Fab@Home:Model 1 Electronics
From Fab @ Home
Welcome to the Fab@Home Model 1 Electronics Overview
The Model 1 Electronics consist of:
- Elpac MW4024-760-NC-WH 24VDC, 1.67A (40W) Power Supply
- AC Power Cord (IEC 3 prong to USA 3 prong plug) for Power Supply
- Olimex LPC-H2148 Microcontroller Board
- Xylotex XS-3525/8S-4 4-Axis Stepper Motor Amplifier Board
- Winford Engineering DB-25 Breakout Board
- Omron D3M-01K3 SPST-NC (Single-pole Single-throw Normally Closed) Limit Switches
- Limit Switch Cables
- Ribbon Cables to connect the LPC-H2148 to the other devices
- USB Cable to connect LPC-H2148 to the user's personal computer
Constructing the Model 1 Electronics
The following steps are required to assemble the electronics for the Model 1:
- Prepare the motor cables
- Prepare the limit switch cables
- Prepare the ribbon cables
- Prepare the amplifier enable cable
- Prepare the power supply cable
- Route the cables
- Modify the Xylotex Board for the Limit Switches
- Attach the Enable Cable to the Winford Board
- Mount the boards onto the chassis
- Connect the cables to the boards according to the schematic and the electronics pinouts
Modify Xylotex Board for Limit Switches
Note: Do not ever measure across the motor outputs of the Xylotex board with a scope! You will kill your board. Also, if you recently purchased a kit from Koba Industries Inc. you do not need the Winford board.
The Xylotex XS-3525/8S-4 4-Axis Stepper Motor Amplifier Board is nicely designed with a set of screw terminals to allow simple connection of devices to any auxiliary input/output signals coming onto the board via the IDC26 connector. We will use these terminals to connect our limit switches, and the limit switch signals will then travel to the LPC-H2148 via the IDC26 to DB25 cable, through the Winford board, and then over the IDC26 cables to the microcontroller. In order for the limit switches to provide a signal, they need to change the voltage on the Xylotex aux IO pins when the switch is activated - this is generally achieved by placing the switch in a series circuit with a resistor, and monitoring the voltage between the resistor and the switch. There are two configurations for this circuit - Vcc->switch->resistor->ground ("pulldown"), and Vcc->resistor->switch->ground ("pullup"). Pullup is generally preferred for safety, as the resistor between Vcc and the other components limits current in the case of a short. In ether case, when the switch state changes (opened or closed), the voltage between the switch and resistor changes from Vcc to GND or vice-versa. The Xylotex board does not have these pullup or pulldown resistors onboard, however it does have a nice spot for a 10pin SIP (single inline package) resistor network - 10 tinned holes just behind the black aux IO screw terminal block. The resistance of a single resistor should be about 10 kOhm. Because of the on-board connections to these holes, we have opted to use the "pullup" circuit configuration, and you will need to run a wire from a Vcc (5VDC) screw terminal to the screw terminal at which pin 1 of the SIP is connected (see the schematic below). Here you will see how to solder the 10pin SIP network onto the board.
 Step 1: Here you see the Xylotex board and the 10 pin SIP resistor network, and the destination for the SIP highlighted |
 Step 2: The SIP has been inserted into the tinned holes prior to soldering. Note the orientation of the "Pin 1" marking. |
 Step 3: Bend the first and last lead of the SIP slightly to keep it from falling out during soldering. |
 Step 4: Apply a small amount of flux to each of the leads of the SIP |
 Step 5: Heating the lead and the tinned hole simultaneously, add a small amount of solder until the hole fills, and a small amount of solder climbs up the lead (see Soldering Methods for general soldering advice) |
 Step 6: Clean off any excess flux, and examine your work - the solder should be neat and smooth around all of the leads of the SIP. If you spot any balls of solder or holes which do not appear filled, resolder that lead now, to save yourself debugging hassles later. |
Attach the Enable Cable to the Winford Board
Note that amplifier enables require firmware version 3.
In this step, you will solder the amplifier enable cable that you made earlier to the Winford breakout board.
 Step 1:Flux the stripped and twisted end of the enable cable, and solder it in one of the plated through-holes (PTH) labeled 'X1' on the Winford board. The four PTH's for each terminal are all connected to the screw terminal of the same name. 'X1' and 'X2' are the only terminals which do not connect to the DB-25 ribbon cable connector. |
 Step 2:Your attached enable cable should look like this. |
Mounting the Boards
The below diagrams illustrate how to mount the boards onto the back of the Model 1 base.
Electronics Picto-Schematic
This schematic illustrates the connections between the various electronics boards and other components of the Fab@Home Model 1.
Visio Schematic
Current Version
- Link: Model 1 Electronics-05042007.vsd
- Version: 5-4-2007
- Date: 14:16, 4 May 2007 (EDT)
- Platform: Windows 2000/XP/2003
- Format: Microsoft Visio XP/2003
- Size: 300kB
Previous Version
- Link: Model 1 Electronics.vsd
- Version: 3-28-2007
- Date: 13:36, 28 March 2007 (EDT)
- Platform: Windows 2000/XP/2003
- Format: Microsoft Visio XP/2003
- Size: 300kB
If you want to use tool limit switch (U axis), the electronic scheme is below (Contribution from The Renato Archer Center of Information Technology - CTI, Campinas, Brazil)
Commisioned: July 18, 2008.
In the case of the limit switch of the active syringe is active during a printing, the applications immediately pauses the process allowing you to recharge the syringe. Then you can hit Resume printing and the machine will continue the process of building the object.
Picto-Schematic
This schematic illustrates the connections between the various electronics boards and other components of the Fab@Home Model 1, 1 Syringe System with U Limit Switch.
Cable Attachment Images
 Here's how the ribbon cables look when attached to the LPC-H2148 and the Winford board. |
 Plug the enable cable jumper ends into the ENABLE (J?) header (white, between TB-AUX and J7). Leave the pin closest to TB-AUX unconnected. |
 Here is a closeup of the limit switch connections. Note that for each limit switch, one of the wires will be connected to the ground terminal at the bottom of the Xylotex board. Depending on the gauge of your limit switch cables, this bundle may not fit into the screw terminal. For this reason, it is recommended that you "pigtail" these limit switch conductors together - solder them all together, and then solder that bundle to a short piece of wire. Shrink tube the solder joint. This arrangement will make a more reliable connection to the screw terminal for the limit switches. |
|
 Here's a view of all of the cables connected, and the electronics mounted on the back of the machine. |
Electronics Pinouts
Full electronics pinout and pin assignment information: The below Excel workbook includes several sheets that describe the pin assigments and cable connections for the various electronic components. Please use this as a complement to the Schematics and the User Manuals and Board Schematics
Current Version
- Link: Model 1 Pinouts-05042007.xls
- Version: 05042007
- Date: 14:16, 4 May 2007 (EDT)
- Platform: Microsoft Excel
- Format: Microsoft Excel XP/2003
- Size: 296kB
If you want to use the tool limit switches U and/or V axis (Contribution from The Renato Archer Center of Information Technology - CTI, Campinas, Brazil)
Commisioned: July 18, 2008.
The electronics pinout and pin assignment information is below
In the case of the limit switch of the active syringe is active during a printing, the applications immediately pauses the process allowing you to recharge the syringe. Then you can hit Resume printing and the machine will continue the process of building the object.
Current Version
- Link: Model 1 Pinouts - 1 or 2 Syringes with U and V Limit Switches.xls
- Version: 07182008
- Date: 11:40, 18 July 2008 (EDT)
- Platform: Microsoft Excel
- Format: Microsoft Excel XP/2003
- Size: 338kB
Navigation
- Buy tools required for assembly
- Choose your style options
- Buy the parts for the Model 1
- Build the cables and subassemblies
- Assemble the subassemblies into the complete Model 1 System
- Assembling the Chassis
- Mounting the 1-Syringe Tool
- Preparing and mounting electronics
- Program the LPC-H2148 with the Model 1 Firmware
- Install the Fab@Home Model 1 Application
- Commission the Model 1
- Use the Model 1
