a brushless motor. I'm perfectly happy to buy one but don't know which one to buy :)

Can anyone shed a little light please on what the equation is I'd use to judge what sort of wattage ESC to buy?
Also, how come a brushed motor will rotate both ways but my brushless one would only go one way round? Is this related to using the wrong code and I should be using servo code to control a brushless motor?

Many thanks for your time
Photography nut trying to make the flux capacitor of macro pho

Erdin

There is no simple answer, it depends on what motors you have.

Normally a brushless motor requires an alternating current.
http://en.wikipedia.org/wiki/Brushless_DC_electric_motor
But some brushless motors have electronics inside and can be powered with a DC voltage.

Fans as used in a PC have often a microcontroller inside (like a tiny Arduino inside the fan). Some of those fans allow a PWM signal, either at the 12V pin, or a seperate pwm wire. Some older fans don't allow a PWM signal, but can be regulated with a linear regulator. Some fans have an outside variable resistor.

A Servo motor is a motor with a gear and with electronics. It reacts to pulses. The motor inside the servo could be a brushed or brushless motor.

You probably heared about stepper motors, but did you know there are also coreless motors ?

Thank you Erdin, appreciated!

Could you recommend any websites or reading that'd take me into the various types of motors and motor controllers, their advantages disadvantages etc? I'm just after some cheap and cheerful fans with speed control to drive air round some apparatus. The speed control is to control the noise as much as their output... a bit bewildered by the permutations that seem to be cropping up between h bridge, motor shields, integrated electronics, ESCs etc.

Many thanks again!
Photography nut trying to make the flux capacitor of macro pho

MarkT

Brushless motors are usually 3-phase and come in two main varieties - sensored and sensorless.  All the brushless motors for RC aircraft, quadcopters etc are sensorless, which means a special controller is needed to determine when to commutate the windings using the
back EMF on the 3rd (unpowered winding).  They are also very high current motors, way beyond the capabilities of a L293D (think 10 to 100A),
designed specifically for very high power density and running from LiPoly batteries via a matching ESC.  Such motors cannot run slowly as
the back EMF is insufficient.  Quality is variable, prices are cheap.

The other sort are sensored BLDC motors (extensively used in industry), which have hall-effect magnetic sensors to commutate even when
stationary - these motors are designed for running for decades reliably in industrial environment and are usually superbly engineered and
very very expensive as a result.  They are often the basis of industrial servo motor, where an encoder and feedback circuit controls the motor
to allow fast accurate positioning (even more expensive).
[ I won't respond to messages, use the forum please ]

mamette

How if we not use ESC and use L6234 IC? like this guy:

http://www.youtube.com/watch?v=QSBBGl-4x40

and this guy too:

http://www.youtube.com/watch?v=PXYfY3ZcJjU

MarkT


Thank you Erdin, appreciated!

Could you recommend any websites or reading that'd take me into the various types of motors and motor controllers, their advantages disadvantages etc? I'm just after some cheap and cheerful fans with speed control to drive air round some apparatus. The speed control is to control the noise as much as their output... a bit bewildered by the permutations that seem to be cropping up between h bridge, motor shields, integrated electronics, ESCs etc.

Many thanks again!


In that case you want PC fan with speed control input.
[ I won't respond to messages, use the forum please ]

Chagrin

Computer fans that are brushless will normally have the speed control (the "ESC") built into the fan. Driving them with an L293 should still work fine, but there's still a minimum threshold voltage you must supply to get them to start spinning (e.g. 6V is when a 12V fan starts spinning).

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