After plenty of discussions and investigations, we finally developed Device 4. 0 (Figure 1）. The introduction of previous generations of the Device is described in detail in the device history page. Different from the previous device, we added a structure called filter wheel to both the emitted light path and the incident light path. Each filter wheel is equipped with four different filters, and the filters on the two filter wheels correspond to each other, forming 4 pairs of filter groups, which can respectively excite four different probes. So we can detect the luminescence of different probes in one system and then judge how many viruses are in the system.
Figure 1. The 3D Demo of final Device
From left to right: light source and heat dissipation system, LED partition, filter turntable 1, steering gear and light barrier 1, sample fixing plate, sample plate, sample partition, filter turntable 2, steering gear and light barrier 2 , Silicon light tube and micro voltage amplifier, back cover. Except that the sample partition is white, the rest are all black. We jokingly call it an "Oreo".
The wavelength for each set of filters and the corresponding fluorescein are listed in Table 1.
Table 1 Parameter (wavelength) for each set of filters and the corresponding fluorescein
The device made for the first time was shown in Figure 2. It is rough and based on a paper box. In the actual test, we found many problems. The most serious one is that the light leakage is very severe in the entire light path.
Figure 2. The device made for the first time
After constant debugging, we made out the second-generation device, which looks more mature and more powerful than the first-generation one. On the front of the device, we added a screen, which is convenient for users and professionals to read data and debug the device. Because this is a prototype of the final device, so we did not encapsulate the product so that the various wires would look messy. There is an SD card module on the left side of the device, which can be used to store the read data in the SD card. After that, the SD card can be inserted into the computer and the data can be read with software on the computer.
We can see most of the parts of the device through the top view. The shell of the device is mainly made of discarded cardboard, and there is a single-chip microcomputer main board on the top, which is the control center of the entire device. This whole device can be powered by a battery, thus achieving portability. During the debugging phase, there is no cardboard covering on the front of the device, so we will add a cardboard covering on it after the debugging in order to completely isolate the inside stuff from the outside light.
Figure 3. Our final installation
Figure 4. The low-light sensor & Fig 5 Circuit diagram
The low-light sensor ( Figure 4 ) consists of a silicon photovoltaic cell and a micro-voltage amplifier. The voltage of the silicon photovoltaic cell will increase with the increase of ambient light intensity, and it has high sensitivity. After the voltage amplified by the amplifier, we can transmit its output to the microcontroller as an analog signal.
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