RAMPS 1.4 w/ direct short of 5A circuit

Hello,

I've just recently finished a build of a Prusa i3xl from the xssink/DIYTechshop site and tried to get things going today with no luck. What I found was something kinda weird and I'm not sure if its normal, but resistance from + to - on the 5A channel was 0 ohms giving me a direct short, meanwhile the 11A channel showed completely open. Because of this whenever I connected my power supply the voltage tanked to nearly 0V so obviously nothing worked. What makes things more confusing is that before I figured this out, I actually got my power supply to come up once to 12V with no issues although nothing but temperature feedback on the board worked (essentially the short was there, then it wasn't, and then it was). I had no issues connecting up to the Arduino Mega 2560 and when attempting to run the test program all I got was a flashing LED on the RAMPS board with no movement or noise in any axis. Also tried a setpoint for the extruder head and temperature didn't change at all (but it did when I put my hand on it so I know that was working).

Either way, befuddled I've stripped the board down bear, removed all the motor connections, jumpers, steppers, etc, and I still have the direct short. There's nothing I can see visibly on the surface of the board that could be causing the short. I would guess the short is a result of a failed component, but I do not think it's normal (it would be interesting to know what resistance should be across those two terminals). Unfortunately I do not have another power supply or RAMPS to test, so I'm leaning in favor of a bad RAMPS board. Also, this board came assembled in the kit and I did not do any of the assembly. Thoughts? Has anybody seen this before?

Sounds like your D2 diode may be shorted?

Edited 1 time(s). Last edit at 10/27/2013 04:44AM by waitaki.

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Waitaki 3D Printer

That would definitely do it, but isn't F1 MFR500 a fuse? If so it would definitely have to be blown and its showing continuity. I don't have a jumper on the 12V-AUX pins next to D2, so the next thing in line (according to the diagram I"m looking at) is D1, but it checked OK. If nobody has any other suggestions I may remove D2 and see if the short goes away. Does anybody know what it is for? Is it just protection against +/- reversal on incoming power? Or maybe surge suppression?

Also, where can i find an explanation of what all the jumpers are for and how they should be set up? Right now all three jumpers for all 5 steppers are closed, but then nothing else on the board is.

I'm going by this diagram:

[reprap.org]

Actually it could definitely be anything else after D1 showing continuity across D2. It looks like the only thing after that D1 though is "AM-VIN" which is just a pin on the adruino mega connector and if the short is still there without the arduino mega then I think there must be debris bridging something to GND or a bad diode. I think the only way to tell where the short is coming from is to start taking components off the board.

Nevermind, couldn't help myself and I just took of the D2 diode and it is definitely bad. Going to get another one and see what I got.

Alright, a new diode has taken care of the short and now allows me to put power on the RAMPS board without any issues. What has me confused now is whenever I plug in the RAMPS board to the Arduino MEGA 2560 it immediately kills the Arduino board (LED's go dark). It does this even with the power connector removed from the RAMPS board.

Nevermind, I had the endstops hooked up backwards. Anyways, the RAMPS and Ardunio boards are good-to-go. I've got movement in every axis except the extruder, which I am fairly certain is a incorrectly pinned-out cable. I'll swap cables and find out.

Anyways, my hangup now is the endstop logic. RIght now my endstops are are Normally Closed instead of Normally Open and the default Marlin firmware wants the opposite. It seems in the configuration.h there's quite a few options for endstop configuration. I don't think I need to add/remove a pulldown resistor, but instead need just to reverse the logic for what the firmware is looking for. I tried reversing the variables below with no luck.

// The pullups are needed if you directly connect a mechanical endswitch between the signal and ground pins.
const bool X_ENDSTOPS_INVERTING = true; // set to true to invert the logic of the endstops.

// For Inverting Stepper Enable Pins (Active Low) use 0, Non Inverting (Active High) use 1
#define X_ENABLE_ON 0

But neither were what i needed. I guess I'll try commenting out the endstop pull-up resistor.

Nevermind, I got it. I have all the firmware setup correctly and everything works except the extruder, which is definitely an issue with the pin-out. I guess the larger stepper motors use a different pinout than the smaller ones? I tried one of the cables from the other axis and got no movement, but the cable I have which is a different pinout just oscillates hard no matter what the orientation (I removed the gears so theres nothing on the extruder end).

Is there somewhere that shows which pins of the connector on the larger NEMA 17 motors are 1A, 1B, etc.? I think I could probably switch 1B and 2B and I'd have what I needed but I'd rather look it up.

Have you checked the voltage on the extruder pololu board?

Does this help?...
[www.reprap.org]

You're doing very well by the way

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Waitaki 3D Printer

Yep, that's exactly what I needed. I'll have to ring the coils out tonight and do a little trial and error and then I should be up and running. Thanks!

Alright, only took a few minutes and I got the extruder motor running fine. Looks like I need a calibration and am ready for the first print.

Don't stay up too late!

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Waitaki 3D Printer

BTW: The "Fuses" are PTC re-settable fuses. Once the failure is removed, they should work again.

The problem is, they take so long to trigger that any sort of fault (such as Diode D2 conducting because it's had a reverse voltage put across it - ie: if someone had connected the PSU backwards on the inputs) that they can actually cause problems instead of solving them.

If instead of PTC fuses, you had real fuses, the fuse would blow, indicating a problem, rather than tripping your power supply.

Note: I saw a Mega fried by a case of someone connecting the PSU backwards recently, that probably would have been solved if the RAMPS board had a standard fuse rather than a PTC fuse. D2 worked for a short period, then went open circuit (due to too much current as the PTC cut in and out constantly), allowing the board to get fried.

Yep, slow acting fuses they are. I smoked my first Ramps 1.4 board, burned a trace right in half. Bought a new Ramps board, then proceeded to try it out with the stepper drivers reversed... GACK! That fried the Arduino Mega.

I replaced the burned up resistor that was in my Chinese Budaschnozzle hot end with a 40W ceramic, New Ramps, New Arduino, Almost there..... I also have a 4 gang auto fuses to protect the circuits this time just in case.... Two for each 12V input to the board, and One for the Hot end, and one for the heated bed... Each rated lower than the board slow fuses to override.

Hi
Im having trouble getting one motor to spin using arduino and sprinter and pronterface i have the small extruder motor connected and its working ive tried different wiring setups and change the steps in sprinter ****any help would be apprieciated ******here are some pics******* the black motor wire is attched to a yellow motor wire

4 x MA860H Stepper Motor Driver Max 80VAC or 110VDC with 2.4-7.2A
4 x Dual Shaft Nema 34 CNC Stepper Motor 8.5Nm(1204oz.in) 34HS46-5004D
4 x Switching Power Supply 350W 60V 5.9A for CNC Router Kits 115V/230V S-350-60

Stepper Motor 34HS46-5004D

Manufacturer Part Number 34HS46-5004D
Motor Type Bipolar Stepper
Step Angle 1.8°
Holding Torque 8.5Nm(1204oz.in)
Rated Current/phase 5.0A
Phase Resistance 1.0ohms
Recommended Voltage 24-60V
Inductance 11mH±20%(1KHz)
Weight 3.9kg

Motor Dimension:

Wire Diagram:

Stepper Driver MA860H

High performance, cost-effective
Supply voltage up to 80VAC or +110VDC
Output current up to 7.2A
Self-adjustment technology
Pure-sinusoidal current control technology
Pulse input frequency up to 300 KHz
TTL compatible and optically isolated input
Automatic idle-current reduction
16 selectable resolutions in decimal and binary, up to 51,200 steps/rev
Suitable for 2-phase and 4-phase motors
Short-voltage, over-voltage, over-current and short-cicuit protection
Electrical Properties (ambient temperature Tj = 25C pm):
Parameters
MA860H
Min.
Typical
Max.
Unit
Output Current
2.6
-
7.2(5.1RMS)
A
Supply Voltage
18
60
80
VAC
+24
+80
+110
VDC
Logic Signal Current
7
10
16
mA
Pulse Input Frequency
0
-
300
kHz
Isolation Resistance
500
-
-
Mohm

Connector P1 Configurations:
PIN Details
PUL+


PUL- Pulse signal: In single pulse (pulse/direction) mode, this input represents pulse signal; 4-5V when PUL-HIGH, 0-0.5V when PUL-LOW. For reliable response, pulse width should be longer than 1.5μs. Series connect resistors for current-limiting when+12V or +24V used. The same as DIR and ENA signals.
DIR+


DIR- DIR signal: In single-pulse mode, this signal has low/high voltage levels,representing two directions of motor rotation. For reliable motion response, DIR signal should be ahead of PUL signal by 5μs at least. 4-5V when DIR-HIGH,0-0.5V when DIR-LOW. Please note that motion direction is also related tomotor-driver wiring match. Exchanging the connection of two wires for a coil to the driver will reverse motion direction.
ENA+

ENA- Enable signal: This signal is used for enabling/disabling the driver. High level(NPN control signal, PNP and Differential control signals are on the contrary,namely Low level for enabling.) for enabling the driver and low level fordisabling the driver. Usually left UNCONNECTED (ENABLED)

Connector P2 Configurations:
PIN Details
+V Power supply, 18~80 VDC or 24~110VDC, Including voltage fluctuation and EMF voltage.
GND Power Ground
A+, A- Motor Phase A
B+, B- Motor Phase B


Model S-350-60
DC Output 60V 5.9A
Wave and Noise 300mVp-p
Inlet Stability ±0.1%
Load Stability ±0.3%
Efficiency 86%
Adjustable range for DC Voltage 54.5V~67V
AC Input Voltage 93~132V/176~264VAC Slected by Switch
AC Input Current 3.6A/115VAC 1.8A/230VAC
Working Temperature -10~50°C
Safety Standards GB4943, UL60950, EN60950
EMC Standards GB9254, 55022, Class A
Weight 1.1kg