A DIY Ultrasonic Signal Generator for Sound Experiments
  Many physics departments around the world have electronic and mechanical workshops attached to them. The job of these workshops is to design and build experimental setups and instruments for research and the training of undergraduate students.   However, in developing countries such as Sudan the lack of qualified technicians and adequately equipped workshops hampered efforts by these departments to supplement their laboratories with home built equipment. The only other option is to buy needed equipment and experimental setups from specialized manufactures. The latter option is not feasible the departments in developing countries where funding for education and research is scarce and very limited as equipments from these manufactures are typically too expensive.   In the past couple of years and with the advancement in prototyping tools like Arduino, and microcontroller development boards, more friendly programming languages, 3D printers, desktop CNC machines and easy to use CAD/CAM softwares the need for highly qualified technicians and expensive workshop equipment was then relaxed \cite{nature-flypi}. The availability of such affordable, and relatively easy to use tools had the effect of increasing the number of teachers and researchers willing to develop their own experimental setups\cite{polis-flypi}.   During the past year and motivated by the need to equip our laboratories with new setups we established a small workshop at the Department of Physics for developing experimental setups to be used in our undergraduate laboratories. The ultrasonic signal generator we are describing here is one such equipment. 
Ihab F. Riad
physics.ed-ph