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Messages - HaniC

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General Questions / Re: Weak laser problem
« on: February 10, 2017, 05:41:40 AM »
More description of the problem and clearer explanation or you won't get any help here

Sometimes, I read the various forums I'm active on and feel smart.  Sometimes I feel like the dumbest person there.

So, I'll have you smart engineer types that are making me feel dumb tonight know, I can drink beer through my nose and hum The Star Spangled Banner at the same time.  Take that !

A far more useful skill!

Haha, glad you worked it all out in the end.

My guess is that either they purposely wanted to seperate the reference ground for the power and the signal on the driver board in order to support a particular control board.

Or, the input to the circuit that converts the PWM signal to an analogue current supply to the laser, expects a differential signal to a diff amp. So without ttl-, it's left to float and the input saturated to max current.

This part of the circuit should be imoroved by design, nevertheless

For test connect the +12V pin to +12V and all the three others (GND, TTL+ and TTL-) to the same ground point on the L7 and see if you laser turns off. If it doesn't, the driver is definitely buggered. If it does turn off, go to step 2. (Note: Take a photo showing where you have made the +12V and Gnd connections on the L7, you could have tapped off the wrong place).

Step 2, connect +12V pin to +12V, GND and TTL- to ground, and the TTL+ pin to where you have it connected in your photo. Then go through the process of the structured power up - eg. Connect USB, connect to serial from software then power on L7. If the laser doesn't turn off, then either you connections are no good, or the firmware has not been set up correctly or worse yet you've buggered the arduino.

Um, your TTL - pin should probably be connect to ground! Do not connect it to laser pin. If you've done this, then you could have done some damage to the arduino. 

(Laser) - (L7)
+12V   - +12V
Gnd     - Gnd
TTL +   - Laser pin (As in your picture)
TTL -    - Gnd

It may be possible that the TTL- is not required but it could also be causing your issue if it's left to float (open circuit).

I am "assuming" that the manufacturer actually has tested the circuit with a ttl level drive such as the 5V AVR used on their associated controller. I have been using my home controller board with a 3.3V STM32F303 chip. Next rev (hopefully the last) is about ready and want to have a warm feeling that the TTL port is ok. Guess I should just order one prior to getting the controllers built.

Not saying it doesn't work as intended because it does and it works quite well. The only issue is how THIS PARTICULAR laser driver is configured to handle open circuit input OR uninitialized AVR/Arduino pin. This part of it is just poor design. The only solution is to make a hardware modification OR follow a structured power up procedure as even eleksmaker have defined in point 3 below.

FWIW, I figured out what value resistance to place across the TTL input on my laser controller empirically. I stuck a pot across the input and cranked down the resistance until the laser turned off, took about 3/4 of that value and have been running mine with a 1K6 resistor across the input for a while. Mine had a 5k1 pull-up on the board. Others here have showed concern regarding the extra loading on the Nano but it works for me. YMMV.

This is becoming a very popular question on this forum. There are several options available for a fix depending on the owners expertise. Not everyone understands electronics, wants to modify the foil traces or unsolder components on their brand new laser module. It would be nice to establish a "work flow" so when it comes up again, the forum member has an organized method to follow. I realize there are a lot of different controllers out there to deal with so a general work flow would seem appropriate.

The type of driver the OP has is different to what you have. I also assumed that one should simply be able to hold the input low with a low enough impedance but I in testing I got down to a <100 ohm pull-down and it still DID NOT TURN OFF. So I assume, it's not a simple schmitt trigger input that just needs to be held below the low level of the hysteresis band. It needs to be more of an open-drain type output and I think the only safe way to fix at the main control PCB side is to make a PCB change that is not insignificant for electronics noobs. A simple pull down WILL NOT WORK - You will need to actively hold the pin low.

It may also be fixable at the laser driver board on the laser but I haven't bothered to reverse engineer this as all the ICs have had their MPNs scrapped off.

General Discussion / Re: Problem with low current at 12V tap on L7 board
« on: February 06, 2017, 07:46:40 AM »
Errr, how and where exactly did you measure that current?

These small fans consume a he** of a lot less current than either your laser or your steppers so if your fan is not working correctly while they're off then there is probably something wrong with the fan, where you connected it or how you connected it.

I highly doubt the 12v supply is not sufficient in this scenario if otherwise the machine runs fine.

When connected to that fan port, does it only come on when the laser is on? If so it's probably driven from the same MOSFET that drives the laser so it could very well be PWMed with your laser signal which would reduce the you hear the fan speed change at all?

One thing I fear though is what happens when the engraving is done? Hopefully the laser stays off!

It will. Just think of it this way, you only need to power the Arduino to get it to initialize. Once it's been initialised, it won't turn the pin on until you/gcode tells it to.

The only time it will then turn on by itself is if you disconnect and reconnect the serial port from the software. Even then it'll only do it for a second or so.

The only persistent on state is when you supply the +12v without powering the Arduino by not connecting the USB to the PC.

DO NOT DO THAT, you'll prob kill the laser driver and/or the laser

Note: in reference to you using 12v to control laser as before.

Ahh, just checked you banggood link. It's the same driver as mine (mana SE) so don't stress out. What you're seeing is COMPLETELY NORMAL for this driver. It's normal but a bad design.

The mana SE laser does the same thing. When the PWM (D11) pin is high or high-impedance (as is the case at first startup) the laser is ON. The laser turns off only when you connect the usb to your PC and connect to the software - eg. after the arduino firmware has initialized the pin to output low.

I have experimented with a pull-down resistor on this pin to hold the pin low during this initial period but it doesn't work so I'm assuming the driver expects a much lower impedance path to ground, to turn of the laser, as is the case through the arduino's complimentary output fets.

If you remove the Arduino completely, connect the D11 pin to ground and the laser turns off, then you have the same type of driver and the same issue but your LASER and DRIVER are probably FINE. My workaround is to just connect the arduino to the computer, launch whatever software, and wait to get the "GRBL 1.1e" start message AND THEN power up the +12V side.

I haven't had a chance to test the fix but I imagine we will need to buffer the D11 output with a TTL buffer OR complimentary pair that has it's input pulled down to ensure the driver input stays low until it is ACTIVELY driven high by the arduino.

So my advice is test, with arduino removed (as described above). Then test with the correct power up procedure (also as described) and then just use my workaround until I or someone else get a chance to test a good simple solution.

T2 Engraving / Re: Setting Work area size
« on: February 05, 2017, 11:39:28 PM »
Im not sure if Zax put commands in to do this within T2 but if you can manually send gcode, just send one command per line:
Eg. Just type:

For 100mm and so on.

T2 Engraving / Re: Setting Work area size
« on: February 05, 2017, 08:00:47 PM »
$130 and $131 sets max area.

So for example,  issue a $130=200 for max 200mm in Xaxis and $131=100 for 100m Yaxis max

General Discussion / Re: First large greyscale attemp
« on: February 05, 2017, 07:56:27 PM »
I think you mean gcode

GRBL is the firmware

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