Possibly the simplest circuit in terms of components required, this uses only two transistors in an astable multivibrator configuration. This circuit will not be terribly accurate with the frequency it produces due to component tolerances (1% - 5% on resistors, 20% or more on the capacitors, plus potential mismatch on transistor current gain). Fortunately, accuracy is not critical here.
Values were determined using a simulation program called LTSPICE - which is usually pretty accurate - and the values used here generated a 5V square wave with a frequency of 310Hz. Rearranging the formula derived in post #1, this should correlate to a speed of approximately 114mph.
The transistor choice is not critical, any generic NPN transistor will do, although the BC547 is the defacto standard in my region. American viewers will likely have the 2N2222 or the 2N3904, both of which are suitable replacements. Resistors can be either metal-film (1% tolerance) or carbon-film (5% tolerance) and can be of any power rating. Capacitors should be non-polarised, the most common type fitting the requirement are ceramic capacitors; any dielectric and voltage rating is suitable here. Finally, the regulator choice is also not critical, either a 7805 or 78L05 (L standing for
Low power applications, compared to the standard part) will work just fine. You may be able to get away without using the capacitors C3 and C4; however, if the 5V output is not stable for whatever reason, the capacitors C3 and C4 should fix this issue.
Alternative Link:
https://drive.google.com/file/d/1GZ2...usp=share_link