How does Drag Brake work? What's the principle?

[Campaign000]

I've gone through but no result.
I know ESC control the motor by voltage, but I have no idea how the drag brake works, the adjustable drag brake implements. Could anyone give me some details in physics? Thanks in advance.

[paintballer9876]

Magic

Well the way i understand it the esc simply shorts out the motor.

[Narly1]

ESC's use a PWM (pulse width modulation) scheme for both acceleration an braking. In acceleration, the power to the motor is switched on and off at a very high rate. The ratio of power on time to power off time (aka duty cycle) controls motor speed. The more of the time the power is on, the faster the motor goes.

Similarly, in braking the electrical short across the motor is switched on and off at a very high rate. The ratio of short applied time to short disconnected time (aka duty cycle) controls braking power. The more of the time the short is applied the more powerful the braking.

The drag brake setting is simply the amount of braking power applied at off-throttle.

If you could instantly move your trigger finger from acceleration to a consistent braking position (value) when you wanted to perform a stop maneuver, you would be accomplishing the same thing as the drag brake setting.

Narly1

[Campaign000]

Originally Posted by paintballer9876

Magic

Well the way i understand it the esc simply shorts out the motor.

How to explain the adjustable drag brake if just simply short out?

[JohnRobHolmes]

There are three ways to do it. First is to short the motor. This just builds up heat in the motor and any electronics in the loop. Not efficient, and only as effective as the motor allows. Added resistance in the system decreases drag power. The second way is to use the battery as a load for the motor, in essence trying to charge the battery when the motor turns. Same as regen braking, only brakes are available at neutral throttle too. This is most efficient, but it is limited by the motor design and loop resistance. The third method used with my Holmes Hold mode is an active brake, which uses power to brake the motor. With the magic of a specialized waveform with PWM control and a tidy feedback loop, it allows for instant hold in either direction by injecting voltage opposite to the motor's spin. Not the most efficient, but the most effective.

[JohnRobHolmes]

Originally Posted by Campaign000

How to explain the adjustable drag brake if just simply short out?

PWM, AKA duty cycle. If you only short the motor 50% of the time, you only get half strength brake.

[Campaign000]

Originally Posted by Narly1

ESC's use a PWM (pulse width modulation) scheme for both acceleration an braking. In acceleration, the power to the motor is switched on and off at a very high rate. The ratio of power on time to power off time controls motor speed. The more of the time the power is on, the faster the motor goes.

Similarly, in braking the electrical short across the motor is switched on and off at a very high rate. The ratio of short applied time to short disconnected time controls braking power. The more of the time the short is applied the more powerful the braking.

The drag brake setting is simply the amount of braking power applied at off-throttle.

If you could instantly move your trigger finger from acceleration to a consistent braking position (value) when you wanted to perform a stop maneuver, you would be accomplishing the as the drag brake setting.

Narly1

Thanks Narly. Your words made a great explanation!

[Campaign000]

Originally Posted by JohnRobHolmes

There are three ways to do it. First is to short the motor. This just builds up heat in the motor and any electronics in the loop. Not efficient, and only as effective as the motor allows. Added resistance in the system decreases drag power. The second way is to use the battery as a load for the motor, in essence trying to charge the battery when the motor turns. Same as regen braking, only brakes are available at neutral throttle too. This is most efficient, but it is limited by the motor design and loop resistance. The third method used with my Holmes Hold mode is an active brake, which uses power to brake the motor. With the magic of a specialized waveform with PWM control and a tidy feedback loop, it allows for instant hold in either direction by injecting voltage opposite to the motor's spin. Not the most efficient, but the most effective.

Great appreciation John for the full information! suddenly enlightened.

[inginear]

Originally Posted by paintballer9876

Magic

Well the way i understand it the esc simply shorts out the motor.

Originally Posted by JohnRobHolmes

..... The third method used with my Holmes Hold mode is an active brake, which uses power to brake the motor. With the magic of a specialized waveform with PWM control and a tidy feedback loop, it allows for instant hold in either direction by injecting voltage opposite to the motor's spin. Not the most efficient, but the most effective.

looks like it really is magic!

[Narly1]

Originally Posted by Campaign000

Thanks Narly. Your words made a great explanation!

Thanks for the compliment. One of things I like to do with my posts is to try and explain concepts in a way that anybody can understand them.

BTW, I edited my original reply a bit, adding the term "duty cycle", just to make things a bit clearer.

Narly1

[Campaign000]

Originally Posted by Narly1

Thanks for the compliment. One of things I like to do with my posts is to try and explain concepts in a way that anybody can understand them.

BTW, I edited my original reply a bit, adding the term "duty cycle", just to make things a bit clearer.

Narly1

Thanks man

[day215]

How much does the motor factor into the strength of the drag break? I have my CC MMP set to 213% DB strength, my motor got a little hot one day and the DB doesn't seem as strong. What should one look for in a motor regarding DB?

[JohnRobHolmes]

The magnet strength and steel concentration has a lot to do with the drag, with exception to using my Holmes Hold brake. The weaker the magnets, the weaker the passive drag. The lower the steel flux, the weaker the drag.

[CreepyCrawl]

Originally Posted by JohnRobHolmes

The magnet strength and steel concentration has a lot to do with the drag, with exception to using my Holmes Hold brake. The weaker the magnets, the weaker the passive drag. The lower the steel flux, the weaker the drag.

So would this mean that a motor not holding, even on a maxed out speedo setting, is outfitted with magnets and steel of lower or inferior quality?

Or is there a trade off at play with magnet choice? For example, do weaker magnets yield smoother low end throttle input?

[Narly1]

Originally Posted by CreepyCrawl

So would this mean that a motor not holding, even on a maxed out speedo setting, is outfitted with magnets and steel of lower or inferior quality?

Either that or they have somehow become demagnetized to some extent, overheating being the worst culprit.

Narly1

[JohnRobHolmes]

Lower strength magnets do not always indicate inferior quality, but in many cases it may be true. Overheated magnets are certainly weaker.

Weaker magnets can give a better low speed control if other aspects of the motor design and speed controller allow for it. That is why I haven't produced any neo magnet brushed motors. I built some and just couldn't get the low end I desired without compromising other design aspects. Hopefully Eddie has techniques that I didn't try that can hit that sweet spot.

[ROCKEDUP RICKY]

I know if your eletronics don't work in Colorado ,you throw rocks at the rig and some how this will fix it. I've never tried it but I know thats what they do in Colorado. I think they even have a rock throwing club or click of some kind. I've seen it in their sigs and avatars.

[JohnRobHolmes]

It must be the rocks. Special magnetic rocks or something.

[skid plate]

Originally Posted by ROCKEDUP RICKY

I know if your eletronics don't work in Colorado ,you throw rocks at the rig and some how this will fix it. I've never tried it but I know thats what they do in Colorado. I think they even have a rock throwing club or click of some kind. I've seen it in their sigs and avatars.

Priceless........................








JC

[Rubbaneck]

Originally Posted by ROCKEDUP RICKY

I know if your eletronics don't work in Colorado ,you throw rocks at the rig and some how this will fix it. I've never tried it but I know thats what they do in Colorado. I think they even have a rock throwing club or click of some kind. I've seen it in their sigs and avatars.

Originally Posted by JohnRobHolmes

It must be the rocks. Special magnetic rocks or something.

magic rocks! Just here to bring a smile to your day...