11/3/2017
This week primarily involved circuit design. Early in the week, we communicated with Dr. MacEwan and impressed upon him again how important it is that we hear back from Northwestern about the circuitry components that they feel comfortable fabricating for us. While we were not copied on the email, we are now waiting on a response from Northwestern.
In the absence of feedback about circuitry components, we have begun researching and designing various circuit prototypes. We have been using LTSpice which enables us to design the circuit, and then run tests on it, all completely virtually. The two circuits that we have designed so far are the constant current output circuit with an embedded power supply and the highly resonant wireless power transfer circuit.
The challenge that we are running into with the constant current circuit is finding an accurate way to model the load. We know it will be the resistance between the tip of the bone screw and wherever we place or embed ground, however, the more we think about it, the more it becomes clear that the resistance will not remain constant as the patient changes body positions and perhaps between patients. There is also the difficulty of finding an accepted value for the resistance between the interior of a vertebrae and the ground we will set 2 cm off its dorsal side.
The high resonance power transfer circuit is proving to be quite interesting. Using LTSpice, we constructed a generic high resonance power transfer circuit and can now modify the parameters of the different components. We can then perform an AC input frequency sweep to determine which frequencies have the most efficient power transfer. Our next challenge with this circuit is to replace the AC power supply with a processed DC power supply that can mimic an AC power supply at the desired frequency.
This week primarily involved circuit design. Early in the week, we communicated with Dr. MacEwan and impressed upon him again how important it is that we hear back from Northwestern about the circuitry components that they feel comfortable fabricating for us. While we were not copied on the email, we are now waiting on a response from Northwestern.
In the absence of feedback about circuitry components, we have begun researching and designing various circuit prototypes. We have been using LTSpice which enables us to design the circuit, and then run tests on it, all completely virtually. The two circuits that we have designed so far are the constant current output circuit with an embedded power supply and the highly resonant wireless power transfer circuit.
The challenge that we are running into with the constant current circuit is finding an accurate way to model the load. We know it will be the resistance between the tip of the bone screw and wherever we place or embed ground, however, the more we think about it, the more it becomes clear that the resistance will not remain constant as the patient changes body positions and perhaps between patients. There is also the difficulty of finding an accepted value for the resistance between the interior of a vertebrae and the ground we will set 2 cm off its dorsal side.
The high resonance power transfer circuit is proving to be quite interesting. Using LTSpice, we constructed a generic high resonance power transfer circuit and can now modify the parameters of the different components. We can then perform an AC input frequency sweep to determine which frequencies have the most efficient power transfer. Our next challenge with this circuit is to replace the AC power supply with a processed DC power supply that can mimic an AC power supply at the desired frequency.