as above.
to make sure everything works, I tried a spare 100VA transformer and it's working as expected. Obviously, that' overkill for this use so I'm wondering what's the minimum I can use.
quick glance looking at the main parts
datasheet list:
to make sure everything works, I tried a spare 100VA transformer and it's working as expected. Obviously, that' overkill for this use so I'm wondering what's the minimum I can use.
quick glance looking at the main parts
- a bridge rectifier of unknown make/model (markings D4A60)
- 1x 7812 regulator (tracing the PCB, the output is sort connected to the other end of the relay coil (all 8 relays) via a diode)
- 1x 7806 regulator (The ADC0804 below has a max voltage of 6.5V. it's a good guess that this chip is powering that)
- 8x Omron G6S-2-12v (looking at the datasheet, the rated current on Page 2 for this model is around 11.7mA)
- 1x ULN2803APG (8ch Darlington Sink Driver - looking at the PCB trace, its output is connected to one side of the relay coil)
- 1x ADC0804 (pins 11 to 18 are connected to the input of the ULN2803APG)
datasheet list:
According to the datasheet that says 12mA (roundind) for 12V coil, and having 8 units, total relay load is 96mA. Add 100mA more for logic, a 12V 200/250 mA unit is sufficient.
I’d go to half an amp AC. 1.4 X for capacitor input filter, and another 1.2-1.6 X for power factor, on a 200-250mA DC load. If all the relays are on, the continuous load can be “high”, unlike the amp where it’s more intermittent. A lot of times, something convenient like a 1-amp might be the cheapest anyway.
You could check if you have an old wall wart that would work. I am using a linksys router one (12v@.5A) for my attenuator. 8 relays can be on at once like yours with a similar coil current requirement.
just found a spare adapter (12V@2A). great suggestion/alternative to using a transformer.