Digitally Controlled Dual Power Supply

Dual Power Supply

[Kerry] set out to build a digitally controlled dual supply for his bench. He’s already built a supply based on the LM338 linear regulator, but the goal this time was to build it without a linear regulator IC, and add digital control over both the current and voltage.

In part one of the build, [Kerry] explains the analog design of the device. He had an extra heatsink kicking around, which can dissipate enough heat from this linear supply to let it run at 10 A. A NE5532 opamp is used to track a reference voltage, which can be provided by a DAC. The current is measured by a LT6105 shunt sense amplifier, then compared to a reference provided by another DAC.

Part two focuses on the digital components. To interface with the analog circuitry, two MCP4821 DACs are used. These are controlled over SPI by an ATmega328P.

Fortunately, [Kerry] also has his own DC load project to test the supply with.

A constant resistance dummy load design


This constant resistance dummy load has not yet been tested in the real world. [YS] was inspired to come up with the circuit after reading Wednesday’s Re:load dummy load post. That was a constant current load, not a constant resistance load. [YS] started with the schematic for the Re:load and made his changes to arrive at this.

For him the exercise was just to alter the design to achieve constant resistance. He didn’t actually build and test the hardware because he doesn’t really have a need for it. This image was exported from Proteus, which includes a ProSPICE circuit emulator. His slides run through test voltages from 5V to 50V, maintaining a constant 10 Ohm resistance.

When studying this project we needed a little refresher on the different varieties of dummy loads. We found this post very informative about the differences and uses of Constant Current, Constant Power, and Constant Resistance (Impedance) loads.

Upverter 2.0 Launches

Disclosure: I currently work at Upverter

We’ve featured Upverter here in the past. At that time, the EDA tool was capable of collaborative schematic capture. Today, Upverter is launching version 2.0 of their tool which includes many new features allowing for end-to-end electronics design.

Upverter now has a PCB editor, allowing you to manufacture your designs. They are working with PCB manufacturers to make it easy to choose a fab and submit design files. Other new features include a Spice based simulation engine allowing in-browser simulation, and product lifecycle management features to help manage your project’s bill of materials.

When we last looked at Upverter, it was just a tool for creating and sharing schematics. With today’s launch, the tool can be used for designing electronics from start to finish. Since Upverter is free for open source projects, it will be interesting to see how hackers use it.

You can check out a tour of the new features. Any thoughts on using a cloud based EDA tool? Let us know in the comments.

On not designing circuits with evolutionary algorithms

[Henrik] has been working on a program to design electronic circuits using evolutionary algorithms. It’s still very much a work in progress, but he’s gotten to the point of generating a decent BJT inverter after 78 generations (9 minutes of compute time), as shown in the .gif above.

To evolve these circuits, [Henrik] told a SPICE simulation to generate an inverter with a 5V power supply, 2N3904 and 2N3906 transistors, and whatever resistors were needed. The first dozen or so generations didn’t actually do anything, but after 2000 generations the algorithm produced a circuit nearly identical to the description of a CMOS inverter you’d find in a circuit textbook.

Using evolution to guide electronic design is nothing new; an evolutionary algorithm and a a few bits of Verilog can turn an FPGA into a chip that can tell the difference between a 1kHz and 10kHz tone with extremely minimal hardware requirements. There’s also some very, very strange stuff that happened in this experiment; the evolutionary algorithm utilized things that are impossible for a human to program and relies on magnetic flux and quantum weirdness inside the FPGA.

[Henrik] says his algorithm didn’t test for how much current goes through the transistors, so implementing this circuit outside of a simulation will destroy the transistors and emit a puff of blue smoke. If you’d like design your own circuits using evolution, [Henrik] put all the code in a git for your perusal. It’s damn cool as it stands now, and once [Henrik] includes checking current and voltage in each component his project may actually be useful.