After a somewhat longer break in December, we met again on Monday in Presence to continue working on our probe in the coming week and to complete it as far as possible. The main focus today was on soldering a first prototype for our board. The microcontroller and most of the wiring will be placed on this board to save space. However, since we were still working on the circuitry for the pump system and had difficulties with the soldering equipment, the completion of the board has been delayed.
Furthermore, we were able to test the recently ordered gas collection bags in connection with the pump system today. Thanks to the support of MediSense , we were able to obtain these special polypropylene-coated gas collection bags as private customers and in smaller quantities. Since it is essential for a precise analysis of the air samples that they are sterile, we first selected three bags for testing purposes and marked them accordingly. When starting the probe, we then use the remaining, completely unused and still sterile bags.
In addition, we directly tried out experimentally how the gas collection bags have to be attached to the outer shell so that they can unfold as easily as possible when inflated. The biggest difficulty here was not to exceed the maximum dimensions described in the requirements. We found a solution to the problem in the use of thin rubber bands, which fix the gas collection bags to the outer shell when unfilled and slip off them when filled. However, since the bags did not lie ideally against the shell during testing and we only had a 3D-printed test cylinder available for the test trials so far, we will have to optimise the concept a bit more.
As already mentioned in the last report, we noticed some errors in the self-test programme of the sensors. For example, it was planned that the readout of a sensor should be aborted if a certain period of time was exceeded in order to prevent the whole programme from hanging up in case of a loose contact. Although we have been able to detect such a timeout so far, we have not yet found a solution to cancel the function for reading out the sensor.