I have a circuit board from a brushless motor (fuel pump). For major components, it has 4 Power FET's (HEXFET IRFU3410) and 3 Hall Sensors (Honeywell SS461A). I have attached datasheets. It also has (I think) 3 Transistors, 3 diodes (2 one size and another larger), 5 resistors, and a capacitor..... I might have missed a few things.

Could anyone point me in a direction of a similar design that uses only 4 FET's and 3 Hall Sensors without a DSP. I keep trying to search on Google but do not know what terms to search for..... This is a very simple motor control circuit and I am interested in duplicating it.

Thanks for the help.

 

Search for BLDC motor control.
Fairchild, Freescale (Motorola), IR and others all have app notes on controller IC's.
Those hall sensors are latching type, so you need a motor/drive that is compatible.
Max.

 

I am having trouble finding anything with only 4 Power FET's?

 

I am 100% sure your board has six fets on it.

Unless its using this scheme of drive: http://www.google.se/url?sa=t&rct=j...=iT47z20iiqPirdsEggtvyQ&bvm=bv.53899372,d.bGE

 

That's the part that I don't understand. There is definitely only 4 Power FET's. It also has 3 other small transistors of some other type (very small). I have no idea how they are being used (might not be part of the H-Bridge?). I see if I can get some pictures to help describe. I think that Unipolar .PDF is the closest thing ive seen......

 

Do you have the motor the board came off available?
Max.

 

So I just checked the three unknown tiny transistors under a microscope. The label seems to be 702 S. So I', pretty sure it's some type of N-Channel MOSFET. Does this make sense? 4 Large Power FET's and 3 smaller FET's? Maybe I do have a 6 FET Bridge after all? But what would the other large Power FET be used for? This is getting me more confused.....

 

So is there a method of control that involves a 6 FET Bridge and Hall Sensors that does not use a DSP/DSC ???

 

You mean other than the likes of MC33033 dedicated IC's etc?
Max.

 

yes. controlling without a dedicated IC ?

 

This is one way: http://www.w1ngselectronics.com/index.php?page=schematic

 

I have attached diagrams of the board, top and bottom (after I smashed it out of its housing). It is a very simple circuit with few components. I would like to understand the operation so I can duplicate it here at home. I am having trouble determining how these 20 components are controlling a 3 phase brushless motor without a DSP? Can anybody explain or reference a similar design/schematic?

 

Your first photo clearly identifies 3 pairs of power mosfets. That is all you need for 3 half bridges, which will drive a 3 phase motor.

 

I understand that is all that is needed for control. But I cannot find any examples/schematics online that show 6 FET's (3 Pairs) used with hall sensors but without a DSP/DSC. Im trying to create this schematic.....

 

It seems the board/motor you have is very similar to the type of motor used in HVAC etc now, labeled a ECM (Electronicall Commutated Motor).
You may find something in this area of search?
Unfortunately many of these motors that have the controller in the endbell come with the board potted, so it is very hard to reverse-engineer.
Max.

 

yes this was obviously potted.... I smashed it with a hammer. I figured it was a pretty common/simple 3 phase brushless design. Only has 20 components and does not have a processor of any type. I am trying to figure out how the FET's are being switched without a processor/driver circuit that im used to seeing. Im assuming the Hall Sensors are directly connected to the FET's but I am having trouble finding any similar designs/schematics that show this....

 

I believe GE were the pioneers of the application of the BLDC version now known as the ECM, they traditionally have been secretive with their proprietary designs, hence one reason for potting, maybe?
Max.

 

yes, the potting was to protect the board from fuel and chemicals but was probably to protect the design as well ;-/ It just seams to simple to not be floating on the internet somewhere.....

 

Basically I am looking for a 3-Phase Brushless 6 MOSFET (N-Channel) design that uses 3 Hall Sensors and does NOT use a micro-controller. Everything online that I find has a micro-controller. The design I am looking for is much easier and I would think very common....

 

Personally I would imagine anyone looking to implement a BLDC drive without having to implement with Dsp programming, would tend to use one of the LSI IC's dedicated to this application, whether it be a OEM or individual?
It would be my inclination anyway.
Max.