gMax Power Supply Connections - Explanation and tips

#1
I posted this reply on another thread as it related to the thread's current discussion but not really the topic. This may make it easier to find.

Here is an explanation of the colored wires for the power supply and what exactly each wire connection between the power supply and the gMax does. Hopefully, this will assist others in troubleshooting power related issues as well as expanding their gMax using the power supply provided (i.e. adding additional LEDs to the frame and having them come on when you push the LCD power button. Very simple.)

Color Wiring Explanation Main Power Supply Connector

Black - GND
Orange - 3.3-3.7v
Red - 5v
Yellow - 12v

Purple/Green/Silver = Signal wire (these are generally the colors used but vary depending on model. There will only be one of these.) When used in a computer, the power supply's main connector would be plugged into the mother board and the computer's power button would close the circuit between this wire and ground. Effectively, jumpering/completing the sensing circuit for the power supply to come on.

Here is how the gMax is using the power supply:

The gMax draws BOTH 5v and 12v from the power supply. The separate Yellow and Black wired connector powers all of the 12v components (steppers, heaters, LED light, etc.) and the 5v (red/black) portion of the 4 wire molex connector powers all of the electronics (LCD/Arduino/Ramps). The other two wires on the gMax molex connector are green and white. The GREEN and WHITE wires flow through the gMax power button switch. The MAIN power supply needs to have the signal wire shorted to GND in order to come on. This is what the printer power button is doing. It is taking pins 3 & 4 on the power supply and basically jumpering/shorting them like the motherboard example given above. This is what SpudWheelie, pointed out when he said to jumper 3&4 directly. The downside of jumpering directly is that you remove the power button functionality from the printer (but it is useful for troubleshooting) and have to directly plug/unplug the printer to turn it on and off (or have the plug plugged into an external switch).

The LCD will come on without the power supply being powered if the printer is connected to the computer via a USB cable. The USB cable provides 5v VCC to the electronics via the Arduino's USB port. So power flows through the Arduino to the LCD and other electronics (i.e. endstops) None of the 12v hardware will be operational though and the power supply needs be on for the printer to be operational even though the LCD may be on.

My LCD screen came prewired and I only had to plug the loose connector into the main electronics board. When I went to power on my printer for the first time, nothing happened. My four wire molex connector was correct and it was seated as far as it would go.- I traced the problem back to one of the wires connecting to the power button on the LCD screen. It had come loose, so it wasn't closing the circuit on pins 3&4 which is what turns on the power supply. This had come prewired so it took a moment to troubleshoot. As far as I can tell, the LCD power button does not illuminate it just routes the 5v vcc to the electronics.

Once all that is sorted out, you can take advantage of the extra power pins available on the MAIN power supply connecter. Here is one idea that proved both cool and useful to me:

I wanted more light under the print head, so I removed the LED strip with 3 LEDs and replaced it with a double density LED strip containing 6 LEDs in the same space. While doing that I thought it would be nice to add another white LED strip overhead on the 18" horizontal frame (useful) and to also add add two RED LED strips under the 18" rails under the acrylic bed (cool) for really cool under lighting. I have a red/black XT so the red underglow under the acrylic bed is really cool. I even went as far as backlighting the frame in red, but that was a bit too much so I disconnected them. The LED strip on the extruder gets it's power right from the terminal block on the print head so that was an easy change. For the overhead and under bed lighting, I didnt want to use a separate power supply and I wanted the lights to come on when I powered on the printer, just like the extruder. So all of the LED strips were affixed to the frame and all of the black and red wires from the LED strips were capped and termintated with a single red & single black wire coming from the bundle. The red wire coming from all the strips (12v+) was plugged into a YELLOW (12v) port on the main power supply connector and the black wire was plugged into a black wire port (GND) on the main power supply connector. Now, when I turn on the printer via the LCD screen button all lights come on at the same time.

I will try and post pictures of my printer with lights and also show the connections but the forum is not retaining the pix I'm uploading.

Note: This same method can be used to draw 5v and 3v from the supply should you need to add additional electronics and such (i.e. camera). When adding components make sure you do not exceed the max current draw capable of the power supply.

Hope this helps.

Larry
 
#2
Very useful information. Thank you for posting, I am sure it will be very useful to anyone adding mods to the gMax.

The GMax draws BOTH 5v and 12v from the power supply. The separate Yellow and Black wired connector powers all of the 12v components (steppers, heaters, LED light, etc.) and the 5v (red/black) portion of the 4 wire molex connector powers all of the electronics (LCD/Arduino/Ramps).
Almost correct. The gMax draws 5v from the power supply for the power button only. To light it up when it is pressed. There are 2 12v circuits from the power supply which power everything else on the printer. One circuit is a 5 amp circuit and the other is an 11 amp circuit. The atmega 2560 chip (arduino mega) operates at a 5v logic level. This is provided by a 5v voltage regulator (drops 12v to 5v) on the Arduino mega. The Arduino mega can be powered several ways. By a 12v circuit from the power supply, a USB cable, or a DC barrel jack. When ever the Arduino mega is powered on the LCD screen will also light up. But both 12v circuits must powered for the printer to be operational.
 
#3
Kyle,

A formal welcome under your new presence - Gordon mentioned you were on board.

Thanks for pointing that out. The gist of the article is to show people how to tap into the extra ports on the power supply so everything added will be powered on by the power button.

I'm not sure why, but my button does NOT illuminate. All four wires going to my button are seated firmly and the polarity was checked. This is why I thought that the 5vcc was being sent back to the electronics and I didn't think the button illuminated. Mine just doesn't work. Which is fine, I only need it to turn the power on and off (jumper pins 3 & 4)

Thanks,

Larry
 
#4
A formal welcome under your new presence - Gordon mentioned you were on board.
Thank you!

I'm not sure why, but my button does NOT illuminate. All four wires going to my button are seated firmly and the polarity was checked.
Like you said, It does not matter too much. The cost of trouble shooting might outweigh the benefit of a lit LED in a button. Especially with your awesome red "street glow"... http://gcreate.com/forum/viewtopic.php?f=14&t=381&sid=b10edb6046b7108a8744a8e10bf12b3c

For info purposes. I would guess the most likely place for there to be a problem is a loose connection in the connector that plugs into the power supply. Or just a bad LED.
Maybe 5v is being sent to the cathode(-) instead of the anode(+).
 
#5
Kyle,

The LED in the button is just not working. I checked the polarity with a multimeter when I first had the problem. I even went so far as to remove the 4-wire molex connector and physically insert 5v+ and - directly into their respective ports on the main PS plug and the green and white wires into their respective ports. The power button has no problem shorting pins 3&4 and starting the power supply and the power supply comes on. I see 5v+ coming off the wire from the PS into the power button via the multimeter so I know I am drawing power which narrows it down to polarity to the connection to the button. The button fails to illuminate even when switching 5v+ and - polarity to the button. So the LED in the button is bad. But if I can't tell my GMax is powered on, I have bigger problems than a non-illuminating button. :shock:

Thanks for the reply,

Larry