Add basic electrical parameters to the readme

[mDubovsky]

Discussed in #7

^{Originally posted by mDubovsky December 19, 2022}
While assembling the whole system you have to search for values in datasheets and calculate other values.
It would be helpful to have basic parameters in readme such as (but not limited to):

• Maximum current draw of the whole module during heavy network load
• Maximum switched voltage
• Maximum switched current
• Min/Max input signal voltage

[pilotak]

Average current consumption is 1W - (0.4A@24V, 0.8A@12V) when no input (outputs don't matter)
1 input consumes 6mA@24V

the highest current is during power-on when capacitors are also being charged peak 184mA@24V for 5ms

[chrismazanec]

@pilotak you probably mean 0.04A@24V and 0.08A@12V? (~1W)

how is the max input current 0.6A calculated then? 14,4W seems too much, is that a mistake?
https://github.com/pilotak/eth-io/blob/v3/stickers/ETH-IO_v3_stickers.pdf

I have a MEANWELL HDR-15-24 15W 24V power supply, 20 relays which take 7W, so wondering if 15W total is enough

thank you

[pilotak]

@chrismazanec yes 1W (0.04A@24V and 0.08A@12V) sorry

How i calculated it - 0.144W*20(inputs) + 4.416W(startup + ethernet stuff) = 7.3W continuous minimum. I tend to use double the amount i need, as when you reaching the top of current source from power supply, the current is limited, its heat is noticable and i don't like pushing it to the limits. But this is only my practice. You also have to take into account the measurement speed...

On your power supply - it depends. If most of the relays will be switched on and you turn on another, the current might be limited and might not turn on. This is because of the coil in the relay (induction load). But that is a theory only, i'm sure it will be fine in real life, even though i would choose 30W (next step in meanwell).

[chrismazanec]

thank you for your reply.

I think in my scenario, I should be OK - I still have 20% power supply capacity left (max ~12W of 15W) even when all relays are on

26 inputs (3.744W), 20 relays (7W)

• startup, all relays off, for 5ms only
  3.744W (inputs) + 0W (relays) + 4.416W (module 5ms peak) = 8,16W

• normal mode, all relays off
  3.744W (inputs) + 0W (relays) + ~1W (module) = 4.744W

• normal mode, all relays on
  3.744W (inputs) + 7W (relays) + ~1W (module) = 11.744W