Harvey is yet another reprap electronics / reprap controller Board. It is built around a STM32F102 Cortex M3 and uses Sanyo LV8549M Stepper Drivers, everything on one small PCB.
Beware, this has not yet been assembled and tested. If anyone feels like checking the design, please do so. In #reprap I'm gnurbs, jabber mesages go to [email protected]
This Board was designed by ari, with his personal design conceptions: SMD-Parts where available, single sided, very compact single PCB. In fact it is so small, it will need a Heat spreader for the stepper drivers. Ari finds SMD-parts more convenient, especially if one produces the pcb oneself - less drilling.
Logic power (+3.3V) is supplied by USB, Power (VDD) by a 5.5/2.5 mm Jack. 8-16V are allowed, the actual voltage is measured by the µC. One of the IBM-thinkpad laptop power supplies should do. In the last sentence put emphasis on IBM as in not Lenovo. Those are 16V and have a fitting jack.
This Board features an STM32F102 microcontroller. relevant for this Board:
- 48 MHz Cortex M3 core
- builtin USB
- 2 Timers with 4 PWM channels each
- 12-bit ADC
Pprog is the programming header. You can flash the µC over USART1 when BOOT0 is asserted during reset. These plus USART1s clock are on the header. I think you could also use this as a second SPI
This header is intended for future extension. It has all the unsused pins of the STM32, with several interfaces available:
- _maybe_ TIM2_CH2
maybe a board with lcd, sd-slot and some buttons would be nice to have as an expansion :D Ethernet, too
I just thought I connected two pairs of stepper to the same PWM channel, so I'm listing all of them here B:=TIM2_CH, C:=TIM3_CH
just updated the schematics to B1-ePWM, B2-bPWM, but this will need nontrivial updating in the layout. Maybe it will be better to instead C3-yEn, C4-zen
Stepper Drivers are Sanyo LV8549M which are pretty dumb but require no external parts. They are not much more than two H-bridges that are controlled by two pins setting the pase and one enable. They cannot do microstepping on their own, but doing this by hand should be possible. They have an enable-pin that is said to accept PWM for current setting, but the datasheet gives no details. They are wired to PWM-channels of the µC anyway.
Two PWM channels are wired to FETs (IRLML6344TRPbF with 29 mOhm R_ds(on), spec'ed to 1.3A, that gives 20W on each teater - that's a little little. However, they are also spec'ed to 0.8 W Power dissipation, which makes me think 4A could also be possible. Thinking about this, one should propably use other connectors for the heaters.
- check if all pins on the expansion Header are 5V-tolerant.
maybe +3.3, VDD and status LED would be nice.