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Herbert 1701 Species B Generation 1

The previous species of Herbert 1701s have all made use of a Miller Solar Engine, thanks to its simplistic design and low level of parts required. There are other solar engine designs that would work about equally, some better, some worse; it just depends on the application and part availability. If you have an interest I would encourage you to take a look at the variety of different solar designs at solarbotics.net.

There is one problem with the majority of solar engines out there, including the Miller SE, and that is the lower voltage levels that each handles. A portion of the SEs make use of the 1381* chip to determine the turn on and turn off voltage levels, which requires replacing that chip with a different 1381* to raise or lower the "trigger" level. Despite that, the base voltage levels for the 1381* designs remain quite low. Other designs use various diode combinations, again producing lower voltage levels. There are methods of increasing the voltage trigger level for most of these designs to higher levels and perhaps we shall delve into those during a revisit to Species A, but for now it is time for a new species to emerge.

The reason a higher voltage trigger level is desirable at this point is the need to allow for further growth and evolution. Many components exist and can be used that would work fine in the 3V range, but if something requires more power it can be a problem. To that end, we will evolve our existing Herbert to a new species, one that possesses a different style of SE at its heart; the Maxim MAX8212 Voltage Monitor.

The MAX8212 can be used in solar designs similar to other SEs, at the cost of additional resistors to the circuit. The benefits of the MAX8212 are a lower power consumption (compared to many other voltage monitoring SEs) and the ability to vary the voltage trigger level by varying the resistors. Both of these things make sense from an evolutionary stand-point; energy efficiency is a highly desirable genetic trait and if a life form is to continue to evolve and grow, it will require more energy to handle the various systems that take shape. After all, what would be the sense of developing a tail to swim with if the fish lacked the energy to move it? That species would die off pretty quickly.

The basic design around a MAX8212 Solar Engine is simple; three resistors are used between power, two pins and ground. The two pins are Hysteresis output (HYST) and Threshold (THRESH). The other pins involved are power (V+), Ground (GND) and Output (OUT). In a nutshell, the three resistors flow energy from the power source to ground, across HYST and THRESH, and as the laws of energy would have it, they drop the entire voltage level down to nothing in the process. The magic happens based on how much of that voltage each resistor drops along the way.

By varying the resistor values, we can set how much voltage hits each pin for any given supply voltage. A spreadsheet to determine these resistor values can be found here, as well as a little schematic showing where they go. The MAX8212 contains a self regulating 1.15V reference source and a comparator. When the voltage on the THRESH pin hits 1.15V the comparator notices this and sets the OUT pin to a low level. This low level will remaining active until the supply voltage drops down to a preset amount. The preset amount is determined by what is going on at the HYST pin and, by a strange coincidence, the voltage level sitting at the HYST pin when the THRESH pin hits 1.15V happens to be the turn off voltage (Vl). Basically it is magic.

You can use the spreadsheet to determine the resistor values needed; just enter the On Voltage (Vu), the Off Voltage (Vl) and first Resistor (R1) Value. The Maxim datasheet recommends an R1 value in the 10k ohm to 10M ohm range. Higher values are better as they allow the circuit to consume less current, but too high can result in insufficient current for the comparator to use. It is a balancing act.

Using the base MAX8212 design, we can combine it with most of the same components used in Herbert 1701 Species A Generation 1, merely replacing the voltage trigger with the new MAX8212 trigger, and replacing the transistor with a PNP type transistor to create Herbert 1701 Species B Generation 1. The schematic shown depicts the finished design for this species of Herbert, with resistor values that will turn the circuit on when the capacitor charges to around the 3.15V level and turn it back off when it drops down to about the 2V level.

With Herbert all built out into a solder-less breadboard we can see the new AL in action. Drum roll please. In light, the green LED illuminates and Herbert expends energy. Pretty similar to our previous Herbert species except where Species A would flash the LED as the circuit charged and discharged, Species B stays lit under the same conditions. This is because of the greater efficiency of the MAX8212 SE design, which I believe I mentioned previously. While the new species does very little that is new, it is a more efficient design and will allow for better, stronger, faster and prettier generations to come. And that is what evolution is all about.

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I Am. When? on : Herbert 1701 Species B Generations 2 & 3

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As noted with the release of Herbert 1701 Species B Gen 1, species B is an improvement over species A in the area of efficiency. A good chunk of this improvement is in the form of the MAX8212 Solar Engine versus the previous Miller SE, but you might also

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