This page is the checklist for GenBoard/VerThree with stepper driver chip
- the stepper driver chip is the only throughole chip on the board. It's called powerdip footprint: the 2x2 middle pins (GND5) are used for cooling. The SN754410NE chip is mounted in natural orientation, the notch is away from EC18. If you don't have this chip, the rest of the checklist is not interesting (but the stepper lines will not be activated of course)
- 10uF (1210 size, 35V) capacitor is recommended under the stepper chip, on the bottom side (see GenBoard/VerThree/RescueKit, namely rescue2 envelope for the cap)
D45 options
The "D45 southern pad" (referred below) is at the board-edge, 70mm from the left side. This goes to the 12V supply pin of the stepper-driver chip.
EC36-pin25 (corner pin of EC36, closest to the PCB edge, and closest the EC18) is the 12V mains supply. The advantage of using this pin (below) instead of the "northern pad of D45" is that the stepper current is drawn directly from the EC36 supply pin, and not going through the small fuse. Therefore the small fuse can be really small (eg. 450mA) providing really effective protection.
Chose one of the 3 according to your taste:
- wire from EC36-pin25 to southern pad of D45 - if the wire is not a fuse (not the weakest link, thus never blown), reverse diode (detailed in next option) is not needed.
- fuse and reverse diode - this is the most sophisticated option:
- 2..5A fuse (2A limit is enough normally, as bipolar stepper never draws same direction current from all 4 channels) from EC36-pin25 to "D45 southern pad". This can be a thin wire, acting like a fuse (if you know how thin it should be). Practically, apply this at the bottom of the board. Solder it after (or at the same time as) the diode (below), practically to the diode pads.
- 1n4007 diode: cathode (- mark) at EC36-pin25, anode at "D45 southern pad". Practically, apply this at the bottom of the board. This is effectively a flyback diode, provides some protection should the above fuse be blown.
- wire in place of D45 - works fine if the F1 fuse is powerful enough not to be blown from the stepper current. Note that with this wire it does not matter if there is a diode in D45 pads (with any orientation). A wire parallel with the diode (shorting the diode pads) makes the diode redundant. Leave this if you already have it, but choose one of the above for new installs.
Question ::
Sombody has a picture off how this is done for better understanding?