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RAMPS 1.4.2 fork: RD3D v1.0 (6 steppers, 24v, Due)

Posted by lkcl 
Re: RAMPS 1.4.2 fork: RD3D v1.0 (6 steppers, 24v, Due)
October 30, 2017 04:16AM
Quote
obelisk79
That is a lot of holes. Wow! It's one thing to see in the files, another entirely too see them on a physical board.

tell me about it. it's why i want to split this board into upright daughtercards (like the old PCs from the 1970s / 80s), even for the MOSFETs. that way people can pick 2-MOSFET boards, 3 MOSFET boards, different power levels etc. so, i'll put 3 headers on the left side with 3 pins each (they have to come off of D3-D12 with D13 being power-enable as well as LED), with I2C (and possibly SPI) running to them as well. another header on the left side for DCin. then 4 14-pin expansion headers spaced near-equally top-to-bottom for steppers.

i worked out that it's just possible to fit 3 steppers onto one of those 14-pin expansion boards, if you use two sets of STEP/DIR and use I2C to communicate with an STM8 which controls the EN# of the stepper ICs. so i could do 2-stepper and 3-stepper boards, potentially for a total of *twelve* steppers, which actually starts to run into problems with RepRapFirmware as it uses a 32-bit number to store the stepper status in order to get as fast simultaneous control over all steppers as possible.

the nice thing about splitting all that out is, you now don't need heavy power-handlng on the main PCB *at all*, all the daughter cards take their own independent power, you could do a solid-state relay board as well (for 110/240v mains style silicon heaters and so on). and unlike BAM & DICE, right-angle 2.54mm pin-headers are a lot cheaper than 52-pin PCIe connectors.
Re: RAMPS 1.4.2 fork: RD3D v1.0 (6 steppers, 24v, Due)
October 30, 2017 06:01PM
ok so that's all the ICs (except the EEPROM, why the heck is that needed anyway??), resistors and capacitors, plus the inductors, MicroSD, power connector and fuses.

if i put on the 3-pin 5/3.3->VCC connector on i can test it powering up an arduino, then try some things like switch on MOSFETs (without MOSFETs) and confirm that the SN74LVC125 is working, and so on.

i've made absolute minimal usage of the hot-air gun, here. bit 100uF capacitors and the MC7808, that was all. the last experience i had using it on the 0805s was it really failed to do a decent job, i had to do more recovery than actual soldering.

hand-soldering of 0805s seems to be straightforward, with the exception of when one end is on a GND plane. those actually sink so much heat that the soldering iron (set to 400C) actually starts to stick to the PCB. amazing. but also a good sign, as far as connectivity is concerned. this is presumably primarily what "thermals" are for... but i entirely switched generating those off, right across the entire board.


Re: RAMPS 1.4.2 fork: RD3D v1.0 (6 steppers, 24v, Due)
October 31, 2017 04:19AM
I use hot air for reworking boards, but for initial assembly of an SMD board I find a soldering iron or a hotplate easier.


Delta printer calibration calculator, mini IR Z probe, and colour touch screen control panel: [escher3d.com]

Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
Re: RAMPS 1.4.2 fork: RD3D v1.0 (6 steppers, 24v, Due)
November 01, 2017 03:46AM
ok so SN74LV125 for the MOSFETs is working. managed to smoke an 0805 capacitor.....
Re: RAMPS 1.4.2 fork: RD3D v1.0 (6 steppers, 24v, Due)
November 01, 2017 01:45PM
young kids of today, will smoke anything! tongue sticking out smiley
Re: RAMPS 1.4.2 fork: RD3D v1.0 (6 steppers, 24v, Due)
November 02, 2017 12:47AM
i really should have paid attention to the fact that one of the 0.1uF capacitors went up in smoke and produced a small flame. the one that i put on the main power rail also decided to go up, this time because it had the full power of the PSU (350 watts) behind it, and it was also right next to the fuse, the fuse plastic caught fire and it's badly damaged the copper tracks on *both* sides of the PCB.

thinking about it: i ordered just "0.1uF capacitors". they're quite likely to only be 6.3v or 10v, they almost certainly won't be ceramic, or X5R or X7R temperature-rated. so... putting 12v through them, with the full power of a 350 watt PSU behind them and no fricking wonder they got hot enough to catch fire.

so.... hum... yyehhh... i can't take *this* board to SZMF! i think i have some X7R 0.1uF 50V capacitors here.

[edit] damnit, taking out the charred remains of the 0805 capacitor, the fire was intense enough to burn several millimetres through the FR4 PCB, and it's also shorted out the 12v and GND copper. i'll have to recover some of the components and start again. ho hum. this time not putting on 6.3v capacitors where it's going to be supplied by 12 to 24v, eh?



Edited 1 time(s). Last edit at 11/02/2017 01:14AM by lkcl.
Re: RAMPS 1.4.2 fork: RD3D v1.0 (6 steppers, 24v, Due)
November 02, 2017 01:12AM
Can't make an omelette without cracking a few eggs right?
Re: RAMPS 1.4.2 fork: RD3D v1.0 (6 steppers, 24v, Due)
November 02, 2017 01:28AM
Quote
obelisk79
Can't make an omelette without cracking a few eggs right?

*sigh*... apparently not smiling smiley i may be able to recover some of the components from this board, but after the experience of messing up due to re-soldering some of the connectors i'm inclined to just chuck this board and start completely again. nggggh! 2 days gone! and i'm leaving for SZMF on the 5th!
Re: RAMPS 1.4.2 fork: RD3D v1.0 (6 steppers, 24v, Due)
November 03, 2017 08:20AM
okaay so the next one, much better (this is with an atmega2560) a few quirks, the capacitors and on-board (ATMEGA) pullups work well but previously i was used to no pullups, had to work out the endstop configuration: all good now. 4 of the steppers are working great, i had messed up with the names of the NETs so had X and E0 DIR and STEP reversed... doh. 4 large MOSFETs all good: reduced the indicator resistors to 4.7k as 1.8k was horrendously bright. heated bed works great, thermistors work great.

so as i'm short on time i've moved on to the TMC2660 expansion board, i've assembled one and am going to fire it up tomorrow (and take photos). i'm not connecting the SPI signals for the first test, i'm just going to rely on "default" settings and see what happens. if it doesn't go "pop" i'll be happy.

i'll need to take a closer look at marlin-rc source as apparently it does actually already have support for TMC2660 which would be fantastic, but using SPI so that involves a bit more investigating.
Re: RAMPS 1.4.2 fork: RD3D v1.0 (6 steppers, 24v, Due)
November 06, 2017 06:36AM
Hope you managed to get everything working in time! Let us know how it goes.
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