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Variable speed triggers, how do they work?

Go to solution Solved by Hackentosher,
5 hours ago, akio123008 said:

First of all, it's an ordinary brushed DC motor, so the speed is simply controlled by the voltage applied to it, just like the motor in a cordless drill.

Exactly, that's why I want to know what kind of speed controller this is, and what kind of components it uses. Here's a picture, it's just one of those triggers for cordless drills.

IMG_2786.thumb.JPG.9477f47938dbc0b9eeeab50dc73ebfd7.JPG

I know most semi-conductor based electronics don't like overvolting that much, but the thing looks quite rugged and well made so I suspect it may get the job done.

Oh I think those are linear actuated potentiometers. Measure the resistance of the leads with the trigger depressed, and undepresssed. It might be something like a few megaohms undepressed and little to no resistance fully depressed. That way you can directly control the voltage going to the motor. 

 

As for voltage, it probably won't care too much. 

I'm putting an electric motor on my bicycle, and the speed controller I'm planning to use is a trigger from an old corldless drill. It's rated for 16 volts, and I'm planning to use it on 24 volts. I'm guessing it's fine, but since I don't know how a speed trigger like this works, I have no idea what kind of electronics are inside, and therefore I'm not sure how much tolerance for overvolting there is. I hope someone on this forum knows how one of these triggers works. Also, no I have not taken it apart, and there's a good reason for that, the entire thing is a solid block of plastic, and taking it apart is almost impossible. Even if i'd succeed at doing so, I'd probably also break it.

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2 hours ago, akio123008 said:

I'm putting an electric motor on my bicycle, and the speed controller I'm planning to use is a trigger from an old corldless drill. It's rated for 16 volts, and I'm planning to use it on 24 volts. I'm guessing it's fine, but since I don't know how a speed trigger like this works, I have no idea what kind of electronics are inside, and therefore I'm not sure how much tolerance for overvolting there is. I hope someone on this forum knows how one of these triggers works. Also, no I have not taken it apart, and there's a good reason for that, the entire thing is a solid block of plastic, and taking it apart is almost impossible. Even if i'd succeed at doing so, I'd probably also break it.

Usually overvolting electronics that much is not a good idea. You may blow some kind of voltage regulator, MOSFET, or the caps by throwing too much voltage into it. Typically electronics can take a couple hundred millivolts, but much more than that may make things get hot or even let the magic smoke out. It's hard to say without knowing what the controller is and what components it uses and the maximum voltages of them

 

Also make sure your motor controller can control the kind of motor you're using. If you have a DC motor, you need a DC motor controller. If you have a BLDC motor, you need a BLDC controller, they are two very different types of motors and operate in very different manners. Do you have some pictures of the motor and controller you have?

ASU

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First of all, it's an ordinary brushed DC motor, so the speed is simply controlled by the voltage applied to it, just like the motor in a cordless drill.

13 minutes ago, Hackentosher said:

It's hard to say without knowing what the controller is and what components it uses and the maximum voltages of them

Exactly, that's why I want to know what kind of speed controller this is, and what kind of components it uses. Here's a picture, it's just one of those triggers for cordless drills.

IMG_2786.thumb.JPG.9477f47938dbc0b9eeeab50dc73ebfd7.JPG

I know most semi-conductor based electronics don't like overvolting that much, but the thing looks quite rugged and well made so I suspect it may get the job done.

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5 hours ago, akio123008 said:

First of all, it's an ordinary brushed DC motor, so the speed is simply controlled by the voltage applied to it, just like the motor in a cordless drill.

Exactly, that's why I want to know what kind of speed controller this is, and what kind of components it uses. Here's a picture, it's just one of those triggers for cordless drills.

IMG_2786.thumb.JPG.9477f47938dbc0b9eeeab50dc73ebfd7.JPG

I know most semi-conductor based electronics don't like overvolting that much, but the thing looks quite rugged and well made so I suspect it may get the job done.

Oh I think those are linear actuated potentiometers. Measure the resistance of the leads with the trigger depressed, and undepresssed. It might be something like a few megaohms undepressed and little to no resistance fully depressed. That way you can directly control the voltage going to the motor. 

 

As for voltage, it probably won't care too much. 

ASU

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6 hours ago, Hackentosher said:

Oh I think those are linear actuated potentiometers. Measure the resistance of the leads with the trigger depressed, and undepresssed. It might be something like a few megaohms undepressed and little to no resistance fully depressed. That way you can directly control the voltage going to the motor. 

 

As for voltage, it probably won't care too much. 

All right then, I'll just hook it up and find out if it works. Since it's just an old trigger that isn't used for anything else anyway, I won't mind if it blows up.

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7 hours ago, Hackentosher said:

Oh I think those are linear actuated potentiometers. Measure the resistance of the leads with the trigger depressed, and undepresssed. It might be something like a few megaohms undepressed and little to no resistance fully depressed. That way you can directly control the voltage going to the motor. 

 

As for voltage, it probably won't care too much. 

It tends to be based on a sliding potentiometer but there has to be some electronics in there too to power the actual load. Simply putting the potentiometer in series with a serious load is impossible. For example, at half speed the potentiometer would roughly dissipate the same power as the load, for a typical cordless drill that would be tens of watts.

 

For mains AC powered drills there should be a triac and the potentiometer would control the phase angle. For DC cordless drills there should be a MOSFET and the potentiometer controls PWM duty cycle. So simply trying to measure resistances won't work. (Or it could simply be the potentiometer and the electronics where external)

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  • 8 months later...

My B&D drill has a variable trigger that got stuck. I managed to open it but can't tell if there's anything wrong with it. 

I'm not sure how the different parts should be placed. 

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15690718475042508786004793158257.jpg

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