[02-MAY-22] The Direct Fiber Positioning System (DFPS) Backplane (A3044) consists of a long, rigid circuit board into which we plug multiple service boards, such as the DFPS Base and Service Board (A3043).
The service boards in turn receive the controllers for the positioners in the cell. The base board and service board are one assembly connected by flex cables. The backplane proviodes power and logic control signals to all its cells.
The backplane will provide three connectors for service boards, as well as connectors that deliver ±250 V to the system for electrode drive, 2.4 V and 1.2 V for logic and conversion, and SDO and SDI for communication with the fiber controllers.
The following versions of the DFPS Backplane (A3044) are defined.
|A||A3043||3 × 1 with 20-mm spacing||Backplane for 4×4 cells.|
The DFPS Backplane (A3044A) provides connectors for three DFPS cells. Separate regulators provide 2.40 V and 1.20 V for the fiber positioners of each cell. A shared +5V power supply enters through a four-way connector on one end of the backplane, along with Serial Data In (SDI). A shared Serial Data Out (SDO) line leaves the backplane through the same connector. A larger four-way connector on the other end of the backplane brings ±250 V to the cells.
Drawings and other design files below.Mechanical Drawings: Drawings of three 4×4 cells on a frame mounted to on a two-axis gimbal.
[20-DEC-22] The A304401A needs the following modifications on its way to becoming the A304401B.
[18-JUL-22] We have the bridge plate mounted on our Test Stand Two, ready for the backplane.
[13-OCT-22] Backplane connections and power supplies designed, schematic S3044A_1. Printed circuit board outline and connector locations fixed. We will be using 50-mil pitch two-row, ten-way headers and sockets to hold the service boards to the underside of the backplane. Regulators will provide 2.4 V and 1.2 V to the service boards, one set of regulators per service board. For the logic power supply and communication we are going to try out the PZN hermaphroditic connectors from Omnetics, a four-way surface-mount vertical connector on the underside of the backplane. We will glue it in place and see how well it lasts. We will use a mating part with wires soldered to its pins. These wires will run to a Command Transmitter (A3029C), which will provide command transmission through SDI to the fiber controllers on the service boards, as well as 3.3V or 5V power for the backplane regulators. We use the TPS70912DBV to provide 1.2 V at up to 150 mA, which is enough to blow the 50 mA fuse on a fiber controller if there should be a fiber controller short of 1V2. We use TPS7A2024 to provide 2.4 V for 2V5. The logic power supply VL on the backplane can be anything from 3.0 V to 6.0 V.
[17-OCT-22] Ordering A304401A PCB for backplane.
[20-DEC-22] Assemble our first A3044A. Loading P2 we note pad rows too close together, but we are still able to make joints. In loading the connector we choose the orientation for future assemblies. We have PZN-04-WD-18, the same connector with 18-inch leads. If we rotate the connector we end up with black for +5V and red for 0V, which goes so against traditional color assignments that we prefer the mixed-up colors of below.
[21-DEC-22] We connect 5V power and SDI to our A3044A using our PZN-04-WD-18 cable harness. We see 2.4 V on 2V5 and 1.2 V on 1V2. We connect a base and service board A3043A and into the service board we in turn plug a fiber controller A3045A. The fiber controller is running fine. We have tested all connections except the high voltage. The fiber controller receives and responds to serial commands received through P2.
[30-DEC-22] We rip P2 off the board: solder joints break. Apply black DP270 epoxy to hold it in place.