So i'm building a 3d printer based on a ramps 1.4 and when testing, i noticed that whenever i power the a7 pin the a2 pin on the mega 2560 also gets power which causes one of the stepper drivers to shut down as long as one of the two pins are powered. When i tried sending current between the two pins (i know who does that lol) the green ON indicator LED on the board lit up which is weird. Does the problem sound familiar to anyone? Will it go away if i solder out the LED? Is the board a defective unit or is it a fake? Any help is appreciated
Welcome to the forum.
Is it an official Arduino board ?
To check the board, remove everything from it. Then use a multimeter to check for shortcuts. Perhaps a magnifier might help to see shortcuts by solder blobs.
No, it does not sound familiar. Sometimes a cheap clone has missing copper traces, or a shortcut at the header (two pins next to each other), or is very sensitive for electronic noise.
If you can make detailed scans of both sides, then maybe we can spot something.
It's not clear to me what you mean by "power the A7 pin". On the RAMPS board, Pin A7 is connected to the "Direction" pin of the Y stepper driver (Y_DIR). The A2 pin is connected to the "Enable" pin of the Y stepper driver (Y_EN).
What do you mean by "sending current between the two pins"?
On the Arduino MEGA board? The RAMPS 1.4 board? One of the tepper driver boards?
Alright so basically every time A7 which is the direction pin for Y axis, as you said, goes HIGH, the A2 pin also shows voltage (but less) for some reason so voltage is sent to the enable pin on the driver which ultimately shuts down the driver and the motor with it so every time the control board wants to turn the motor in the direction which requires the DIR pin to go high, it just shuts down the driver because the enable pin, which should normally only get voltage from the A2 pin also gets power through this short that i've been talking about and i've confirmed this with a multimeter. Every time DIR gets 5 volts, EN also gets some voltage, less than 5 but enough to shut down the driver and as soon as i connect EN to a ground, it works normal again however this is obviously not a good solution because i won't be able to disconnect the motor and it'll be powered all the time which can't be good.
With a multimeter i checked the pins and A2 and A7 are connected. When you send 5v through them with the board off, it lights up the green LED which normally indicates the board is on. I have no idea how but they are connected together for some reason. My guess is if i desolder the LED it might fix my problem. Has this ever happened to anyone? Can you maybe check this with another mega 2560? Because i'm pretty sure this is not supposed to happen lol. It could be a fake board but i paid for an original one so it sucks.
Are you sure that you removed everything from the Mega board and that you can hold your Mega board in your hand with nothing else connected ?
I looked at the PCB of the official Arduino board, but the traces for pin A2 and A7 do not come near each other. Your ATmega2560 chip could be broken.
Removing the led would not solve something. Please don't remove it.
Can you make a photo and point to the led ? We don't know which led it is.
It sounds like a floating pin on A2. You probably need to tie A2 high to default off, and specifically write a2 low to enable the driver
Hi
Thanks for the reply
Yes i am pretty sure i've removed everything.
How can i check my chip? Is there a code i can run to test it? I'm pretty sure it's ok because it can run marlin and i can use a display with it no problem. I doubt a broken chip can do that. Maybe it's faulty from the factory or something like that but i don't think i've broken it, well i hope so...
According to your first message i checked all the traces and found no soldering shortages or anything obvious in the copper. Here's a photo of the board. Please feel free to check for its genuineness and let me know. The LED is also marked.
Hi
Thanks for the reply
I don't think that'll fix the issue. The marlin firmware already has that. The default is that the EN pin gets 5v until you start a g code or you ask the steppers to move or home, then the EN pins become LOW.
I think that is a official Arduino board, just a older version.
The "ON" led turns on when the board is powered.
If the board is not powered and a voltage is applied to the input/output pins, then that led will also turn on. Try to avoid that, because something might get damaged.
If A2 is shortcut to A7, then the chip is damaged.
The A2 being shortcut to A7 without those being shortcut to GND or 5V is not normal. I doubt if you have measured that correctly. It is even possible that the Mega board is okay.
If you buy another Mega board, then you could make the same mistake with the same result.
Oh great because i was pretty bummed to find out it's a clone.
I've moved the previous A2 pin function to another pin and everything is working seemingly without any issues now. Thanks very much for the input. It's still very weird to me that this happened. I'll make sure to keep you posted if i found anything worth sharing.
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