Ramps 1.4 problem

Hello everyone,

I have almost finished my Kossel mini assembly. However, when i try to power up my electronics board, strange things happen.

When i plug arduino mega alone, it connects perfectly and i can upload the code to the board. Whenever i plug my Ramps board onto Arduino and connect them to my laptop, it connects at first, then disconnects after like 5 seconds. I hear the disconnect sound twice. What is happening here?
Thanks

It sounds like something (misplaced end stop plug, reversed servo plug, etc.) is shorting the 5 volt bus, causing the Arduino to shut down, losing connection to the laptop.

Do you have anything plugged into the RAMPS board when this happens?

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-David

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Thanks for the reply.

I have everything but endstops plugged in.

The only external things that are running on the 5 volt (VCC) bus are the stepper drivers (A4988, etc), the end stops (if they are 3-pin), the AUX ports and the servos (if the 5V/VCC beside the reset switch is jumpered)

Though it is a pain, I would suggest disconnecting everything from the RAMPS, including removing the stepper drivers and seeing if the problem persists. If so, the problem is not a peripheral, but the RAMPS board itself. The good news is that the board is relatively simple and would be easy to inspect for stray solder or touching terminal pins, etc.

If the Arduino behaves with the empty board then one of the peripherals is causing the problem. I would power it down and try inserting one stepper driver (do not plug in the motor) at a time and try again. This will verify each of the stepper drivers are okay. Then, I would proceed the same way with each stepper motor. This procedure will locate the problem, if it is hardware- or wiring-based.

Please let me know how it goes...

---

-David

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I have managed to get over issues, everything works now, but steppers vibrate and roar like crazy. What Vref should i set for my 1.7A stepper motors?

You'll need to have the steppers installed as they will operate during printing. You'll also need to identify your stepper drivers:


A4988 (square chip)


DRV8825 (long chip)

Please take a look at the tuning procedure here...

---

-David

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Allright, I have plugged my A4988 drivers and motors into my 3Drag board, they worked. After i connect them to my Ramps, they dont work smooth, they vibrate, rotate and roar randomly. I set my Vref to 0.55V. I have also all three microstepping plugs installed, whereas there are no microstepping plugs on my 3Drag board, could these be the issue?

Oh. I didn't know you were changing boards...

The configuration.h file needs to be changed to also let Marlin know that you're changing boards. You'll need to change #define MOTHERBOARD 62 (or whatever number your old board used) to #define MOTHERBOARD 33 (or 34, 35, 36 depending on the printer configuration)

Give that a try.

---

-David

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Quote
Capinho
I set my Vref to 0.55V.

.55V for 1.7amp steppers may not be the best value. With authentic A4988 (or equivalent) Pololus, the sense resistor is .05 ohms giving the formula I_TripMax= Vref/(8*Rs) = .55V / (8*.05 ohms) = 1.375 amps. If you have Stepsticks, they have a sense resistor of .2 ohms so I_TripMax= Vref/(8*Rs) = .55V / (8*.2 ohms) = ~.34 amps. DRV8825 drivers the formula is simpler with the I_TripMax = Vref * 2 Ohms = .55V * 2 ohms = 1.1 amps.

Regardless of which stepper you are using, you are well under the limits of your steppers. If you go to low, the steppers may not operate correctly, squeal, make erratic movements, etc.

If you motors are vibrating and roaring it might be a loose connection to one of the steppers motors.

Do NOT connect or disconnect a motor while the board is energized. This kills the stepper drivers and or board.

Do investigate the connections though. Sometimes the pins can be pushed out of the connector and cause a lot of grief.

Many thanks everyone, set my stepper voltage to 0.68, works perfectly. thanks again, guys.