- Sat Jul 08, 2017 8:38 am
#68075
I looked at this again and what I see is an LED in series with the octocoupler. I also have my doubts that the optocoupler would need that much current in this kind of circuit. But since they are also using that current to drive the led then I can see them putting a low value resistor in series that would allow that much current.
Because of the led status indicator being in series with the opto's led then there are two led voltage drops to take into account. No problem if you are driving from 5 volts, but at a 3 volts drive there is less comfort room. Of course the module could be modified. Remove the led if it is a problem, replace it with an additional current limiting resistor to keep the current under 12 mA. Or remover the opto as well and drive the transistor (with an additional current limiting resistor on the base) directly from the ESP pins.
What it looks like is that there is the led in series with the optocoupler in series with 200 ohms.
One side of the opto is connected to 5 volts, the other side has 200 ohms and then to the base of the transistor.
Because of the led status indicator being in series with the opto's led then there are two led voltage drops to take into account. No problem if you are driving from 5 volts, but at a 3 volts drive there is less comfort room. Of course the module could be modified. Remove the led if it is a problem, replace it with an additional current limiting resistor to keep the current under 12 mA. Or remover the opto as well and drive the transistor (with an additional current limiting resistor on the base) directly from the ESP pins.
What it looks like is that there is the led in series with the optocoupler in series with 200 ohms.
One side of the opto is connected to 5 volts, the other side has 200 ohms and then to the base of the transistor.
