Megatronics V2.0 Problems - Let's Resolve them

Hello every one , at first be aware about to order Megatronics V2.0 from sainsmart.com no document , no support at all from sainsmart , any document they will send to poor buyer came out from this forum and just they put it on 2 page word files !!!! , so be happy to find this topics and go for another board ,

im still working on bunch of problems of this board and saw many ppl bought it , some of them leave it and went for other board or use it at how it is !!


Second For how bought this board already lets make resolve all of the problem of this board at one topic , each problem resolved i will add it to first post so any body able to see and find solution for it , any problem with your board you have please write
Problems :
1- LCD not working with out USB cable , it mean you always need PC or laptop next to your 3dprinter !!!
2- SD card on LCD board not working
3- electronic problem with this board or perhaps it should be from chines company assemble (sainsmart.com) at the moment im not sure

FIrst question about problem 1 (Please Check Pic1)
When USB connected i have on pin 2 4.87V and pin 3 3.3V , When usb remove and board only connect to 12V power supply pin 2 is 3.3V (Why?) and pin 3 3.3V
LCD working only when usb connect and pin 2 has 4.8V , but with out usb pin 2 receive 3.3V and LCD not working only backlight of LCD turn on when push keypad
Im not electronic man but im sure the problem becomes from pin 2 how can i deliver 4.8V to pin 2 when usb not connected



Also please have look on Pic2
Again with USB Connect it shows 5V and with out USB and only with 12V power supply it shows 3.3V
PLEASE HELP ME HOW TO DELIVER 5V TO PINS AND RESOLVE THIS PROBLEM , im sure if i can deliver 5V to the pins even with out USB ,LCD will work fine and can to use printer with out laptop or desktop

No One?

... either there is missing a voltage regulator to get the 5V out from the 12V, or you haven't found (a possibly existing?) option jumper to select the 5V from either USB or from a (possibly existing?) 5V regulator

You can add on your own a 7805 between 12V and GND to get 5V, but then include a switch or jumper to disable it, when the USB-5V are connected too ...

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Viktor
--------
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there is one jumper for 5V only to get from USB nothing else , it is placed next to USB port (blue jumper) , when remove blue jumper no 5V comes to board , i can not see any 5V regulator at the board .

Can you tell me how can i add 5V to my board and what is 7805?

Quote
VDX
... either there is missing a voltage regulator to get the 5V out from the 12V, or you haven't found (a possibly existing?) option jumper to select the 5V from either USB or from a (possibly existing?) 5V regulator

You can add on your own a 7805 between 12V and GND to get 5V, but then include a switch or jumper to disable it, when the USB-5V are connected too ...

Samotras

as you indicate in the private msg just change the transistor ic2 has to be 5v, and solve your problem.

If you have any questions or if you need help, send me a private msg

Reference post [forums.reprap.org]

Hello guys, I have a huge problem I haven't been able to solve for a while now. If you have any knowledge or even a clue to this issue I would appreciate your help!

I have a Megatronics V2.0 running Marlin and I'm trying to control an output pin to switch on and off a relay. I've been able to set up a digitalWrite (and analogWrite) outputting to the following PINs: 6,7,48,44,45,47,49 and it has worked successfully when I send the commands through the manual controls in Repetier Host but when I upload Gcode that has movements it doesn't work properly. It ends up turning on or off when it's not suppose to.

Things I have tried: send Gcode through SD card and the same thing happens. I've also changed the case to M 806 & 807, M 95 &96, M 106 &107, and a few others and the same thing happens. Multiple Marlin versions and Repetier firmware.

This has led me to realize that it has to do with the way it buffers the Gcode and if it gives priority to some more than others. How does this happen? Can someone explain how the buffer allows movements to be sent properly but other codes it just boots it out of proper timing?? Also it messes up consistently on the same Gcode, it's not a random mess up. Say we have M106 then some Gcode then M107 then some more Gcode then M106 then some Gcode then M107 and what it will do is it will turn on and off like 3 times very rapidly at the begging when I hit print and then it will be off when it should be on and on when it should be off. Then it eventually doesn't turn back on.

Anyone who could explain why this happens, or show me what I'm doing wrong, or point me to where I can read more about the buffers would be great!

CODE:

#if defined(FAN_PIN) && FAN_PIN > -1
case 106: //M106 Fan On
if (code_seen('S')){
fanSpeed=constrain(code_value(),0,255);
}
else {
fanSpeed=255;
}
break;
case 107: //M107 Fan Off
fanSpeed = 0;
break;
#endif //FAN1_PIIN
#if FAN2_PIN > -1
case 806: //M806 Fan2 On
if (code_seen('S')){
analogWrite(6, constrain(code_value(),0,255));} //D6 is fan2_pin as in pins.h
else {
analogWrite(6, 255);}
break;
case 807: //M807 Fan2 Off
analogWrite(6, 0);
break;