Design Portfolio for Michael Dunn

Here are some of my designs from over the years.

	Here's a 486-based comms system I designed around 1997. The left board is the T1/E1 interface. The piggyback board on the right is the eight port high-speed multi-protocol serial interface.
	A high-end, self-powered, bi-amplified speaker.
	A surround-sound processor ca. 2000 that I sold for several years. Very high-quality, and very musical, as opposed to all the home-theatre stuff out there.
	The PCB for the above.
	A 386EX-based comms processor. The piggyback PCB at the top is an ISDN U or S/T interface and encryption processor.
	A higher-end version of the previous unit, the main board is at the bottom. One or two boards can be stacked over it. The one at the upper-right is an octal PPP interface. The upper pair are eight ports worth of network-side U-interface.
	This is an ISDN test system and interface I designed in the early nineties. It can be used stand-alone, or connected to a back-end analog telephone test-set. The chassis and internal 386 PC-on-a-card are off-the-shelf products. I wrote all the low-level (assembler) code for the Z80 system processor as well as some user and test software in BASIC. Four cards were designed for this: The system controller card, including the Z80 and PC interface, the analog card handling data acquisition, signal generation, and POTS interface, the line card, handling the ISDN interface, test and measurement circuits, and programmable power supply, and the line-simulator board, able to simulate a phone line from 0-1500m, controllable in 100m increments.
	This is a full-custom IC ca. 1988 (I designed the discrete-circuit version and supervised the IC manufacturer who did the detailed chip design). It's an "intelligent" 10A solid-state relay (sans MOSFET) for automotive use. There were many stringent design requirements due to the automotive environment. The "intelligence" refers to sophisticated overload protection. A shorted load immediately shuts down the relay, from which it periodically tries to recover. A less severe overload current is integrated over time before kicking in the protection, allowing the relay to handle for example headlight inrush current, while still fully protecting the FET.
	Here is a plot of the custom IC die.
	The finned device is the package for the above SSR. I did the basic design of this too, though I don't claim to be a mechanical designer. The boards on the right and bottom are discrete prototypes of the SSR. The simple board in the middle is a soundcard (well, basically a DAC) - part of a simple HW/SW music system I designed for the PET computer ca. 1980. Ahhh, such memories...
	The "SPC Master" (1988-89), a V25-based portable computer for statistical process control and related applications. I also designed a custom interface that connected to mail-processing equipment.
	A music synthesizer module I designed ~1979. A cool digital/analogue hybrid that can generate either audio signals or envelopes using a 256-sample lookup table. To generate the table, it interfaces to either a computer, or to an XY panel I built (not shown) using four linear pots.
	Parts of an industrial terminal/logging system, 1985-1987. The board on the left provides 16 outputs and 16 isolated inputs. Up to four could be stacked. On the right, a bar-code wand interface, memory expansion, and RS232 and isolated serial network interfaces.
	The above terminal in operation.