26_SMT Breakout Boards
Several of the components we have chosen to use for the Helping Hand device are only available in surface mount packages. This means that we won’t be able to test the chips as easily as we could with DIP chips. We still need to use some of the components for testing, primarily the ADC, Voltage regulators, and dsPIC... so I’ve made some simple breakout-board PCB designs in Ultiboard. Once the boards are printed and when the parts come in, we should be able to solder the parts onto the boards with solder paste fairly quickly so that we can test peripheral configurations for the regulators and programming options + peripherals for the ADC.
Mr. Plybon has had trouble getting the new Circuit printing equipment ready to use; if we aren’t able to get breakout boards printed soon enough, we may just use generic parts to simulate our parts’ functionality (our motor drivers are similar to the H-bridge chips in stock in the Circuits lab and there are some switching/linear regulators in stock that we can use; also the DIP PIC16’s in the project labs can be used to run initial motor control & ADC code).
Below in Figure 1 are some breakout boards for the voltage regulators. Each chip is connected to some header pins that are spaced properly so that they can fit into our ELVIS breadboards. The voltage regulators, especially the linear regulators, have fairly simple peripheral circuits. The data sheets provided with each of the chosen regulators provides very good advice and equations for choosing peripheral parts such as capacitors and resistors, so if we can’t print our testing boards out soon enough, we can still make fairly detailed Multisim schematics interfacing the components with the dsPIC and other components.
style="font-style: normal; font-variant-caps: normal; font-weight: normal; font-family: Helvetica;">
Figure 1: 7V & 3.3V Regulator Breakout PCB's
This is the ADC’s breakout board with each of the ADC’s pins connected to headers.
Figure 2: ADC Breakout PCB
(Fig. 3) The dsPIC breakout board is large, but will still fit onto the ELVIS boards. The package has 100 pins, but I might revise the PCB to use double rowed headers that would make the PCB smaller, but would not be able to be plugged into the ELVIS boards. Again, if these breakout boards aren’t able to be made in time for testing our parts before the end of Detail Design, the DIP PIC16’s will be used to run sample code demonstrating our motors being run by the H-bridges, and I/O switches working, etc. The compilers used to create assembly code for the PIC microchips can interpret the same C code for different PIC chips with very little change in the coding.
Figure 3: dsPIC33 Breakout PCB
