Testing deficient Melzi Ardentissimo

HI,

I've got a Melzi Ardentissimo for an Huxley here, and the Y-MOTOR potentiometer doesn't have any power.

When I connect it to USB in USB powered mode, the led keep blinking.

I have wired X,Y,E and Z-MOTOR only.
Pronterface seems to work but I can't get the GET POS button displayed.

I can connect to it with Pronterface, but it won't answer to M503:

Connecting...
start
Printer is now online.
SD init fail
>>>M503
SENDING:M503
EC:1
, Hotendok

Here's the answer to M114:

>>>M114
SENDING:M114
X:0.00Y:0.00Z:0.00E:0.00
EC:1
, Hotendok

It doesn't move on anything like G1 X5 F500.

Is the board supposed to answer move orders with only MOTOR wired?

What other test can I run to check it?

cheers

I think you may need a hot end thermistor wired in as well, or the firmware detects an error condition.

You can do this by wiring the thermistor directly into the board, by bending the wire legs and putting them in the appropriate terminals on the board directly. It will then read the room temperature, so you don't have to build the entire hot end before testing the board.

cheers, that was it.

At least now, the led is continuously lighted. It goes off briefly when I connect to it with Pronterface and goes on again, for good.

I get the room temperature with the Hotend thermistor, pretty nice.

However I still can't get any answer form the board with M503 or M114 or G1 X5 F500.

I can't get the custom buttons (GET TEMP, GET POS, ..)to appear in Pronterface, but I don't suppose it should influence the communication.

Is there anything else that MUST be connected to the board to get it answer commands, or can I already assume there's something wrong?

A blinking LED is not necessarily bad news and is built into the RRP firmware. (I assume you are running a RRP Huxley). From memory, it blinks when the hot end is heating up.
Alan

coolnodje Wrote:
-------------------------------------------------------
> cheers, that was it.
>
> At least now, the led is continuously lighted. It
> goes off briefly when I connect to it with
> Pronterface and goes on again, for good.
>
> I get the room temperature with the Hotend
> thermistor, pretty nice.
>
> However I still can't get any answer form the
> board with M503 or M114 or G1 X5 F500.

You said previously that M114 gave the following response:
>>>M114
SENDING:M114
X:0.00Y:0.00Z:0.00E:0.00
EC:1
, Hotendok

That is a correct response from that command. It also tells me you have very old firmware, so M503 is not implemented. In fact, I suspect you have such an old Melzi that the micro-controller is an Atmega644 running Sprinter firmware.

>
> I can't get the custom buttons (GET TEMP, GET POS,
> ..)to appear in Pronterface, but I don't suppose
> it should influence the communication.

Not having those will indeed not affect the communications. You can create them yourself by right clicking where they should be, and creating them from scratch. Alternatively, you need to copy the .pronsolerc to your home folder.

>
> Is there anything else that MUST be connected to
> the board to get it answer commands, or can I
> already assume there's something wrong?

Try connecting to the board using a serial terminal, such as Cutecom or Putty, and see what error messages (if any) the board is reporting.

You said

> When I connect it to USB in USB powered mode, the led keep blinking.
>
> I have wired X,Y,E and Z-MOTOR only.
> Pronterface seems to work but I can't get the GET POS button displayed.

Have you attached a 12v power supply to the power header of the Melzi? (Actually, the Huxley is designed to work with a 19v power supply, but 12v will do.) The 'USB powered mode' only powers the main chip on the board, and things like the thermistors and endstops. It won't power the motors, heated bed or hot end, these need 12v and a few amps as a minimum; USB only supplies 5v and 500 milliamperes.
See this page for correct wiring. [www.reprap.org]

OK, sorry for being such a noob, I was testing while USB powered.
I just blindly followed RRP commissioning part...

Basically, everything is working as expected.
I'm just really surprised that I can get the Y-MOTOR to move even though its voltage control potentiometer is measuring 0V.
and then I have no idea to how much it is set.

the kit provider says the Z & E motors have to be set to 0.6V since the E is a bigger stepper and Z goes with 2 motors.
The power supply provided gives 24V ( ajusted down to the min 22V by myself).

It's at odds with what RRP Huxley wiring page indicates, but it seems to work.
The 2 Z-motors get pretty hot though compared with the other motors which stay cold.

jmgiacalone, you guessed right, I have a Melzi with an Atmega644. I don't know about the firmware though.
What are the potential problems/limitations that go with using such an old board ?

I have a .pronsolerc file right in my home folder with the proper config that indicates slic3r where to find a config.ini.
I found it very buggy to save to the config.ini with Slic3r, I'm under Os X latest...

Ah, right, so you didn't get this from RepRapPro? Have you asked these questions from the company that provided the kit? Where's it from?

The power supply should be fine at 24V for the motors, all a higher voltage does is energise the coils quicker, which is actually a good thing. The stepper drivers can cope with up to 36V I think, and control the current (amps) to the motors. RepRapPro recommend 1 amp maximum for NEMA14 motors, which is 0.4V when setting the stepper driver potentiometer. For NEMA17 motors you can go a bit higher, up to say 0.6V (1.5 amps), but I wouldn't go higher than this, firstly because it will make the motors run hot, as you've already found out, and secondly because you shouldn't actually need that much torque - if you do, there is something restricting the movement of the axes. Most repraps are limited to 1amp due to the use of Pololus and their poor heat dissipation, and cope fine.

If you wire the Z axis motors in series rather than in parallel (as explained in the Huxley wiring, and is a better way to wire them) you won't need to turn up the stepper driver. I'd also turn down the E stepper to 0.4V, and only turn it up a little at a time if it skips.

You may have a dodgy pot on the Y axis, if you're reading 0V from the centre of the pot. Try reading the voltage from the soldered joint contact in front of the pot, on the side where there is only one (that's the output side of the pot). Alternatively, you'll have to measure the current going to one of the coils by putting an ammeter in line with one of the coils of the motor, and moving the axis very slowly until you can read a peak current for that coil. I think that will be 70% of the current the motor receives.

One problem of using high voltage power supplies is correct choice of hot end resistor, and heated bed. I don't know off-hand, but you'll want check that you have been supplied with a suitable hot end resistor, as those specified for 12V may be operating outside a safe envelope when run at 24V, or just never get that hot (I can't remember which way around it is!). For example, RepRapPro use a 2.7ohm resistor on the hot end for the Mendel @ 12V, but a 6.8ohm resistor on a Huxley @ 19V. This gives the right amount of power for heating the hot end, depending on the voltage.

The only limitation of using a Atmega644 version of the board is a limit on the memory for uploading firmware. You can use the latest firmware, but you will have to remove features such as the eeprom settings saving (that's what M503 does, and why it doesn't do anything for you - it's not in your firmware!). You should be able to have most other things enabled, ie SD support.

Sorry, can't help with your setting problems - I have no idea where config files are saved.

droftarts, thank you very much for your time, your detailed explanation is very helpful!

I don't really get what you mean by

Quote

You can use the latest firmware, but you will have to remove features such as the eeprom settings saving

but from what you say I figure I can go on safely with the Atmega644.

I got the kit form a local guy here in China. It was very cheap, but also very incomplete and without any explanation as for what differs from the original RRP.

All in all not too bad considering, but it was a lot of hassle to figure out details as it's my first Reprap, and I've never even seen one working.

I'm close to get it working, I expect I'll have to iron out runtime problems now.

thanks again.

I have one more problem with my Melzi version: the heated bed MOSFET connector isn't installed.

According to RRP wiring step, the MOSFET controller is supposed to be connected to a pin on the expansion header (top row, second pin in from the left), as shown on the picture:

I haven't got that expansion header on my board, I could wire one though, but this top row second from the left pin doesn't seem connected to anything, neither on the board, nor on the model

See http://www.reprap.org/mediawiki/images/a/a3/Melzi-ardentissimo-top.jpg for the entire pic of the board

--------------------------------

It is connected on the back of the board, I just happen to miss the expansion header.

Edited 3 time(s). Last edit at 02/10/2013 11:35PM by coolnodje.

That pin should be connected by a track on the bottom of the PCB.

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