JCA34F:
That type of relay module should be taken off the market, too easy for noobs to blow it up along with their Arduino.
Opto isolated relays should have SEPARATE terminals for coil power and logic, 2 terminals for coil + and -, 2 for signal common and input. And why bother making them active LOW when every noob in the universe expects HIGH to be ON?
+1
Look at that goofy schematic, the way I read it:
If the opto is NOT conducting, the coil is ON and vice versa.
Please note, that was the closest thing that can be found as a schematic for that module.
The only thing that is nice is the option of having HIGH or LOW input triggering but then so what >:( .
Software can make things invert :).
I think someone like member Crossroards should make a properly designed series of these modules available to the world !
1, 2, 4, 8 channel relay module, however, I guess it’s all about price.
He does have this:
Where did you find that schematic, Instructibles ? 
Wouldn't be too much expense to put an extra 2 cent terminal and an Omron relay on what they have but they would have to jack the price up to $3.99 instead of $2.99 so they could say "our relay sells for less than $4.00".
I think it was:
However, the one there has the PNP base going to JD-Vcc :o 
go figure:
“Oh the pain of it all”
Dear All,
I think the reverse kickback diode is less important as both circuits (power-pump and Arduino) are galvanically insulated using the relay.
But it remains advisable, but less essential compared to a situation where both circuits are fed with the same supply.
Best Regards,
Johi.
JOHI:
Dear All,I think the reverse kickback diode is less important as both circuits (power-pump and Arduino) are galvanically insulated using the relay.
But it remains advisable, but less essential compared to a situation where both circuits are fed with the same supply.
Best Regards,
Johi.
We do our best to keep new people from running into problems.
Stopping half way and ‘not’ passing on best design practises is simply poor form.
You cannot count how many times we deal with problems in hardware which results from spurious noise.
No one is quantifying if something is more or less important, a 10 cent diode stops motor noise, full stop.
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