Blog 26d. Trying to satisfy the electronic expansion requirements 6.I. - 6.K.

This is the last page of requirements being newly captured, which are object for solution alternatives. Maybe you think that it is quite unnecessary to propose such big amount of alternatives to such many requirements, just for to provide some simple electronic equipment for an outdated caravan.

But these requirements are good examples on how seemingly simple requirements, may end up in many complex and alternative solutions.

Requirement 6.I. specify that the audio source (phone, tablet or laptop) must be charged all the time, during it is used to play back music. Modern such devises only have one input/output connector to serve both power input and audio output. What is most problematic is that the connected device must be able to feed enough current, to run and charge the connected audio source (most power consuming is a laptop). The chosen solution is to use strong USB-C output device, which in turn feed a strong input/output hub connected to the audio source via an USB-C connector.

Back to home page

Requirement 6.J. specifies an outer antenna to the GPRS router, feeding the caravan wifi network.

Requirement 6.K. is the most tricky black-box requirements of them all. Ground loops are generally a big problem in all audio equipment, since they catch up 50 Hz hum from all nearby 230 Volt electricity equipment, and inject this hum into the audio signal flow, causing the loudspeaker to reproduce this disturbing noise. When using modern power electronics, this phenomenon get even worse, because such equipment contain transformers using switched technology. The switch frequency is quite high and inaudible, but if there are many such frequencies with quite similar frequency, the difference frequency become quite audible and very disturbing in the loudspeakers.

To chose a good enough solution to avoid ground loops, an activity step back to prototyping was necessary, to order more samples from suppliers, and experimenting with them in different circuits, see next blog #27.