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This may seem like a dumb question, but does anyone have a schematic for a BDCM controller. All I seem to be able to find are partial schematics or schematics that include a micro controller. My customer has specifically requested no micro controllers. The customer is also governed by the FAA and for them to be able to use the controller they are required to show manufacture capabilities. I'd hate to reinvent the wheel if someone already has something.

Their requirements are pretty simple as far as I can tell and are as follows:

They will be driving a 3 phase brushless DC motor pulling a continuous duty of 8 amps, 10 starting amps. They want to be able to push 20-35 Volts DC in to the control circuit and send the same out to the motor. The motor is required to run at 900 RPMs and be reversible.

The current method of running the motor is through a control box that simply has a 24 Volt brushed motor that turns a three leg rotary switch at a constant speed. Because the control box was manufactured in the 1930s for the USAF it's nearly impossible to find parts for it.

All help is greatly appreciated, and if any information is needed on the current control box, or step motor just let me know. Thanks in advanced.

EDIT: Information on current controller.

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  • \$\begingroup\$ Can you give more information about the motor you're driving and the efficiency and/or control you want to achieve? Different kinds of motors require different feedback methods to properly control them. Some can be run "open loop" without any feedback but benefit from more intelligent control. From the sound of it, you want to build a state machine to drive 3 half H-bridges, but a modern strategy to do that requires some sort of low voltage supply. I think there's enough complexity in it that it'll justify introducing a low voltage supply or creating a new one. \$\endgroup\$ – Andrew Macrae Feb 13 at 2:25
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    \$\begingroup\$ Thank you for your quick response. I have added more information about the current control box. I am working on doing the same for the motor itself. \$\endgroup\$ – durbintl Feb 13 at 2:40
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    \$\begingroup\$ All information I have pertaining to the step motor has been added. Unfortunately... as far as the motor goes, in the 1930s the USAF was just throwing these things together and making them work. They weren't too concerned with efficiency. There are no Hall sensors on this motor. Just the three leads for each phase. I hope this answers your questions. \$\endgroup\$ – durbintl Feb 13 at 2:52
  • \$\begingroup\$ Looks like you have an interesting problem. It's probably a bit big for people to be making integrated parts to do the whole thing, you likely need to put together some reference designs for a few different pieces. I'd break the problem down to 3 parts: - 3 half H-Bridges preferably with integrated protection - a stepper motor sequence generator (it's pretty simple and ST seems to have made well-integrated silicon in the early '00s) - a power supply and a level shifter to power your sequencer and allow switching of the FET gates (this might be available as a dedicated gate drive IC) \$\endgroup\$ – Andrew Macrae Feb 13 at 5:42
  • \$\begingroup\$ This part almost does the sequencing and the power supply, but it doesn't look like it's rated for 35V: onsemi.com/pub/Collateral/MC33035-D.PDF \$\endgroup\$ – Andrew Macrae Feb 13 at 5:46

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