Blue BioBug: HACK #1
Addition of a light seeking head with override switch to hand controller.

For a simple modification to the existing BioBug product, I have chosen to add a light seeking head. It started out as a simple modification, but the realization of a functional design entailed significantly more work than anticipated. The head addition was chosen because of its non-intrusive nature, such that modifications were non-destructive and the original platform can be easily reconfigured if desired. I was very happy with my first BioBug purchased at $35 and was hesitant to consider tampering with it at all. The effectiveness of the handheld remote was an obvious achievement, and was the inspiration behind this “simple” autonomous override.

I have chosen to incorporate a switch driven by the head motor allowing an override thought the hand remote to generate an autonomous attraction to light. Solarizing the bot is a possible outcome of this addition but the initial intent here is just to allow an autonomous override through the controller, rather than human. It just so happens that I chose light as the motivational drive to design around.

I first identified a functioning circuit with witch to drive the head motor. I used Wilfs SPH (Smart Pro Head) with little modification. I did my own PCB using the little rub off decals to form the pattern. The design was formed to allow the BioBug to operate to its own desire when head is around the central position, and switch the left/right override at the extremes of travel. It was not the easiest thing to do, but a utility knife allowed the PCB to be effectively sized for attachment to the assembly after etching.
Recognizing the versatility of a rotary switch, it seemed like a convenient resource for some ready to use spring fingers for switching due to head rotation. The existing rotary switch PCB was discarded and replaced with my custom PCB allowing left and right switching corresponding to the head movement. I used the plastic housing to keep the barrel with the spring fingers horizontal and clamped at the proper pressure. I placed a clearance hole in the plastic housing and press fit the spring finger barrel for assembly to the motor shaft. I clamped it all together and secured it with adhesive.

After validating the bread-boarded circuits performance, I soldered it up in the freeform, with a little hot glue in potential short areas. With the cable color code recorded for later hookup, I wrapped the circuit up into a tight little brain bundle.

I assembled the etched PCB head to the rotary switch and neck. The attachment of the head to neck was achieved through the utilization of a spring and damper straight out of a Walkman. It is both robust and flexible, but not garneted to be perpendicular to the neck axis at all time; however, it is stiff enough due to the incorporated spring to keep the head within 10-15deg of the horizontal. I attached a length of large gauge copper wire to the head PCB to act as eye stalks to add some versatility to the eyes position for future study.

I was having trouble with the Hysterisis of the head, and by that I mean there was difficulty with a lock onto the brightest light source (the head would shake). To broaden the range with which the head can lock, I add a couple of extra photodiodes allowing a sort of panoramic view. This allowed for a easier lock with very pleasing results; however, I have noticed that with the additional photodiodes there needs to be a dramatic contrast from light to dark to initiate a redirection of the head. This necessity for higher contrast is causing issue because in mild lighting the light can just drift away without redirecting the head. Just say no to a tethered head (if you can help it). I have used a tether between the head circuit and head PCB holding the photodiodes. Well maybe, it’ll work. When the head is on target, all is well. Once the target is lost, so too is the head, and it will swivel around (despite the tether) until it finds another target lock. There have been some brutal strangulations during the testing. A black shroud may prove helpful, but is more than I wanted to do.

The shroud makes me think of an eye socket. The shroud works (but only because the head is light seeking), as long and the ambient light level is much higher than the internal of the shroud. Once the light is low enough, shroud or not, the head spins. May need to add a photo resistor to disable the head in dark conditions. The switch for the controller may help as a motor override as well. If the switch had been + or – I think it could have been incorporated as a motor stop, but there was no measurable voltage across the remote buttons, so for now this will not be a fix.

Head shroud is looking promising. Eye slot reminds me of Ned Kelly (an Australian Robin Hood type), but I’m sure once assembled the resemblance will be absent. The head shroud is constructed of a black plastic bottle, some wiring and hot glue.

I connected the head switch PCB to a battery and some spare LEDs to position (or tune) the spring fingers between the left/right contacts. Tuning the head driven switch is easier in one direction than the other, due to the direction the internal spring fingers lay. I tried to center the eyes as much as possible but I know that however set, it will eventually need to be retuned. I have tried to keep the head mount (that is the tuning attachment point) to the neck as accessible as possible. Leaving the extra length on the head circuit contacts paid off. I was able to tuck it into the “chin” covering the head motor, something I would not have considered on paper.
Now to the final assembly: How to attach the head and hand controller with two extra batteries to the back of the blue BioBug.

Initial assembly areas look promising. I am trying not to consider adhesives, because it will make future upgrades difficult. It may be possible to use some rubber bands to secure the head and remote.

I’m surprised at how happy the head looks. It was not intentional yet compelled me to smile.

Need to add another two AAA batteries. Mounting of the remote to the bugs back will be through the wing attachment slots.
The remote emitter was positioned to allow close proximity to the center receiver on the BioBug. The hole in the controller is a convenient path for the switching wires. The top housing of the remote is just big enough to hold four AAA batteries in their holders. I don’t like adding four batteries to drive the head circuit, but it will not run off three volts and I’m afraid that six volts to the remote will fry it. Better safe that sorry.


Final assembly is coming together. It is not as tightly packaged as I would have desired, but it works. I used a thin sponge material to act as a damper between the hand controller and the bug body with pleasing results.




Performance??
The strength of the bot is enough to carry the added weight of the remote and head without issue. The switch is performing as intended, and aside form a little quiver in the “eyes" when the light is low there are not issues. I await the arrival of spring and the sun to continue tests in the backyard.