QuoteVDX ... here is the PCB-design of one of my "high-current"-drivers with +V and GND on the top/bottom layers - tested it with pulsing currents of up to 40 Amperes (limited by the PS) ... have to test for max. "safe" DC-current too: very cool (or... very hot... VDX ) how big's that board? (what area, cm^2)? how wide's the main power line at the start? i can see it's dropping down in staggby lkcl - RAMPS Electronics
Quotedc42 To achieve 18A bed current capacity on the Duets, we use 2oz copper and we duplicate the critical trace on the top and bottom of the board. 18 amps, that's a staggering amount. at 24 volt that's 430 watts. so you support Printbed MK2/3 using the 1.4 ohm connection normally reserved for 12v only. (24 * 24 / 1.4 ohm = 411 Watts) i might just be able to get 360 if i'm lucky.. 100W'sby lkcl - RAMPS Electronics
Quotedc42 Common practice on 2-layer boards is to make the bottom layer ground plane as far as possible, and to put power and most of the interconnect on the top. So there is no ground plane on the top, and no stitching vias - except for thermal vias used to cool surface-mount components such as mosfets and soldered-in motor drivers. interesting - and useful good practice to know. i haven't donby lkcl - RAMPS Electronics
Quotedc42 Too many through-hole parts and/or vias? Although the connectors for the Arduino and the stepsticks no doubt account for a lot of them. yehyeh. RAMPS 1.4 has something like 300 holes, if i recall correctly. what RAMPS 1.4 _doesn't_ have is significant numbers of GND bridging / shielding VIAs. absolutely none along along the edge of the PCB, absolutely none joining the power planes tby lkcl - RAMPS Electronics
i'm sort-of in... shock. this is a 4in x 3.25in board and it has 900 drill-holes in it! whaaat the ferrrr??by lkcl - RAMPS Electronics
ok so i decided to go with it - sent the BOM off to the factory and the gerbers - otherwise i will just keep on making tweaks. need to stop doing that and move on to other things...by lkcl - RAMPS Electronics
ok so yep i replaced the 100k and 10k resistors that were covered in black bits of gunk (crispy deep-fried solder paste...) and the stepper in position E0 works fine, now. the 100k resistor actually measured 33k and the 10k around 4.5k which tells you how much crud i'd managed to put on the PCB... whoops... so that's at 3.3v using the Due, which is a good sign.by lkcl - RAMPS Electronics
Quotedc42 The Duet WiFi design includes provision for that 10A inductor, but on production PCBs it is bypassed and not fitted. ahh interesting. turned out it wasn't needed? hmmm.. TMC2660s would not generate as much noise, would they... people with this design could be using DRV8825s and other low-cost stepper ICs...by lkcl - RAMPS Electronics
did a walk-through video: ran out of space on the sd card...by lkcl - RAMPS Electronics
ok so thank you to dc42 for mentioning about the EMI from the motors, i'd been looking at the duet wifi schematics and noticed that you have a 10A inductor on VMOT. i'd been wondering about that, whether i should put in some suppression filters or not, and the tangle of swiss-cheese spaghetti that this board has become just made me realise ferrite beads really are needed. so! this is what theby lkcl - RAMPS Electronics
Quoteobelisk79 I've found it interesting to follow the development. Like I said, once the design is relatively stable I'll be interesting in trying one out. My latest project has me swapping crystals on my MEGA2560 to get a little um oomph compared to the arduino reference design since the chips run 20% slower than what they are rated at. yyeah the allwinner a20 does that trick. variation in maby lkcl - RAMPS Electronics
Quoteo_lampe ..neverending story. I feel for you I hope the new chosen chip fits all the other needs too, like latency. But I'm sure it's quick enough. i hadn't checked... but now that you mention it i will... and ooo it's a good job you brought it up, as the datasheet says it only does up to 50mhz @ 3.3v and 5v. luckily there's no way the SPI interface is going to realistically get 50mhz, prby lkcl - RAMPS Electronics
Quotedc42 The 0.9V output low voltage of the Mega is probably quoted when the output is sinking a lot of current. It will be much closer to 0V when it is lightly loaded. AFAIR there are output voltage vs. sink current charts in the datasheet, and although they show typical rather than worst-case values, they should confirm this. ah ha! excellent, that was the clue i was looking for.... sectionby lkcl - RAMPS Electronics
SN74AVCT774 looks like a good candidate: uni-directional but *selectable* uni-directional... has 2 diferent supply voltages (like the TXS0104 range), so it would be ok to put 3.3v on the B side and either 3.3 or 5 on the A side... it would definitely do the job...by lkcl - RAMPS Electronics
oof! i just realised, the micro-sd card's buffer IC (using a SN74HCT125) isn't going to work. * power from the arduino/due can change between 3.3v and 5v * the microsd card can only take 3.3v * SN74HCT125 can only be supplied by 5V but its inputs (HIGH) can be signalled at 2V or above * SN74HC125 can be supplied by 2-6V but its inputs (HIGH) *MUST* be over 4.5V when it's supplied by a 5V railby lkcl - RAMPS Electronics
yyeah the resistors in positon E0 are measuring silly values. the 100k is registering 33k and the 10k about 4.8k. that's not a surprise: they were the first resistors i started putting on, used far too much solder paste and used the heat-gun as well (which i stopped doing very quickly) - it looks like not only the solder paste has created resistance but also the resistors themselves are damagedby lkcl - RAMPS Electronics
ok so with RepRapFirmware, i have: * Y and Z endstops working, no explanation as to why X isn't (despite it working on Marlin - i'll have to double-check that) * A4988 steppers working in positions X, Y, Z and E1. * A4988 stepper not working in position E0, worked in Marlin, will have to double-check (in case of a hardware fault or maybe the resistors need re-seating. the steppers are being driby lkcl - RAMPS Electronics
Quotedc42 If the Due is only supplying 2.95v output, then I suspect that either it is getting less than 3.3V supply, or you have a pulldown resistor with a rather low value connected to the output. A 74HCT chip is good to use as a level shifter to 5V. yehhh i didn't use a 74HCT, i used a 74HC by mistake. the datasheet says that they accept variable input from 2v to 6v, and their input responseby lkcl - RAMPS Electronics
arse! fek! that is an ecumenical matter! the SN74HC125 only switches on @ 3.15 volts for a 4.5v input, and the Due (ATSAM3X) supplies 2.95. frick! rrrr..... ok have to use a proper level shifter IC. frick. edit: arse, arse - it has to be a SN74AHCT125D or ACT type: those respond @ 2v (but have to be supplied with 5V, which is ok, that's what they're getting). what a pain in the neck.by lkcl - RAMPS Electronics
QuoteDust Those fuses looks suspiciously like wires But well done biig wires. yeh mike was in a rush (just before holidays) and couldn't find the fuses or fuse-holders. bit of a risk stuffing bits of wire in the holes instead, but hey...by lkcl - RAMPS Electronics
working assembled prototype! so that's 3 MOSFETs confirmed (fan, bed, extruder heater 1), thermistor 2, endstops, and 4 out of 6 steppers tested, two of them with TMC2100s and an A4988, the others with just an A4988. this is the version that can't do SPI, and only has 3 endstops. it's tested with Marlin-rc7 commit d97dc102, on both an italian and chinese ATMega 2560 r3. i'll set up the git reby lkcl - RAMPS Electronics
3 MOSFETs are working, yet to put thermistors on and test those. Marlin-rc firmware appears to be buggy: it won't enable the fan but by swapping Fan and Extruder (D8 / D9 to D9 / D8) i was at least able to check the hardware. four out of six steppers tested, all good. one i had to re-seat the resistors. i ended up putting on the TSSOP-14 buffer IC, it seems to be working well, it's a bit smaby lkcl - RAMPS Electronics
QuoteJustSumGuy I am going to lurk out here for a while... learning lots and have little to input thanx for letting me shoot some input tho I think I want one of these when it gets a little more traction.... you're more than welcome. (oh.... great book "good omens" by neil gaiman and terry pratchett... reminds me of the quote about bruce springsteen's "born to lurk"....)by lkcl - RAMPS Electronics
QuoteDust I also wonder if you can get SMD .1" connector strips... that would remove a bunch of holes Oh you can (not really surprising) only thing is, you gotta watch it on the ampage. THREE amps (!) and one of the things i'm doing on RD3D - bear in mind it's a 2-layer board - is connecting both sides and making sure there's plenty of copper leading to them. for the arduino pins.... yyeaby lkcl - RAMPS Electronics
QuoteDust Just a thought, I wonder if D1 would be better space wise as a SMD, and one of those cut able pcb jumpers... (two half circle with track between them, Im sure it has a name, but I don't know it) So it can be removed without heat.. yyeahh that's a good idea - i'm doing an stm32L471 arduino-clone, the atmega2560 reference design it's based on has a decent beefy SMT diode, i'll cut/pastby lkcl - RAMPS Electronics
ha! D8 through D11 work (no MOSFETs connected yet). stepper driver x works. pin-configuration is a pain: the pin-mappings are virtual (from the Arduino IDE) not physical (from the actual Arduino schematic). took me an hour going over the source to work that out: it doesn't help that the pins D0 to D15 are all identical in both the IDE and the Arduino Mega pin-numbering... anyway i'm using soby lkcl - RAMPS Electronics
QuoteDust the pcb needs some of sort of additive manufacturing technique vs the subtractive systems 3d printed/constructed fr-4 anyone? there are actually some companies that can do 3D-printed PCBs. i wouldn't bet on them being able to handle 10+ Amps though!by lkcl - RAMPS Electronics
ok so 30-40% done: components done, am on to the connectors. i'll leave off the MOSFETs, MicroSD and the buffer for now. i'm used to doing TSOP packages but after seeing how small it is i don't think it would be fair to other people considering doing this by hand, so i'll investigate if SOP-14 will actually fit on the board. for the MicroSD there's space, but for the MOSFETs it's going to be tby lkcl - RAMPS Electronics
Quoteobelisk79 Oh lord, that laptop board looks like a nightmare lol. I've done similar BGA's with a hand iron as well. Drag the pins and pray.. squash, squash... the laptop board was a lot of fun. first "real" major board i did myself completely (design, assembly). getting it into the available space.... yyeah, that one's awkward.by lkcl - RAMPS Electronics
Quoteobelisk79 Looks like fun times ahead, simple as I am, I rather enjoy a good soldering project. yehyeh, me too. Quote Ever do much SMT by hand? That's where it really gets interesting. nggggh yeahhhh i haaave.... four boards, took me... four months i think? it was one of the first PCBs i'd ever done myself, i went, "no way i can do this using a soldering iron, not comfortable with a heat-gby lkcl - RAMPS Electronics