Posts tagged: Maker
Mar 07 2012
This diptrace schematic is a minimal circuit using the TPS62056DGS voltage regulator. It also depicts a momentary pushbutton switch as a holdover from the previous revision.
Beau Schwabe, IC layout engineer and member of our local Ohm Space, revised a circuit he designed years ago to work efficiently with my regulator board. He built a proto pcb with this circuit on it and I am currently testing it with my regulator. He has taken up the challenge and is working on an even simpler design that will reduce component count and cost, and will increase power efficiency. We are moving towards a simple elegant solution that will exceed all the design specifications and yield a unique and highly flexible solution for breadboard power supplies and beyond.
Mar 01 2012
Today I populated another regulator PCB, leaving out the components that won’t be in the final design. The standby current at 6v input level is now only 1uA! My latest estimate of the quiescent current of the toggling/control system is ~50uA. I’ll refine my numbers as testing verifies them. I’m considering placing the pads for, but not populating the indicator LED in the final design so as to save a few milliamps, but on the other hand, one could always remove the LED or cut a trace.
I just tested the quiescent current of my prototype circuit, minus the indicator LED, and it is 38.6uA! With no indicator LEDs the current jumps to 1.9mA while the button is being held down.
Feb 28 2012
Here is the toggling circuit I am working on as represented in the iCircuit iOS simulator. Here I have my 3.3v switching regulator (TPS62056DGS) represented by an op amp with a reference voltage at 1.3v. I am representing an input pin of a 3.3v microcontroller with the second op amp.
This circuit works as follows: The when the switch is closed battery current is conducted through the 1k resistor and the diode into the enable of the voltage regulator. When the voltage reaches 1.3v the regulator switches on, outputting 3.3v and powering up the flip flop and other circuitry. The flip flop powers up in its default/unset state holding the regulator enable high with its Q’ output. The button is released and the clock line goes low. The diode prevents the flip flop output from holding the clock high (only a rising edge clocks in the output state bit). Upon the next rising edge of the button press the flip flop clocks a 1 into the Q output making the Q’ output 0 disabling the regulator and shutting itself down.
The transistor circuit allows a uC to read the inverted state of the button press. Not shown in this circuit are the asynchronous flip flop inputs needed to lock the output so it does not toggle while the microcontroller is monitoring button presses, and the input allowing the microcontroller to shut down the circuit. I plan to use the 74LVC2G74DP,125 flip flop, but as mentioned before the circuit is prototyped with another one.
The standby current of this circuit is less than 4uA, and the power efficiency at 100mA load is about 90%.
Current design specifications summary:
Feb 24 2012
Have you ever finished breadboarding a project and upon reviewing your work observed that a large portion of your breadboard space was being wasted by your voltage regulation system?Have you ever wanted to use switching regulation in a high efficiency low power project? I do all the time, and I started working on a solution to this problem not too long ago. It started out as a breakout board I was designing for the purpose of prototyping a power supply circuit in our pan tilt zoom camera system. The requirements for the PTZ camera board were: switching voltage regulation, 3.3v output (for my beloved Propeller microcontroller), an input range suitable for use with 4 AA batteries, and a single momentary push button switch for turning the system on and off. As I lay out the circuit in Diptrace I got to thinking that since I was doing all this work already, I might as well make the PCB useful for other projects as well, so I designed the board with a breadboard friendly row of pins for use with a header strip.
After changing a resistor value the board functioned perfectly (I was being a little overzealous on power conservation and specified a pullup resistor that was too weak). Well, it regulated voltage perfectly and the low battery indicator circuit worked great, but I still had some work to do when it came to interfacing with the Propeller chip. Nathan helped me find the right resistor combination to use to allow the Propeller microcontroller to correctly interface to the button monitor circuit and the regulator enable circuit. It would appear that when a Propeller is powered down the ESD protective circuitry creates a path to ground through the input pins. This presents a drain through an estimated 10K ohms to any circuitry connected to a powered off Propeller pin.
Once the circuit was debugged I had a momentary push button switch that controlled power to a Propeller microcontroller. It functioned as follows: I hold down the push button supplying power while the Prop boots, once the Prop boots it takes over the task of keeping the regulator enabled, if I press the button again the Prop is monitoring the input and can act on my button presses, if I press and hold the input for x amount of time the Prop shuts down the regulator thus turning itself off. The behavior is similar to a computer where the same momentary push button turns the power on and back off, but the computer itself can also power down and theoretically prevent the user from powering off in situations where a hard shutdown would damage hardware or corrupt data.
After getting a taste of the potential usefulness of the regulator board we decided to go ahead and develop it into a standalone product. The design parameters are: full standalone operations (toggling is accomplished with an on board flip flop rather than an external microcontroller), optional microcontroller power override (ability to lock power on or turn power off), optional microcontroller button monitoring, a flexible power input port for various physical connection options (a pigtail with a PCB style connector on one end and a barrel plug, screw terminal block, bare wires, etc. on the other), and perhaps a power indicator LED on board. Of course, at this stage in the design, anything is possible!
I finished a mostly functional prototype of this new and improved regulator board concept today. I had to dig up an old obsolete flip flop I had thrown out, but I did manage to get most of my design ironed out with it.
Feb 24 2012
Most things have a beginning. Well, if one considers the vast expanse of the nonexistent, assuming it does not exist in some alternate dimension, there are many things that never had a beginning. But, this all hinges on the definition of “thing” which may well intrinsically require existence. The act of bringing a “thing” into existence, unfortunately for us mortals, rarely is just a simple “act.” We struggle to define the “thing” we want to create. We arduously prowl through the archives of human accomplishment in search of those foundational concepts upon which to build our new “thing.” We fight with parts and prototypes, striving to arrive at the performance defined in the beginning. We are tempted to redefine success as “what we have right now.” But, we are never satisfied with the present state. We want perfection. We want existence. We want to create. This insatiable desire to create is coded into our DNA. We cannot leave well enough alone. We will never be satisfied with mere conformity. We are builders, makers, inventors. We build because we were built to build.
Oklahoma Robotics was started as a way to practically realize this drive to create. We make it our business to birth these brainchildren that so many are content to coddle in their imaginations alone. We want flesh and blood (so to speak) robots, real autonomous mowers that keep our yards maintained, useful automation that simplifies our daily lives, electric cars made by the people and for the people of the U.S.A., we want alternative energy without the politics, we want freedom for American engineers, freedom to invent, manufacture, and market innovative products. Oklahoma Robotics salutes the Hacker/Maker community, the Open Source community, and anyone else bold enough to leave the “system” behind and forge ahead into the unknown realms of technological possibility. We believe in openness and sharing. We acknowledge the millions of scientists who through the thousands of years of human history have recorded and reported their countless findings for us to build upon. As we continue to share our discoveries, our knowledge, our source code, and our passion for perfection with the world around us, we carry on the legacy of those before us.
In the months and years to come I hope this blog proves to be source of both profound design information and inspiration for those looking to create something new.