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I might need a new Melzi

Posted by thewozza 
I might need a new Melzi
December 22, 2013 06:31PM
I have Nophead's kit.

I managed to break off the USB header, soldered it back on but now it is failing to be recognized by USB again. I just get "unable to enumerate USB device" no matter what cable, USB port or computer I use. This time I didn't rip it off, but it might be getting loose and I'm afraid that with my poor soldering skills it might not be repairable.

I'm going to try to re-solder it back on, but if I don't manage then what do I need to do to replace the board? I assume this is the same board that came with the kit:

Once I get this fixed again (whether by solder or a new board) I'm going to pin the USB cable to the frame so that there's no force pulling on the board.

Re: I might need a new Melzi
December 22, 2013 08:56PM
I thought I broke my Melzi 2 weeks ago, it's not fun soldering to that board....

Apparently you can connect using a serial connection....

Might be nice to figure it out and save some money...
Re: I might need a new Melzi
December 23, 2013 03:56AM
It turns out that the + on the micro USB header was loose. I was able to just heat up the pin with my soldering iron, and get it stuck on again.

I also did pin the USB cable in there with a zip tie, to attach this I drilled two holes in the dibond. I routed the cable from the melzi side, and around behind the dibond through the other loop of the zip-tie so now even if you yank on the USB cable it won't (hopefully) pull on the melzi at all.

But connect via serial? Isn't that what we're doing with USB? Or is there some other serial input?
Re: I might need a new Melzi
December 23, 2013 07:18AM
The USB connection uses internally on the board the TX0/RX0 pins of the ATmega. The ATmega provides a second UART interface, TX1/RX1 on the pin header connector JP16. It should not be too difficult to change the firmware for using the other UART. In this case, it can be used as a real RS232 connection (a voltage driver must then be added) or as an USB based virtual COM port (e. g. by an RS232-USB converter cable).

The problem may be, how the firmware change can be downloaded if the USB interface is damaged....

May be also, the alternative UART is already occupied with some other functionality, which conflicts.
Does somebody know about that?

I would like to use this UART for communication to a small microcontroller, which controls the temperature in the heated chamber of my M90
(attached photo, the candle type light bulbs are not due to christmas time, but for additional heating of the chamber;-). In this case I can use M commands for setting the chamber temperature instead of manual setting with a knob. At [reprap.org] already M141 is defined for that purpose, but I don't know if this function is implemented already in the Marlin version of Nophead in some way.
open | download - IMG_3760.jpg (113.7 KB)
Re: I might need a new Melzi
December 23, 2013 12:29PM
I think the TX1/RX1 pins are free to use provided you are not using a Panalolu2 or similar. I intend to try a direct connection to as Raspberry PI to leave the second USB port on the PI free and possibly get faster comms by eliminating the USB latency.

Not sure why you would add another micro controller for chamber control. You could just use one the free analogue ports to read the thermistor and connect another to a MOSFET to control the heater and then just add some code to Marlin rather than write it on another micro. I don't know if there is any support in later versions of Marlin but perhaps you could pretend it is a second extruder's heater, which does have support.

Edited 1 time(s). Last edit at 12/23/2013 01:22PM by nophead.

Re: I might need a new Melzi
December 24, 2013 03:02AM
gerdh, nice chamber!
could you give dimensions of the metal and plexiglas parts?
Re: I might need a new Melzi
December 25, 2013 06:47PM
The chamber is built on top of a 22mm MDF plate with 510mm x 510mm size. The cover is 540mm high and made from L-shaped aluminium profiles 15mm x 15mm, 1mm thick. The plexiglas is 4mm thick. The 540mm height is OK for filament spools up to 220mm diameter.

I reused the MDF plate from a former wooden chamber. But I doesn`t like it, because it gave very few insight, what happens inside while printing. So I replaced it by the plexiglas cover. For a new chamber I would choose a slightly larger ground plate.

The walls of the cover are mounted by M4 screws from the outside to the ground plate (photo 1, the screws go into threaded inserts in the MDF plate). So the cover can be removed for maintenance of the M90.

The top plate of the cover (photo 2) is sourrounded by aluminium profiles, which are not fixed by screws to the remaining cover. So it can be easily removed for access to the filament and to the extruder.

On the front and on the rear are hinged doors placed for access to the glas plate and the printed parts.

The heating is made by 230V light bulbs 2 x 46W, driven by a dimmer and controlled by a small PIC microcontroller, because I wanted to change as less as possible the original design of the electronics and firmware. The light bulbs alone achieve a temperature increase of about 12°C over ambient temperature. Together with the heat from the M90 the temperature inside the chamber can reach up to 50°C at 21°C ambient, depending on the heated bed temperature.
open | download - 1.jpg (395.6 KB)
open | download - 2.jpg (265.5 KB)
Re: I might need a new Melzi
January 11, 2014 04:07PM
I also broke the USB output from the board . Soldered new wiring .
Rang contacts, but nothing turns windows 8 and windows 7 43 will generate an error .
Can be a problem in the drivers?

How to check whether the chip melzi is work?

Light comes on(on board), but if you turn off all the devices that the light flashes. Reset button works too light goes off on Melzi , a few seconds later ignited .

There's a mini flash memory on it is a model for test printing but printing does not start. How start print from melzi board flash memory?

Traveltrousers writes, PS can be connected via RS232 ... how to do it ? Where can I get the pattern(drawing)?

How to check whether the chip melzi is work?

Sorry, my English not up to the mark/
Please help
Re: I might need a new Melzi
January 11, 2014 08:24PM
If you put a file called auto0.g on the SD card it should run it automatically.

There is a second serial port on the expansion connector. It is would need a TTL to RS232 convertor and firmware mod to use it. Google Melzi Schematic for a circuit diagram.

Re: I might need a new Melzi
January 12, 2014 02:40AM
RE: "put a file called auto0.g on the SD card it should run"

what found in the file auto0.g? (not file on google)
Maybe: auto0.g = somename.gcode???
after powering on Melzi - the fan is not spinning - board Melzi is dead?

thank you
Re: I might need a new Melzi
January 12, 2014 08:09AM
When Marlin starts it looks for a file called auto0.g on the Sd card. If it finds it it runs it. That allows you to build objects with no USB connection.

The fan not running on reset is not a good sign but there is no connection between the USB socket and the ATmega. Make sure you take off the auto reset jumper as that links the USB chip to the ATmega.

Re: I might need a new Melzi
January 12, 2014 08:37AM
I resolder usb port. windows sees the port as com № 3.
Melzi repetier connects via com № 3.
but no team work (or I do not know it work).
test: tried heat, try a fan tried to move on XYZ. but no movement.
repetier info writes all "OK". probably died fee(board) ...

All jumper is correct. But i test on all variants.
If the fan is not spinning board means dead?
Be careful with USB on Melzi!hot smiley

Now... Order new melzi fee(board).
In the new board "program is installed" or a need programming board?

thank you

Edited 1 time(s). Last edit at 01/12/2014 08:51AM by vitaly_l.
Re: I might need a new Melzi
January 12, 2014 11:24AM
If the board is replying with OK then the ATmega is working. Are you sure your 12V is connected?

The fan normally spins at start up. I am not sure why. It is either a bootstrap or a firmware bug.

Re-soldering the USB should not affect the rest of the board unless you splashed solder around.

A new board should have at least the boot strap loaded so you shouldn't need a programmer.

Re: I might need a new Melzi
January 12, 2014 12:10PM
RE: A new board should have at least the boot strap loaded so you shouldn't need a programmer.
melzi manufacturer said the same thing. It is the hope and joy! Thank you.

there is an option that the board was originally broken on the way to me.
When I first started printer, the fan does not rotate and the USB port was still intact.

here a good description of repair USB [forums.reprap.org]

I read about the fan. It must be twisted and you confirm it too. So dress exactly broken. It's a shame but not fatal.
Good that you are familiar with this board, because in my country all benefit RAMP 1.4 and ask there was nobody.

On this adress LSD connect, example: [forums.reprap.org]
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