Posts Tagged ‘Electronics’

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The wiring harness

December 10, 2011

Today I took on the relatively arduous task of mapping out the wiring harness as it will need to be totally replaced. Fairly large portions of it are severely burnt/melted, more than I had initially noticed/assessed. For the most part it it is fairly straight-forward point-to-point connections. I started with the door sensor loop, as it is the most damaged.

Door Sensors & Bypass Circuit:

CTL[13] --- + --- <RSL> --- <LSL> --- + --- <RSD> --- <LSD> --- CTL[9]
             \                       /
              \ --- --<     >-- --- /
                 Lid Sensor Bypass
RSL/LSL: Right & Left Side Lid sensors
RSD/LSD: Right & Left Side Door sensors

As you can see the magnetic door sensors are simply connected in a loop. There was a mystery connector on the top of the chassis, as it turns out this is used to form a bridge across the lid-door sensors, effectively bypassing them to allow operation with the door open. Unfortunately I had to destroy this connector to remove it, so I will need to find a suitable replacement. [I didn’t have the bridging plug anyway]

Next up is the connections to the front panel. I had initially assumed the mystery RC on the control board was for debouncing an input from the wiring harness, but as it turns out it is a straight connection from the main controller to the front panel. So the purpose of the RC remains a mystery for the time being. The connection is a standard IDC ribbon cable [26 pins].

Another unknown [but assumed to be for the rotary attachment] was a completely melted DB9 connector. Once I unbundeled the harness, I was able to confirm that it indeed was for the rotary attachment, as one set of wires went to the stepper driver, and the other to the main controller.  I was able to determine a pin-mapping, but don’t know the function of each line yet. Although the insulation was burnt off, and the connector was melted beyond use, the bare copper of the wire remained, and all the wires appear to have remained in their relative positions.

Rotary Attachment Connector:

1 - Stepper   6 - Stepper
2 - Stepper   7 - Stepper
3 - N/C       8 - N/C
4 - Homing    9 - Homing
5 - Homing

Next I Mapped out the Stepper driver connector, which is a 20pin ATX power connector style connector. The connections are as follows.

 1 - Rotary[6]           11 - Rotary[7]
 2 - Rotary[2]           12 - X[5]
 3 - Rotary[1]           13 - X[6]
 4 - Shield [Rotary]     14 - X[7]
 5 - Shield [X]          15 - X[8]
 6 - Shield [Y]          16 - Y[3]
 7 - Shield [Z]          17 - Y[4]
 8 - Z[1]                18 - Y[2]
 9 - Z[6]                19 - Y[1]
10 - Z[8]                20 - Z[3]

I will need to analyze the stepper driver board to try and determine the wire parings for the motors. Though I may also be able to derive it from the stepper datasheets I can find. Though given the pinout, I am imagining its:

Axis   PhaseA  PhaseB
Rotary  1&2     6&7
X       5&6     7&8
Y       1&2     3&4
Z       1&6     3&8

I’ve confirmed the Z pairing via the datasheet. The motor side has jumpers between 2&6, and 5&7 placing the coils in series for bipolar operation.

The remaining wires all run to the same 34 pin connector [J4] on the main controller board. This connector contains the LASER control, safety loops, and homing & limit circuits.

 1 - CO2 Modulation     2 - Opto Return (Modulation & Diode)
 3 - LASER Diode        4 - N/C
 5 - AIR[5]             6 - AIR[6]
 7 - AIR[2]             8 - BEEP[1]
 9 - DoorLoop          10 - BEEP[2]
11 - INT[6]            12 - LASER Interlock Out
13 - DoorLoop          14 - INT[5]
15 - N/C               16 - N/C
17 - AIR[8]            18 - VCC (XY[3])
19 - GND (XY[4])       20 - LIM[2]
21 - GND (ZLIM[4])     22 - N/C
23 - XHOME (XY[1])     24 - N/C
25 - YHOME(XY[2])      26 - GND (ZLIM[2])
27 - LIM[3]            28 - LIM[1]
29 - Z-LIMIT (ZLIM[1]) 30 - VCC (ZLIM[3])
31 - Rotary[4]         32 - Rotary[9]
33 - Rotary[5]         34 - N/C

I forgot to map out the Z axis limits board (ZLIM) so I’ll need to do that to determine their final functions. [I’ll come back and edit this post once I get a chance to do so]

There’s a trio of unknown connectors I’ve labelled as AIR/INT/LIM; I’m assuming these are for the Air-Assist option. The connectors were present on my harness, but not attached to anything else, with the exception of the INT connector which had a small loopback plugged into it for two of the wires [5&6]. INT and LIM are bundled together, and were located in the back right corner of the unit inside the engraving chamber. AIR and a 48V power connector were located on the bottom of the unit below the laser & electronics [outside the engraving chamber].

The INT/AIR connectors also have a set of wires that runs between them as follows:

INT / AIR
 1     7
 2     1
 3     4
 4     3

Based on the pattern within the main connector, I’m guessing that INT 5&6 form some sort of safety/interlock loop like the door sensors do. [hence the reason they are looped together]. The LIM connections appear to be another set of limit/homing sensors. So perhaps this is not for the air-assist option as previously thought, as I cannot think of why we would need en extra safety-loop and limit detector for air-assist. Though if it’s not for air-assist, I have no idea what it could be for.

The final connector, is the one on the back of the LASER itself. The pinout for it was pulled from a ULS OEM LASER manual.
LASER Pinout:

1 - +48V    4 - N/C           7 - GND       10 - N/C
2 -  N/C    5 - Interlock In  8 - +12VOut   11 - LASER Diode
3 -  N/C    6 - Modulation    9 - RET       12 - N/C

Note that the pinout does define additional signals, but I’ve only included the ones connected in my harness here.

Actually there a re a few more connectors, but they are for power, which is straight forward. And the two break-outs for the back panel connectors to the mainboard, which are of no consequence here.

[Update]Added the Z-limit signal assignments. The board is arranged differently than I had imagined. I had assumed the two LED’s would have been in parallel, and each limit would have had a discreet output, given the 4 pin connector.  But the board is actually arranged such that the two LED’s are in series, as are the two photo transistors. In this arrangement if beam is broken at either detector the sense loop goes open circuit. The only downside to this arrangement is that you have no idea which side was broken, but one can extrapolate that from the direction of motion. [assuming everything is set up correctly][/update]

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X motor PCB’s

December 6, 2011

Almost forgot, there is a pair of small PCB’s that need to be mapped… The PCB that sits over the X stepper motor, and the one that connects the flex cable to the main wiring harness. For all intents and purposes these two PCB’s can be thought of as a single PCB, and that’s how I’m going to handle them [it looks like ULS looks at them like this as well, based on their component designators]. The main wiring harness plugs into the lower PCB which is bolted to the chassis. This PCB simply passes the signals onto a flex cable, that runs the signals up to the upper PCB, which then breaks them out for the X stepper motor, and the X & Y homing sensors. With the exception of a handful of capacitors, and a couple of resistors, there really isn’t anything to the PCB’s.

Read the rest of this entry ?

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The front panel (part 2)

December 2, 2011

Today I took on the front-panel control/display board. The board is pretty much charred as you can see. It has quite a few traces on it, but is fairly simple in function, thus making it relatively easy to decode.

Before even doing any cleaning I tried  to make some pretty good guesses as to the architecture, the next paragraph is my assessment from before I started.

There are 2 IC’s on it, which are likely some sort of tri-stating buffer, allowing the switch signals to be multiplexed onto a data bus. The data bus also feeds to the LCD.  Then there are the 2 LED’s, these are fairly large and probably consume a bit of current, which would explain the two transistors beneath them, likely acting as low side switches. There’s a 3rd transistor on the board, which I’m not sure of the function yet, but it should become more obvious as I trace it out.

Now lets get into it and see how well my guess did.
Read the rest of this entry ?

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The front panel (part 1)

December 1, 2011

Today I took a bit of time after work to map out the membrane keypad of the control panel. Unfortunately it was badly burnt up, so unusable, and I didn’t take the best of care pulling it off.

However, fortunately enough, it mostly came off in large pieces, so I was able to put the pieces together enough to trace out the signal mapping. to make life a little easier, I took a picture from the backside where the traces can be seen, and then traced out the lines in CorelDraw. Virtually any membrane keypad can be reverse engineered this way, as they are almost always printed on transparent material. Read the rest of this entry ?

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And then a step to the right

November 30, 2011

The search for replacement stepper motors is on. The first step was identifying what is there already.

Two of the 3 steppers (X & Z) are easily identifiable, as I can read the labels on them. The 3rd stepper (Y) unfortunately has had the label completely darkened from the fire to the point where all I can tell is that is is a 0.9 degree/step stepper from the one side that is still readable.  Luckily with a peek at the laser at the Hacklab, and at a picture posted by a user (lasersafe@buildlog.net) of another ULS laser rebuild, I was able to identify the make, and possibly model for the unknown stepper. It is definitely the same manufacturer / series based on what is still discernible on the label of the motor. However it is quite possibly a different model than the one that is in both the Hackalab’s laser, and lasersafe’s UL25E. (the part number, while unreadable appears to be different) Read the rest of this entry ?

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On the mark

November 19, 2011

I decided to fire up the laser again, and get some pictures this time. So while I was at it, I decided to check the beam alignment between the visible and burning laser beams. I also got some pictures of the test set-up.

The key switch is for the safety loop, the burning laser will not fire unless the key is in, and turned. The trigger-switch is bi-directional, with one direction firing the red pointing laser, and the other firing the burning laser. There is no reason why the two cannot fire at the same time, it’s just what I had sitting on my shelf. The laser itself requires 12V for the safety loop [it can provide it, but my wiring harness does not have that pin connected] Also required is 5V for the firing control, this must be externally provided. Finally the laser needs 48V to power the laser itself. The 48V is taken from the original power supply, while I am providing the 12 & 5V from a lab supply.

To Check the laser up as above, with a piece of white card-stock taped to a concrete block wall, about 2ft away from the laser. I then fired the visible laser and marked the location of the spot with a pen on the paper.

One might notice that there are 4 red spots. One main bright spot, and 3 more smaller fainter ones. I’m not exactly sure why they’re there, but I’m assuming it is a result of the beam combining optics. They use what is known as a 45° hot-mirror, which reflects the IR light of the laser, but passes the visible light through. This is what allows the two laser beams to be perfectly aligned. So in the case of the ULS laser the setup is as follows.

I’m guessing the extra spots are the result of some internal reflections of the red laser within the mirror glass. Either way, they are not an issue. After marking the main spot, I proceeded to fire the CO2 laser, and then re checked with the visible laser. I tried my best to capture the moment of the laser firing, but it just shows up as a large bright white spot. This flash of light is from the material burning, not from the laser itself.

As you’ll see from the image below, the alignment is pretty darn good. So from my perspective, the laser is in perfect operating condition. I may just have to swap out it’s air-cooling fan, as it made some noise the first time I powered it on, though it did not make it again this time around.

So there it is, a fully functioning CO2 laser 🙂 This was probably the last time I fire the laser until I have it back in the enclosure. I don’t like to fire it in the open like this for safety reasons. So for now I’ve covered up the optical aperture on the laser to prevent it from getting dirty, and placed it on the shelf. Hopefully I’ll get a reply from the ULS rep soon, so I can start moving forward on the actual re-assembly of this thing.

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X marks the spot

November 19, 2011

Finally the X axis movement.

The X axis movement is constructed of a light-weight thin-walled extruded aluminum [or some other lightweight alloy] channel. It needs to be lightweight in order to minimize the mass, allowing for higher movement speeds without overshoot. On it, rides the lens and focusing carriage. There is a belt that runs along the front, and then returns inside the channel to the stepper motor on the truck/carriage of the right-hand Y axis rail that moves the cutting head. The laser beam comes in from the left, via a mirror that sits on the truck of the left hand Y axis rail.

Unfortunately, because it is so light weight, this axis suffered the most damage in the fire. It is completely unusable as it is. The rail itself is warped into an arc, the belt is all but gone, and the head is encased in the molten glass from the viewing window. [I found out the top window was indeed glass, and not acrylic as I had surmised in an earlier post] I am hoping to get a replacement rail from ULS, but this may not be possible. If I can’t I will likely use some stock aluminum extrusions one can find at the local hardware store. This solution will be slightly heavier, but should still work fine.

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