I'm working on a Brushless DC Electronic Speed controller, and I have successfully implemented an open loop method by controlling the commutation rate manually. Obviously this won't work well for varying loads (which the propeller is just one load but winds and other factors I can't think of right now will easily cause it to fall out of open loop).
So I was attempting to do the Zero Cross Back-EMF detection method on a breadboard but there is so much noise most likely from various sources such as the fast switching digital signals from the PWM and other signals of the MCU coupling into the analog signaling. The wires on the breadboards can also act like little antenna and pick up no telling what EMI, and the breadboard with its various parasitic effects. I need a pretty decent Back-EMF signal to be able to do this method. So I am designing a PCB in Proteus Ares.
Now from what I understand, please correct me if I am wrong at any of this, is that you need two separate ground planes and they need to connect at single point somewhere where the analog ground plane kind of traps the analog current and the digital ground plane traps the digital current but with a small trace between the two so that they are pretty much still at the same potential.
Now my question is, do I need two separate power supplies? The way I have it now is a terminal block with 3 input; Positive from the 14.8 volt lipo battery, negative, and a rather low frequency analog signal (0 to 2.7 volt) for the control of the speed that will go to the ADC of the MCU. And another terminal block, 3 out, one for each phase for the BLDC motor.
Now I have an adjustable linear regulator that is taking the 14.8 V down to 3.3V for the MCU. Am I right to assume I should put this ground pin on the regulator on the digital ground plane since it will power all the digital components and the battery will basically be the power supply for everything really but will supply the analog components directly without any regulator....? Or am I wrong here..?
This is my first PCB I am designing and ordering. I can upload the Gerber files if needed or pictures of them.
Mainly I am just asking about different methods used to separate the analog and digital signals so there isn't interference when the two different components are placed on the same board.....?
I currently only have a 2 layer through hole board mostly designed because I was planning on buying the equipment and chemicals to etch my own boards but I decided to redesign it with 4 layers using a ground plane and power plane and SMT components. This way I can make the board a lot smaller and possibly put a large enough heat sink to cover the whole board for good heat dissipation keeping all the components cooler so I could run higher current, so faster and more RPM and maybe even overclock the MCU and ADC.
Should I put the ground and power planes in the middle layers or on the top and bottom with the signaling in the middle layers....? I've heard good things about both ways.
Well sorry if this thread is too long, but I appreciate any help and advice any of you can give me. If you have ever seen my other posts you know I have been working on this for a long time. It is because I don't have enough time to work on it much so I pick it back up whenever I can. But slowly and surely I will eventually get this done.
Thanks again,
Michael Walden
P.S. I know some of your are going to say use Google, but I just want some opinions from you guys. Some of you guys have been here a long time and I have much respect for the opinions here. I have read app notes on the subject but could not find anything particular to BLDC ESC PCB design of ground planes, if it even matters because I am sure mixed signal PCB design with mentioning of analog and digital ground planes would suffice.
So I was attempting to do the Zero Cross Back-EMF detection method on a breadboard but there is so much noise most likely from various sources such as the fast switching digital signals from the PWM and other signals of the MCU coupling into the analog signaling. The wires on the breadboards can also act like little antenna and pick up no telling what EMI, and the breadboard with its various parasitic effects. I need a pretty decent Back-EMF signal to be able to do this method. So I am designing a PCB in Proteus Ares.
Now from what I understand, please correct me if I am wrong at any of this, is that you need two separate ground planes and they need to connect at single point somewhere where the analog ground plane kind of traps the analog current and the digital ground plane traps the digital current but with a small trace between the two so that they are pretty much still at the same potential.
Now my question is, do I need two separate power supplies? The way I have it now is a terminal block with 3 input; Positive from the 14.8 volt lipo battery, negative, and a rather low frequency analog signal (0 to 2.7 volt) for the control of the speed that will go to the ADC of the MCU. And another terminal block, 3 out, one for each phase for the BLDC motor.
Now I have an adjustable linear regulator that is taking the 14.8 V down to 3.3V for the MCU. Am I right to assume I should put this ground pin on the regulator on the digital ground plane since it will power all the digital components and the battery will basically be the power supply for everything really but will supply the analog components directly without any regulator....? Or am I wrong here..?
This is my first PCB I am designing and ordering. I can upload the Gerber files if needed or pictures of them.
Mainly I am just asking about different methods used to separate the analog and digital signals so there isn't interference when the two different components are placed on the same board.....?
I currently only have a 2 layer through hole board mostly designed because I was planning on buying the equipment and chemicals to etch my own boards but I decided to redesign it with 4 layers using a ground plane and power plane and SMT components. This way I can make the board a lot smaller and possibly put a large enough heat sink to cover the whole board for good heat dissipation keeping all the components cooler so I could run higher current, so faster and more RPM and maybe even overclock the MCU and ADC.
Should I put the ground and power planes in the middle layers or on the top and bottom with the signaling in the middle layers....? I've heard good things about both ways.
Well sorry if this thread is too long, but I appreciate any help and advice any of you can give me. If you have ever seen my other posts you know I have been working on this for a long time. It is because I don't have enough time to work on it much so I pick it back up whenever I can. But slowly and surely I will eventually get this done.
Thanks again,
Michael Walden
P.S. I know some of your are going to say use Google, but I just want some opinions from you guys. Some of you guys have been here a long time and I have much respect for the opinions here. I have read app notes on the subject but could not find anything particular to BLDC ESC PCB design of ground planes, if it even matters because I am sure mixed signal PCB design with mentioning of analog and digital ground planes would suffice.