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Herbert 1701 Species C Generations 1 & 2

Sensors are a very import biological component and yet they are something that get skimped upon when it comes to the field of robotics. Skimped upon not in terms of cost, but more in terms of volume. This does not pertain to the current evolutionary cycle of Herbert; it is just something I wanted to mention. I promise I will get back to that gripe at some future date, for now we have a new species of Herbert to uncover.

The addition of Herbert's first two little sensors has opened a whole new world to the poor little critter. Where once there was only darkness, now there is darkness and light (and a bunch of shades in between). What's more, it is a focused light; the very light spectrum that breaths life into Herbert. This new found sense should logically be used for something, and in the very simple organisms that have been the Herbert 1701s, it can be.

Herbert 1701C-1 SchematicEnter Herbert 1701 Species C Generation 1. Now that we have previously determined which came first (that being senses), Herbert has been able to evolve into that which came second: movement. Gone are the trademarked (and traditional) green LEDs of Herbert past; replaced with the simplest robotic form of movement: the motor. Biologically, the wheel is something that is far from simple, but when it comes to electromechanical life the wheel is where it is at.

Herbert 1701C-1 Breadboard
The bread board version of Herbert now seems to lose something once movement has been added, however it still serves as a suitable test bed for initial circuit layout. It also shows us the basic function of Herbert Species C Gen 1; the more light each sensor receives, the faster the corresponding motor turns. Pretty simple, yet a little on the inefficient side.

Herbert 1701C-2 SchematicThe phototropic world is a very energy unfriendly one. Sunlight provides a source of energy to life forms each day, but pound for pound it is not high on the scale of power level. This would be one of the reasons you do not see many trees walking around (there is that one oak, but besides him, not many trees at all). With the addition of the ability to move comes the additional need to not only make the most efficient use of the energy Herbert has, but also to conserve a little more of that energy. Herbert 1701 Species C Generation 2 accomplishes this task through the use of a few different components.

Herbert 1701C-2 BreadboardThe first change is in the value of R2, up from 740K to 820K resistance. This changes the activity voltage range for Herbert to an "on" value of 3.24V and an "off" value of 2.09V. Only a slight increase in voltage as a result, but for bringing a motor out of a stall condition during startup, it helps. In case you do not know, a stall condition is the state where the motor is not turning. Because of Newton's silly little laws of physics, an object at rest tends to stay at rest. This means it takes a little more oomph to get the wheel turning. It also means that once the wheel starts turning, it takes a little less energy to keep it going along. Wasn't that fun and interesting information?

Speaking of stall conditions, because you didn't just get more information than you needed, there is a second changed out component in Gen 2; the primary capacitor, C1. The value of C1 was increased from 1000uf to 4700uf, giving Herbert around 4.7 times more energy reserve to help avoid those pesky stall conditions. It also means it will take Herbert a little longer to fully charge up that capacitor before his brain turns on and says "We have energy, let's roll out!"

The last difference between Generations 1 & 2 is the transistors. As previously mentioned with Species B Gen 2 & 3, the transistors used in a circuit can make a difference in the circuit's efficiency. Herbert 1701 Species C Gen 2 takes this one step further. Gone are the 2N2907 and 2N2222 BJTs, replaced with ZTX968 and ZTX1047A BJTs, respectively. The replacement transistors provide for much greater efficiency under low voltage conditions than any of the previous transistors the Herbert species made use of. David Cook did a complete comparison in his Bipolar Transistor H-Bridge Motor Driver article. The results of his testing were actually a huge eye opener, but you can read all that for yourself.

With the completion of Species C Gen 2, Herbert is getting closer to something that more closely resembles the common views of biological life. Herbert is also getting closer to a critter that I will actually be building out, as opposed to merely bread boarding. Not quite there yet, but soon it will be. And then there will be nothing that can stop Herbert! Muahahahahaha! Ahem. Sorry.


I Am. When? on : Robot Sensors

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Spend enough time around robot hobbyists or their message forums and you will come across the two "How Do I" topics that popup over and over again. It depends on the time of year and climate as to which topic is more popular, but the first is &


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