A1 Electronics

At this point, to proceed further with the assembly I need to be able to turn the printer on, see it report it's status, and give it commands from a PC to move the various axis and turn on the extruder and bed heaters.

The Assembly Wiki has a pointer to an excellent video by Alastair Seggie on Connecting the LCD Controller. I started there. The Software/Electronics Wiki  points out that the LCD controller cable blocks the airflow from the fan. Here's what I did to move it.
The fan has been removed, the LCD cable is in place and new mounting holes have been drilled for the fan
Fan mounted using small ty-wraps.


So, now we're ready to connect a PC and power on for the first time.
(new info added)
In order for your PC to connect to the RAMPS Ardunio board you are going to need a driver installed. You can find the driver code at http://docs.trinitylabs.com/ download the Taurino Aluminatus-windows-usb-driver.RAR file. Windows doesn't know how to open a .RAR file. You'll need something like 7-Zip software, freeware available from http://www.7-zip.org/  It will unpack into a DRIVER_TAURINO directory with one file, TAURINO-ATmega2560.inf in it. Remember where you put that file.
DO ALL OF THIS BEFORE YOU FIRST PLUG THE USB CABLE INTO YOUR PC!
When you plug in the USB cable, windows will pop up a "New Hardware Found" window and want to look for a driver. It's better to not let it search your PC for the driver. Instead, point it to the directory where the TAURINO-ATmega2560.inf file is located.

You will also need to install the Pronterface software. The Software/Electronics Wiki has pointers where you can download the code. Those of you who are used to windows programs that install themselves you are in for a surprise! The downloaded code will unZip into a directory "printrun-Win-Mar2012-slic3r" (Pronterface includes a copy of slic3r!). For Windows, drag & drop a copy of the directory into your Program Files (x86) directory. Then using Explorer open the "dist" directory, right click on "pronterface.exe", from the drop down list select "send to" and then "desktop (create a shortcut)". Now you have a desktop Icon you can click on to start up Pronterface.
On the desktop, if you right click the icon you can edit the name to be just "Pronterface" instead of "Shortcut to Pronterface.exe"


Pronterface connects to the RAMPS @250000 baud and reports everything OK. At this point, the RAMPS is being powered from the USB cable.

However, when I turn on the power, I get an immediate error message: "Extruder switched off. MINTEMP triggered!"

I used Google to search for this error message. What it's trying to tell me is that the RAMPS board isn't reading the extruder thermistor properly.

Unfortunately, there isn't any documentation on how the A1 is wired up. If you Google RAMPS Documentation you can find a diagram showing what all the connection points on the RAMPS board are for as well as a wiring diagram.

NOTE: my RAMPS board was wired differently in that the two Z stepper motors are driven from Z and E2 rather than both being driven from Z as shown on the wiring diagram noted above.

I pulled the Thermistor connector at the RAMPS board and measured with an Ohmmeter. There was an open circuit.
I measured at the J-head 121K ohms (close to the 126K ohms that I measured for the bed thermistor). Clearly something was not making a connection.
The J-Head Connector has 4 wires
black orange black orange
heater-1 heater-2 Thermistor-1 Thermistor-2

The mating Connector is wired
black black orange orange
RAMPD D10- Thermistor-1 Thermistor-2 RAMPD D10+
So now we know the source of the problem.
The question is how best to fix it.
Eric in TL support was asked if it would be feasible to swap the female connector pins in the mating connector. Or if they could supply a replacement cable. I never saw a response.
After waiting a day or so I went ahead and swapped the pins.
It fixed the problem.

TL - Areas for improvement. You need to test wired assemblies to make sure they are correct. Clearly this A1 was never powered up.  Support needs to respond to customers with system that are not functioning.
At this point I've got a "Functioning" A1. I can move in all three axis and I can turn on both bed heater and extruder heater and see the temperature go up to the requested set point. Temperatures typically overshoot and then come down to the set point. I have not done the PID tuning (yet) that should fix the overshoot problem.

(new info added)
Finally, Check to see if your extruder in moving in the correct direction. The RAMPS firmware has an interlock in that the extruder must be up to temperature before it will try to extrude filament. So the first step will be to set the extruder temp for PLA and see it warm up.
While you are waiting for your extruder to warm up loosen up the bolts that hold the idler bearing against the extruder hub so that you can see the hob move.

Find the Pronterface box that says "Extrude" if should be set to 5mm. You can increase that to 20mm so the hob will move for a longer time.

When the extruder is up to temp, click on "Extrude". If you are too early you'll get an error message, otherwise the Hob should rotate. Hopefully, it's rotating so that it will draw fiber Down from above and push it into the extruder barrel. If not, your extruder is reversed.

To fix a reversed extruder, With the Power OFF!!!, the easiest thing is to remove the 4 pin connector at the RAMPS E0 connector, turn it around and re-install it.

Before I moved on to do the mechanical alignment I thought I would make a change in the endstop wiring while my A1 was torn open. There have been numerous forum comments about electrical noise triggering a false endstop. It's summarized in the Software/Electronics Wiki. I decided to install 4.7k ohm pull up resistors on my endstops and to change the Y and Z endstops to shielded cable (the X endstop was already a shielded cable). Note that +5v for the pull up resistor is already present at the connector. I used shielded cable from an RCA audio cable for my wiring. If you do this you'll find that both cables are the same length. Mine were 39 inches long. Here's how I modified things.

Start by removing the outer sheath and twisting the shield wires together. Remove about 2 in of sheath, cut the shield to about 1/2 in. Twist with a piece of light gauge wire ( I reused some of the existing End  stop wire).
Solder the wires and cut short.
Left: put a short piece if heat shrink over and shrink in place
then cut the wires to equal lengths, remove about 1/4 in of the insulation and tin the bare wire.

Prepare the switches by removing the old wire and solder. If your switches are very tight on the bolts you might want to slightly enlarge the holes. Be careful not to expose the terminal to the bolt.
The center switch terminal is the normally open one and goes to the center conductor. The outer terminal is the common and goes to the shield. Don't forget the heat shrink. Solder the wires.
Left:  Completed switch wiring with  shrunken insulation
You will need 3 1/4 watt 4.7k ohm resistors. cut the leads to about 1/2 inch. Crimp on a mating contact. If you are not using a crimping tool you might want to solder the contact.

Cut the two non-shielded end stop connectors to a few inches of wire. For the shielded endstop by cut only the signal wire.
Connect the ground wire (black, center pin) to the cable shield & solder. As before, insulate with heat shrink tubing

Above: Cut a piece of shrink tubing so it will completely cover the resistor.
Right: shift the tubing so it's over the signal wire of the cable. You are going to solder the two signal wires (cable and connector) to the top end of the resistor,
Left: trim the blue wire to length. Remove the insulation from both
Twist, solder together, then slide the tubing in place and shrink.

Next Step: Alignment

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