Marlin + RAMPS 1.4, spinning motors?

Hello! I am very new to RepRap and am trying to implement the Marlin 1.0 firmware in a personal project which mimics a 3D printer, except that it uses an airbrush to make art. I have a Sainsmart RAMPS 1.4 board atop a Mega 2560, with a single stepper driver plugged into the X axis. As I will not be using an extruder nor a heatbed I have neither plugged in. Additionally I have a Smart LCD Controller (with rotary encoder). The latter works correctly.

However, when I attempt to move the the motor that is plugged in, with stepper motor plugged in, nothing happens- the motor doesn't act at all. Additionally, a thermistor reading on the LCD controller is coming up as 498-500 degrees despite the fact that nothing is plugged in there (as my project will not need it.) Can anyone lend a bit of advice as to how to get at least as far as the "spinning motors" stage? Thanks in advance =)

If you have nothing plugged in the thermistors connector, the firmware "reads" a very unusual temperature and throws an error and stops working. Put the thermistors there and it will read room temperature, or put a resistor like 100k to 10k in its place so it will "read" some temperature at which it will work.

Two threads down its the same issue

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NoobMan
If you have nothing plugged in the thermistors connector, the firmware "reads" a very unusual temperature and throws an error and stops working. Put the thermistors there and it will read room temperature, or put a resistor like 100k to 10k in its place so it will "read" some temperature at which it will work.

Thanks so much for your help! Which pins are the thermistors (resistors in this case!) to be plugged into?

Alright! I wired a 100k resistor over each of the thermistor ports and with the correct configuration, the RepRap now reports a sensible temperature! Yay!

However: the motor will still not move and I'm not sure what to do.

Lots of questions to help diagnose your issue..

Do you have 12v wired into the 12v 5amp ramps power socket? this is used to power the steppers. is this power supply on?

Is the Stepper driver plugged in the correct way? Please provide clear photo of the board as it is currently wired. See if we can see anything

Is the stepper wired correctly, if you have followed any color based diagrams its probably wrong. Identify the coils and make sure coil one is on pins 1 and 2 and coil two is on pins 3 and 4 of the stepper plug. More info here

Have you set the correct board type in your firmware (normally 33 for a ramps)

Have you adjusted vref (slightly different depending on your driver) eg [reprap.org] eg [reprap.org]

Are there 3 microstepping jumpers plugged in under your stepper drivers?

Do you have endstops configured or disabled? (If they are enabled, you cant move in the direction that is triggered) check with a m119 command to the board

And finally what type of stepper is it? as some just need to much current or voltage and aren’t suitable to be driven from a pololu type stepper driver.

Edited 6 time(s). Last edit at 07/16/2014 03:23AM by Dust.

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Dust
Lots of questions to help diagnose your issue..

Do you have 12v wired into the 12v 5amp ramps power socket? this is used to power the steppers. is this power supply on?

Yes, it is a 12V power supply that can supply up to 4 amps.

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Dust
Is the Stepper driver plugged in the correct way? Please provide clear photo of the board as it is currently wired. See if we can see anything

I've checked it over with several people. If there were pulses being output then the stepper motor would twitch, correct? Yet there is not so much as "locked resistance", i.e. no direction supplied to the motor but power supplied to the motor.

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Dust
Is the stepper wired correctly, if you have followed any color based diagrams its probably wrong. Identify the coils and make sure coil one is on pins 1 and 2 and coil two is on pins 3 and 4 of the stepper plug. More info here

I am completely sure that the wiring is correct. My Sainsmart RAMPS 1.4 has the pins labeled as 2B, 2A, 1A, 1B, which seems to be the reverse of what one would expect, but either way I have taken this into account.

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Dust
Have you set the correct board type in your firmware (normally 33 for a ramps)

That I have.

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Dust
Have you adjusted vref (slightly different depending on your driver) eg [reprap.org] eg [reprap.org]

I have not tried this yet, at least not so methodically. I tried turning the pot numerous rotations in either directions while telling the motor to move back and forth, yet nothing happened.

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Dust
Are there 3 microstepping jumpers plugged in under your stepper drivers?

I hadn't tried that. However, I plugged in various combinations of one, two, and three steppers and got nothing each time.

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Dust

Do you have endstops configured or disabled? (If they are enabled, you cant move in the direction that is triggered) check with a m119 command to the board

I didn't really attempt to configure them, I figured that since they weren't plugged in the signal to stop the motors would never be given and the motors would run. Perhaps I am incorrect?

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Dust
And finally what type of stepper is it? as some just need to much current or voltage and aren’t suitable to be driven from a pololu type stepper driver.

The driver is an A4988, the motor is a LIN Engineering 417-15-03-14RO. 1.2 A and should work with 12 V.

Thank you for your patience =)

bit late for a full reply, so this is quick...

check those endstops. Normal setup is if the switch is open or disconnected, it is treated as triggered and will stop movement in that direction.

re the vref, it only spins 360 degrees, so spinning it a number of revolutions doesnt help anything.. (most have stops so they only move about 270 degrees)
put it back to mid position for now (there should be a flat edge, make sure thats pointing away from the legs)

Put all 3 jumpers on the microstepping jumpers

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Dust
bit late for a full reply, so this is quick...

check those endstops. Normal setup is if the switch is open or disconnected, it is treated as triggered and will stop movement in that direction.

re the vref, it only spins 360 degrees, so spinning it a number of revolutions doesnt help anything.. (most have stops so they only move about 270 degrees)
put it back to mid position for now (there should be a flat edge, make sure thats pointing away from the legs)

Put all 3 jumpers on the microstepping jumpers

Installing the endstops for the RAMPS board did not fix the problem sadly, and neither did installing the microstepping jumpers. I got a replacement setup figuring in the possibility that the electronics itself might be defective, but no dice, unless this is the second defective Sainsmart kit in a row...

Do I have to do anything special, beyond plugging the RAMPS into the Arduino, feeding the RAMPS power through the 5A power source (as 11A ordinarily goes to the hot end / heated base), plugging the Mega into the laptop via USB, to turn on the RAMPS / enable motion? Perhaps it is somewhere in this that my problem lies. The LCD screen works just fine, incidentally.