TT MIDI-Switcher - Version 2019
Notes for relay switching
Generally all switching is done on the ground side, so the ULN2803 switches to ground.
Not all inputs and outputs must be assigned or used. Unused inputs and outputs are
simply left unconnected.
If voltages other than 5 V are required for relays, the needed voltage can be supplied by the
“extra power supply” on the main pcb (components not included!). It is important that both
the main voltage and the extra supply voltage have the same ground reference, so both
grounds are referenced together. This is shown in appendix 4.
The relay boards shown on the pictures are not included, these can be selected as
required. Possible boards to use are e.g. the following articles:
tbez-010 (double relay PCB)
tbez-020 (single relay PCB)
tbez-057 (single relay PCB, PCB terminal blocks)
tbez-059 (double relay PCB MAXI, PCB terminal blocks)
tbez-058 (single relay PCB MINI, PCB terminal blocks)
Instead of relays, also optocouplers or transistors can be utilized for the switching tasks.
This may require additional circuitry, such as dropping resistors for optocouplers as
example.
Tube-Town GmbH - www.tube-town.net -
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