Brushless/Bi-directional

I am curious if someone would be able to tell me if you can get
bi-directional brushless ESC's. I am currently working on a senior
design project. The project includes blimp-like characteristics and I
am looking at brushless DC motors for weight:trust efficiency. I have
searched many forums and sites, but I only seem to find Brushed motor
ESCs that are reversible with respect to changing wires physically. I
assume when I see a picture of a bi-directional ESC with two wires
going to the motor that this would be a brushed motor setup. We need
bi-directional thrust mainly to turn and stop the robot.
Can anyone help guide me in the right direction in finding a
bi-directional ESC for a Brushless motor? Thank you.
Brian
Reply to
Traffibm
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| but I only seem to find Brushed motor ESCs that are reversible with | respect to changing wires physically.
There are plenty of brushed ESCs out there that can do reverse. They're generally found on cars and boats rather than planes, but they're out there, and should work fine for your application if you used brushed motors.
| I assume when I see a picture of a bi-directional ESC with two wires | going to the motor that this would be a brushed motor setup.
A good assumption. Generally, two wires = brushed. Three wires = brushless (and sensorless). Three wires + 5 more little wires = brushless with sensors.
| Can anyone help guide me in the right direction in finding a | bi-directional ESC for a Brushless motor?
For brushless motors, I know of no reversable ESCs. The best place to look would probably be somewhere that caters to R/C cars, but brushless motors aren't big with R/C cars yet (as they're generally prohibited by the racing rules.)
Generally a brushless setup (sensorless, which most are now) can be reversed by simply reversing any two of the three motor wires. If you could wire up a relay or something to reverse two wires for you, you could have reversing that way. Just make sure that your reverser can't only leave only two wires connected -- that's a good way to burn up your ESC. Also I'd make sure that you don't reverse while the motor is running -- that sounds like a recipe for frying something too.
This may be obvious, but most of the airplane props we use aren't very efficient when reversed. But they'll still generate some (back) thrust, so that may be fine.
Reply to
Doug McLaren
| Generally a brushless setup (sensorless, which most are now) can be | reversed by simply reversing any two of the three motor wires.
I forgot to mention this, but there's another option as well.
In the past few months, vendors have started selling variable pitch prop setups for small electric 3D planes, and they work with brushless motors, usually outrunners.
Basically these planes can reverse their thrust mid-flight -- not by reversing the motor, but by changing the pitch of the prop with another servo. That might work for you, but then you've got additional servos to mess with.
Though just googling for `brushless esc reverse' found several ESCs that might be what you need --
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they all claim to support running the motor in reverse -- I don't know if that means you can go reverse on the fly or if you can just swap the wires like I mentioned before.
Reply to
Doug McLaren
Brian-
The Mamba brushless power package from Castle Creations provides for reversing direction. It is for R/C cars, but nothing inherently different in it to preclude using in in an aircraft as you intend. There are doubtless others - the vendors you need to look at are suppliers to the R/C car market. Airplanes don't generally need reversing motor systems.
Abel
Reply to
Abel Pranger
| Generally a brushless setup (sensorless, which most are now) can be | reversed by simply reversing any two of the three motor wires.
Thanks Doug, I have found many to claim to support reverse, but on many of sites that I have found, I looked into and found they are infact refering to swapping two of the three wires. I will still check those recommended sites nonetheless. I was thinking of looking for some type of relay device but I was not sure where to look. I was going to contact an electronics guru here at the univeristy about that tomarrow to see if he can think of anything I can use.
| Basically these planes can reverse their thrust mid-flight -- not by | reversing the motor, but by changing the pitch of the prop with | another servo. That might work for you, but then you've got | additional servos to mess with.
Thanks for the tips about looking into the variable pitch setup! That actually sounds like it could be the solution that I need. I will have to check weight specs first. Thanks for your input
Reply to
Traffibm
Abel-
I will look into some R/C car ESCs, I knew that cars and boats (R/C) used reversible ESCs but just from a glance looked heavy and large. I am eager to look at some because I am wondering if I could strip some of them down in weight if they have any casings or anything. I was mainly looking at airplanes but you are right that they generally wouldn't need a reversible motor. Thanks for the suggestion!
Reply to
Traffibm
| | Basically these planes can reverse their thrust mid-flight -- not by | | reversing the motor, but by changing the pitch of the prop with | | another servo. That might work for you, but then you've got | | additional servos to mess with. | | Thanks for the tips about looking into the variable pitch setup! That | actually sounds like it could be the solution that I need. I will have | to check weight specs first.
They're really quite light.
Though if it were my project, I'd just get two good quality brushed motors and two car ESCs with reverse, rather than messing with a variable pitch prop. But the variable pitch prop would certainly give you faster response times going from forwards to backwards -- the prop doesn't even have to slow down.
Reply to
Doug McLaren
Brian,
Try this brushless controller design group:
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And/or this design discussion:
Vriendelijke groeten ;-) Ron van Sommeren 14th. int. electric fly-in, Nijmegen, Netherlands, June 25
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Reply to
Ron van Sommeren

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