Concept
Here is nothing special: we have three external inputs and one internal input (from the phone amplifier board). All digital connectors exit twice to have the possibility to loop through. The relays have to be signal types (with gold-plated contacts) because signal relays don't need a minimum current (in contrast to power relays).
Hardware
I'm using HFD3/5 relays of the Chinese company Hongfa. Alternatives are:
- Fujitsu NA5W-K
- Omron G6S-2 DC5
- NEC EC2-5NU
The whole KiCad-project (including Gerber-files) can be found here. Remark: it was made under Linux with KiCad-version 4.0.7 using this additional libaries. The bill of material (bom) as semicolon separated text file contains some comments about part dimensioning / quality.
License
Please keep in mind: all content on this page is licensed under the terms of the GPLv3.
falk.richter*at*yandex.com
Last update: December 20, 2019