Gen7 1.2 -> Heatbead Kills Firmware?

Hello Guy's,

i trying to builde my prusa mendel for 6 months now ... and is still not not finished ... and now next big Problem and i don't have a clue ... maybe somebody can help me:

I have a Gen7 1.2 Board (ATMEGA644) with Teacup Fimware (i couldn't get the Repetier firmware running, and im still testing)
I'M Using the Serial Port of an older Notebook and a RS232 - TTL Converter from Pollin with a max232 on it. (this part gets intressting later)

Now i got that far that i could manuall move all 3 axis with repetier host Software. That is working.
But now if i connect the heatbed and turn the heat on in the repetier host the Boad Stuck:
Heatbet and Extruder LED's start to blink.
If i turn of power supply (atx pc) and disconnect the heatbed and turn on again
it's the same: Heat1 and Heat2 Led's blink.
i cannt move any axis.

if i reupload the Firmware over serial connection i can move the axis again, and the blinking hase gone.
The bootloader seems to be still alive as firmware upload ist possible.

Now if i connect a 6 ohm Power Resistor to the Heatbed connecort i can turn on the output, and the resistor gets hot.
I can turn off, and on again. No Troubles.
The Heatbed itself has 1OHM. Is That ok?

Does Anybody have an idea on how to fix this? Is there a Problem with the Heatbed (to less resistance? or something with the electronics? Or Maybe just the Firmware? Or the PSU?


Another Funny thing is: If i Remove the ATMEGA and i Disconnect the Serial Connector of the Notebook, the steeper motors start to move slowly.
It seems to be a grouding problem: The RS232 - TTL Converter is connecte to the +5 and GND of the Gen7 board.
I Can disconnect RX/TX and +5 nothing happens. But i'v i remove GND Stepper Motors start to move.
This only Happens if no ATMega is present.
Don't know if this is a problem or normal behaviour ?

Thanks for Reading.
Stefan

Have you set your fuses to turn on the brown-out-detector? Without BOD, simply turning off the power supply can be sufficient to let the ATmega run havoc and reprogram its self.

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This only Happens if no ATMega is present.
Don't know if this is a problem or normal behaviour ?

Without the ATemga, a Gen7 board is just a bunch of disconnected tracks, ready to receive whatever radiation flys around


Regarding firmware I'd recommend to start with Teacup. It has fewer features, but also fewer options for misconfiguration (and guessing by the posts in this forum, fewer bugs).

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Hello Traumflug,

HI I've set the H-L and E fuse acording to the bootloader upload Secion in the wiki.
But i was using avr-studio since I'M on windows and i use the avr dragon.

is this ok?

could the voltage drop be the problem? Should i try a different (more powerfull) psu?

thanks for your reply
regards
Stefan

Look for bootloader upload and/or fuses settings on the newer wiki pages, like that for Gen7 v1.4.1. Early Gen7s suffered this BOD problem, too and I forgot when it was fixed.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

HI,

i just checked with a fuse calculator:
i programmed L-Fuse with 0xF7 as the wiki said.
But for brown i out i seems like a i would need a l-fuse 0xB7 ?

?

Hello I just checked Fuses and everything is ok.

Now i tried a different PSU. Yesterday i was using a "always on" PSU (with the ATX power on cabel shorted).

Now i'M using a normal PSU. And everytime i connect the heatbed eo either heater 1 or heater two
the psu turns off. Even if the heater is disabled.

Any ideas?

regards
Stefan

Your PSU likely needs a load on the 5V rail. Many PC PSUs have this requirement: [reprap.org]

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

HI just tried to put a 12v lamp on the 5v+ rail.

blub lights a little, but power suplly still turns off.

I've i use a 6ohm power restistor instead of the heatbed psu does not turn off?

any idea?

regards
Stefan

Quote

I've i use a 6ohm power restistor instead of the heatbed psu does not turn off?

Is this a question or a comment? It's possible to connect the extruder heater to the heated bed connector. If that works it looks like your PSU is overloaded when turning on the heated bed. To confirm you can connect the heated bed directly to the 12V rails of the PSU.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Hello Traumflug,

that was a comment. Looking at this, the board should basicly work.
and the PSU is maybe be the problem.

I will try to connect the heatbed directly to the PSU, simple but clever idea (hätt ich selbst dauf kommen können

Thanks for your reply.

regards
Stefan

Hello Traumflug,

i just tried to to connect the heatbed directly to the psu -> that is working.

I now change the Setup a littel -> now i'm only using the 4 Pin Molex connector. -> thte Power Supply is always on.

I now also locked the "application part of the ATMEGA Rom" with the Lockbit. -> now i do not lose the hole software after connecting the heatbed.

But i still doesnt work as is should: If i connect the heatbed either to heater one or two the AT Mega crashes.
In the repetier host Software i see serial com errors.

If the heater was turned on before connecting the heatbed it stay's on and the heatbed gets warm but the atmega isnt responding anymore. (cant send a commad)
Something is crashing the atmega, but i have no clue what?

any ideas?
regards
Stefan

Is it possible 5V supply voltage goes down when turning on the heated bet? If 5V SB goes below 4.3V, the brown out detector kicks in and resets the ATmega. Please measure the supply voltage of the ATmega. It's the pin left of the center in the row towards the serial connector: [reprap.org]

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Hello Traumflug,

i tried to use external 5V Voltage, suplied by batteries and a Voltage regulator.

That does not solve the problem.

Its very strange. If i connect the heatbed the board isnt controllable with the host software.

But if i leave the heatbed connected it the heater led turns on and the heatbed starts warming up.
an after alle the heater 1 led starts blinking ...
But i cant turn it off by the host software.

it seems to be related to the resitance of the heatbed (1 ohm) cause as is said before if i connect a 6ohm resistor it works.
Or the heatbed is causing some freaking interferences?

alltought this problem is driving me crazy, i would be very intressting to find the problem

regards
Stefan

Intressting fact:

If i connect heatbed -> heater turns on (led goes on, heatbed gets warm)

if i now REMOVE the hole ATMEGA -> heatbed still on ...

NOW i totaly confused.

regards

ok ...
If i connect heatbed to heater 2 -> heater 2 on -> remove at mega -> heater 2 led dims down a little
AND Heater 3 led turns on.

Now i connect heatbed to heater 3 -> heatbed gets warm -> heater 3 stays on -> even atmega is removed.

I cann turn the power suply off and on again (+5V led turns off) -> heater 3 still heating.
alltought atmega is still removed.

If i Meassure pin 40 of the atmega socket against ground i can see a little voltage wich is dropping fast -> after that
heater 3 led turns off.

Soooo the Problem seems to be realted so some capacity ? but i have no clue where this is maybe comming from ...

regards

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if i now REMOVE the hole ATMEGA -> heatbed still on ...

That's expected. If you remove the ATmega, the MOSFET input is unconnected and picks up random electromagnetic noise. There's no point in removing the ATmega.

And what is this "blinking"? When the firmware (BTW., which one are you using?) heats the bed and the bed reaches temperature, the heater ges on and off, but this can hardly be seen as "blinking".

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Hello,

i know that thers no real point in removing atmega but I'm expirementing to maybe stumble across a solution.
do you really think the "noise" could turn on the Transistor?
If i meassure pin 40 to ground i see 2 nano farrad.
And if i remove the ATmega -> heatbed is on -> i meassuere pin 40 to ground the heater turns off and stays off !
Can this 2nf cause the trouble?

regarding the blinking: the led's sometime really blink (half second on half second off) I'm using teacup.

BTW: I send you an e-mail regarding Gen7 Parts.

regards
Stefan

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regarding the blinking: the led's sometime really blink (half second on half second off) I'm using teacup.

Are you sure you've uploaded a firmware at all? The only really blinking stuff I'm aware of it SetupTest.pde, which helps setting up the serial connection but isn't helpful for much else.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY