A 2N3904 transistor was added to the circuit in order to get more power through the coil and boost the magnetic output. A 2N3906 transistor could have also been used if the circuit were designed to switch on the positive side of the load.
Switching with the transistor improved performance because it was easier to feel magnetic pulses from a heartbeat or an oscillating program. A diode was never added to the circuit to protect the controller and was likely the reason the controller stopped responding. The controller was discarded and a virtually identical replacement was substituted but instead of soldering all the components directly to the board they were divided into two halves.
The first half was the heart sensor and coil which were intended to mount on the finger containing a magnet. Standard header connectors, DuPont connectors, were used because they were stocked and simple to change components.
The second half was the controller and transistor. This half was not necessary to be near the finger so the bulk could be moved closer to the battery. Previously the transistor stood far out from the controller but this time the leads were covered in shrink tube and the transistor was held close to the board.
Both halves were easily connected with long header pins or DuPont wires and each time they tested well. The wires had stiff insulation and the sockets wouldn’t hold the pins tightly. This combination means the final product will need flexible wires soldered to the components in order to be viable.
The rest of the posts for this project have been arranged by date.
First time here?
Completed projects from year 1.
Completed projects from year 2.
Controller, transistor, and coil
Switching with the transistor improved performance because it was easier to feel magnetic pulses from a heartbeat or an oscillating program. A diode was never added to the circuit to protect the controller and was likely the reason the controller stopped responding. The controller was discarded and a virtually identical replacement was substituted but instead of soldering all the components directly to the board they were divided into two halves.
The first half was the heart sensor and coil which were intended to mount on the finger containing a magnet. Standard header connectors, DuPont connectors, were used because they were stocked and simple to change components.
Heart sensor and coil with DuPont connectors
The second half was the controller and transistor. This half was not necessary to be near the finger so the bulk could be moved closer to the battery. Previously the transistor stood far out from the controller but this time the leads were covered in shrink tube and the transistor was held close to the board.
Controller and transistor with DuPont connectors
Both halves were easily connected with long header pins or DuPont wires and each time they tested well. The wires had stiff insulation and the sockets wouldn’t hold the pins tightly. This combination means the final product will need flexible wires soldered to the components in order to be viable.
Both halves connected with long header pins
Both halves connected with DuPont wires
The rest of the posts for this project have been arranged by date.
First time here?
Completed projects from year 1.
Completed projects from year 2.
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2016-02-24 (W)
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