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SHUMATECH DRO-550 Construction Manual

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DRO-550 Construction Guide (rev. 2)
S
T
HUMA
ECH
DRO-550 Construction Guide
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Summary of Contents for SHUMATECH DRO-550

  • Page 1 DRO-550 Construction Guide (rev. 2) HUMA DRO-550 Construction Guide...

  • Page 2: Table Of Contents

    DRO-550 Construction Guide (rev. 2) Revision History Revision Description Original version Added board rework step 9 Table of Contents Assemble the PCB .......................... 2 Step 1. Parts Inventory........................ 2 Step 2. Visual Inspection ......................4 Step 3. Electrical Test ......................... 5 Step 4.
  • Page 3 DRO-550 Construction Guide (rev. 2) descriptions of the parts in clockwise order on the picture at left starting from the the DRO-550 printed circuit board (PCB). You can click on this or any other picture to get a larger view of it.

  • Page 4: Step 2. Visual Inspection

    DRO-550 Construction Guide (rev. 2) Step 2. Visual Inspection The DRO-550 circuit board is professionally manufactured on a modern, surface mount assembly line. To keep the power buy price as low as possible, the boards are not electrically tested after they are assembled so there is a possibility that the board has an undetected flaw.

  • Page 5: Step 3. Electrical Test

    DRO-550 Construction Guide (rev. 2) There are five identical scale interfaces that are organized in rows down the middle of the board. Each interface has a 4-pin header, two 8-pin ICs, a 2x2 header, and several passive components. Check each scale interface for the three orientations noted in the picture at left.
  • Page 6 1.8V Probe Point 1.5V Probe Point The DRO-550 circuit board contains five power planes: ground, 5V, 3.3V, 1.8V and 1.5V. The board is constructed out of four layers with the power planes existing on the two internal layers. Since there is no way to directly inspect these layers, we will electrically check them for shorts using 5 test points.

  • Page 7: Step 4. Smoke Test

    DRO-550 Construction Guide (rev. 2) combination using the multimeter. For each combination, verify that the resistance is greater than 1K ohm. Reference the pictures to the left that show convenient test points for each of the five planes. The ground test point is the square pad ("-" label) on the J13 header ("9-20V IN" label). The 5V test point is the round pad ("+"...
  • Page 8 You can use solder wick to remove any excess solder. Retrieve the power supply that you are going to use for the DRO-550. It should be between 9 to 20 VDC and be rated for at least 1A. Look at the...

  • Page 9: Step 5. Processor Test

    Type B USB cable into your PC and the other end the USB connector on the left side of the DRO-550 board. Your PC should recognize the DRO-550 and you will get the standard Windows "Found New Hardware Wizard" dialog box.

  • Page 10: Step 7. Solder Led Displays

    DRO-550 Construction Guide (rev. 2) Step 7. Solder LED Displays Install the nine 7-segment LED displays on the same side of the board as the keypad switches. One technique you can use is to lay the 7-segment display face down with the pins pointed up and then lay the board down on top of it by threading the pins through the appropriate holes in the board.
  • Page 11 The program switch is a 6mm, surface mount tach switch. It is used as a last resort to place the DRO-550 intro program mode. Most of the time, you will use the OpenDRO menu interface to enter program mode and the program switch is not used. Since the switch is surface mount, a slightly different technique is required from the other through hole parts.

  • Page 12: Step 9. Board Rework

    DRO-550 Construction Guide (rev. 2) Step 9. Board Rework During testing, one minor problem was discovered with the production boards. The RS-232 transceiver is not reliably picking up 3.3V from the power plane underneath it. The power via is placed on the very edge of the plane and might not always touch it when tolerances are considered.

  • Page 13: Fabricate The Enclosure

    DRO-550 Construction Guide (rev. 2) • Action: Make sure you followed the software programming instructions exactly including setting the flash boot option. Verify that the power adapter is supplying power by checking its DC voltage with a multimeter. If it measures between 9-20V then it is OK.
  • Page 14 DRO-550 Construction Guide (rev. 2) The enclosure is machined using standard milling and drilling operations. Note that when cutting plastic, you should use a fairly high RPM and use a slow feed while drilling or use a wood block or something behind the front panel. The enclosure is made of ABS plastic so use as fast an RPM as possible without melting the plastic.

  • Page 15: Step 2. Machine The Rear Panel

    DRO-550 Construction Guide (rev. 2) Step 2. Machine the Rear Panel The layout of the rear panel is not at all critical and you can machine it however you like. The drawing below shows one possible layout for the rear panel. This layout is based on the DRO- 350 rear panel so if you already have a DRO-350 case with the original layout, then you can just add the extra connector holes that you need.

  • Page 16: Step 3. Drill The Usb Hole

    Step 3. Drill the USB Hole The USB interface is used to both program the DRO-550 and to interface the DRO with a PC to control its functions. The hole for the USB exits the case on the keypad side of the front panel.

  • Page 17: Step 4. Install The Standoffs

    DRO-550 Construction Guide (rev. 2) Step 4. Install the Standoffs The standoffs are mounted to the back panel of the enclosure and attach to the component side of the PCB with the seven segment displays and tact switches facing out. The six plastic posts in the back panel must be tapped 6-32 to hold the standoffs.

  • Page 18: Step 5. Install The Connectors

    The scale connectors are 4 pin mini-DIN type that mount to the back panel with 4-40 x 1/2" black machine screws. You can install up to five scale connectors with the DRO-550. The connectors listed in the bill of materials have a hole on either side that must be tapped 4-40 before mounting with the screws.
  • Page 19 DRO-550 Construction Guide (rev. 2) The DC power connector is a standard 2.1mm type. The connector listed in the bill of materials is a snap-in type that is simply pushed into the hole drilled into the back panel. Depending on the tolerances of the hole, you may need to put a few drops of hot glue or epoxy to assure that the connector does not pull out of the hole when the power cord is removed.

  • Page 20: Step 6. Attach Overlay

    DRO-550 Construction Guide (rev. 2) Step 6. Attach Overlay The overlays are silk-screened onto the back of transparent 10mil Lexan film. They are screened with three colors: black, white, and a near-cyan color. The windows for the seven segment LED displays and the indicator LEDs above them are water clear.
  • Page 21 The tip is 5V to ensure that the auxiliary device is not energized until the plug is fully inserted. The RS-232 interface is used for both programming the DRO-550 and for interfacing it to a PC. The cable is wired as indicated in the table. The connector is a 9 pin female d-sub connector.
  • Page 22 It can be difficult to get a good connection without a lot of fidgeting with the connector. Also, the connector sometimes has a tendency to short across the pads which will either prevent the DRO-550 from reading the scale or even cause the DRO-550 to shut down power to the scales if the positive supply is shorted.
  • Page 23 DRO-550 Construction Guide (rev. 2) PCB. Even if the plugs were available, I would still recommend you do the following to get a solid, reliable connection. What I recommend is to solder the four wires from the cable directly onto the pads on the scale.

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