Ardoino mega shield problem on Prusa I3

Dear friends,

I bought a full unassembled prusa mendel i3 set 2 months ago. I assembled everything correctly. Then, I tried everything by using Pronterface.. There were no problem. Every motor was working. Heat bed and hotend was heating without problem.

Attached you can see a photo of my arduino mega shield.

At that time, I did not have plastic. Then I stopped dealing with printer and ordered an ABS stock from China. After nearly one month, ABS has came.

Then I wanted to try ABS printing. Unexpectedly, heat bed was not heating. Other than that, everything was working.

I did not understand the reason. Because It was working one month ago. During one month, I (and nobody) did not change anything. Even nobody touched my printer.

In order to understand the problem, I switched power cables (D8 and D10) of heat bed and hotend. This time hotend was not heating but heat bed was heating. I understood that heat bed has no problem.

Then I reswitched the cables of hotend and heat bed to original. Power was off. Then I made this try one by one:

1-Power on of my ATX Power
2-Read the voltage at arduino mega shield power input. The two inputs were 12 V. There is no problem.
3-At pronterface, I started heat bed heating. During this start, I measured the voltage at power inputs (only 11A+) of the arduino mega shield. It suddenly dropped to 0 V.
4-At pronterface, I stopped heat bed heating. After that, I measured the voltage at power inputs (only 11A+) of the arduino mega shield. It increased gradually. It took nearly 15 minutes to increase to 12 V.

- During all these tests, I looked whether any component on the arduino shield was heating unexpectedly. But, nothing was heating extraordinarily.

- Also I looked at the resistance of those big yellow (or green) resistors. Both were nearly 0.8 ohm

What do you think the problem is? Please help..

Thanks in advance

Best regards..

I've seen issues with ATX PSUs where they don't like spikes in power demand on the 12v when there is little or no load on the 5v output.

I guess this depends on your ATX PSU, but one thing you could try is putting a constant load of several amps on the 5v output.

Try to find a load for the 5v output of the PSU of a few amps. I've used a 12v lamp, but connecting to it was not easy as you can't solder to the domestic lamps with the small pins on the back. So if you are near some form of electronics store, the better solution may be to get a high wattage resistor e.g. 5 ohms or lower.

However this of course may not be the problem, but it does sound like the PSU is shutting down.

Or get another PSU, a lot of people use the cheap LED driver PSUs but they are supposed to be a bit unreliable.

Or get a more expensive industrial 12v PSU.

Dear rogerclark ,
First of all, thanks for the response.. My power supply is Everest 400W with code EPS-1660C
The picture of its specifications is attached.

Maybe the problem is with PSU.. But I need to say:

- At first, everything was working great at the same time. 5 motors were working, Heatbed and hotend were heating... All are working at the same time... So if power supply was not good, then it should have made the same problem at first. Am I right?

- Also, I think my PSU is not bad type.

Do you still think PSU may be the problem?

Best regards

Fatih

I am a Newbie, but familiar with electronics. Could others comment on these suggestions as I don't want to get off on the wrong foot !
To load your 12v supply try using old car/motorcycle headlamp bulbs, you can usually solder these. You can also use them to load the 5v supply, but will need more than one bulb. If you have a PC using the same psu type you could try swapping them to test for reliability. Take care, you don't want a broken PC as well !

Quote
fatihaltunel
Dear friends,

In order to understand the problem, I switched power cables (D8 and D10) of heat bed and hotend. This time hotend was not heating but heat bed was heating. I understood that heat bed has no problem.

This suggests a problem with the D8 output.

Quote

1-Power on of my ATX Power
2-Read the voltage at arduino mega shield power input. The two inputs were 12 V. There is no problem.
3-At pronterface, I started heat bed heating. During this start, I measured the voltage at power inputs (only 11A+) of the arduino mega shield. It suddenly dropped to 0 V.
4-At pronterface, I stopped heat bed heating. After that, I measured the voltage at power inputs (only 11A+) of the arduino mega shield. It increased gradually. It took nearly 15 minutes to increase to 12 V.

This is inconsistent with your first test result. There might be a loose connection to the plug going to the +11A input. These wires need to be large since it has to carry 11A to power the bed.

Did you measure the voltage across both D8 terminals? The MOSFET turns the power to the bed on and off on the ground wire. That means that the +D8 terminal should always read +12. relative to ground. And the -D8 terminal will read near 0V when the MOSFET grounds it to turn the heater on and near +12V when the heater is off.

Quote

- Also I looked at the resistance of those big yellow (or green) resistors. Both were nearly 0.8 ohm
.

Those are fuses. They should have very low resistance. Your measurement is a bit high since it includes resistance of the multimeter leads. Your fuses look frine.

Quote
bri857
I am a Newbie, but familiar with electronics. Could others comment on these suggestions as I don't want to get off on the wrong foot !
To load your 12v supply try using old car/motorcycle headlamp bulbs, you can usually solder these. You can also use them to load the 5v supply, but will need more than one bulb. If you have a PC using the same psu type you could try swapping them to test for reliability. Take care, you don't want a broken PC as well !

My experience with two ATX power supplies is that they won't turn on unless there is sufficient load on any rail (+12V or +5V). Without a load on the +5V leg, I couldn't turn on the power supply as long as a heater or the motors are enabled. As soon as all the heaters are off and the motors are on idle, the ATX supplies would turn off. Putting a 10 ohm load on the +5V rail fixed this issue. It might have also increased the +12V output but not by much.

Dear friends,
FYI...The problem is from power source as you said. It is shutting down the power because of high power.

I suggest you try the IRC channel for some realtime help.

Dear brnrd,
Actually first I tried IRC channel, 2 friends tried to help but some time later they disconnected.
Also, I think this forum is good to talk. Because people will have opportunity to search whether there is similar problem.

Best regards

Fatih