Using my M12 DCMotor driver as base I want to upgrade this board as described below – running motors are fun and this board is capable 10A (actually 2 x 10A) at 24V, so it is quite powerfully.
This board is very capable as each driver privide two separate half H-Bridge circuits with current sensors at 5A each. I think I can drive a 10A 3-phase from this, but I can drive 4 solenoids, 2 DC motors or a larger Stepper motor. For now I will just build and code this in the M12 format, but I am starting to plan a simpler version to drive cost down.
- The first change is that the connector on left is a fast TTL UART. I would like to replace that with something that enables the module to be used stand-alone and still be used as a module in a system. The answer is CAN, RS485 or RS232, but I need to research a bit on cost, speed and space usage. I also want to evaluate changing that micro connetor to terminals. One of the signals is an enable signal that switch on/off the PSU, so I need a jumper for that to be used in stand-alone mode.
- MCU used here is STM32G491Cx and I will replace it with STM32H503Cx due to cost. H503 is M33 at 250Mhz and contains 128Kb Flash and 32Kb SRAM, but it has a very nice bootloader in ROM so the 128Kb Flash is for application only – and 128Kb is quite a lot as long as you don’t drag in Ethernet or similar.
- The SPI Flash is great in SO8 format, but I have changed to a even smaller footprint to save space – and space is an issue on this design. One argument is also that I might be better off with a FRAM/EEPROM in this case since this is a motor controller.
- The SWD connector at bottom left will be replaced with my old SWD connector.
- Current sensor in middle bottom will be removed and replaced with 4 x current sensors on the DRV8873. This put the galvanic isolation layer in question as it is very difficult to have an analogue signal to cross galvanic isolation . it is possible, but I need to evaluate what I do here. DRV8873 is not isolated themselves, so it might be an overkill to have this isolation barrier + I could maybe add an isolation barrier on the connector at left.
- The big 24 to 5V DC/DC is not needed – firstly I can replace it with a smaller SMD DC/DC from RECON, but secondly it serves no purpose if I remove the isolation layer.
- 24V connector needs to be evaluated – swap it for a terminal and maybe feed 5V from this to reduce power to 1 connector.
- The final change is to replace M12 with a terminal block due to cost.
- One major issue as I designed this was size – this board is 25 x 70mm, but without the M12 design I can use whatever size I want.