I love the idea of using a 5v micro controller to control my 110v 10 amp outlets. My only concern is the high voltage frying my board and burning my house down. Any thoughts?
You might want to look at the schematic and design layout of the Power SwitchTail II for ideas, as well as what TK Boyd presented. I do a fair amount of controlling mains current, and typically use these. Very simple - three inputs: power, ground, and optional signal. It would likely be too expensive to use eight of them, at $20/unit; but it would show you how to safely isolate mains power up to 15A. I would wonder how well the above board would even work with 10A on eight small terminal blocks shoved that close together with variable loads. Sounds like a recipe for a fubar from all the induction.
You are wise to be careful before connecting to 110v AC, with a voltage source capable of supplying many amps.
It CAN be done... but do be careful. If you have a fire, your household insurers may well worm out because of the "unapproved" (i.e. no UL approval) devices knowingly hooked up.
Loved your picture the "don't do it" option!
I've written more thoughtfully on the subject at...
One of the biggest issues for any 'mains control' is providing isolation between the 'Mains' voltage (high voltage) and the 'control' voltage (low voltage).
While the design appears to have optical isolation between the input and the relay coil, there is very little 'physical' isolation between the coil voltage (supply or common) and the controlling voltage pins. (single header)
Unless the board has a cut in the fibreglass around the contacts, under some circumstances the mains voltage can 'track over' to the relay coil pcb trace or control traces.
(433Mhz controlled mains outlet showing the cut in the pcb for mains isolation ..... photo by me)
Not only does this render the optocoupler useless, potentially you could have mains voltage present on a control wire (or supply or ground).
It's unlikely to trip or blow any circuit breakers as the controlling device is usually fed from a floating power supply.
These relay boards also lack an earth plane which can provide a current path for any 'fault currents' to trip the circuit breaker.
Often the pcb trace size is not adequate for 10A, which may simply cause the trace to part/blow or at worst cook the pcb (modern pcb designs should not support combustion ... but do you really know.)
So the reality is they are only suitable for controlling low voltages in their present configuration DESPITE THE RELAY RATING.
If I had to use this board for this purpose I would put individual 24 volt contactor relays on each outlet line in proper code enclosures and use the relay shield to switch the 24 volts needed to drive the contactors.
Fully agree! This is how I ALWAYS approach interface with mains electricity. I would highly recommend keeping the relay interface card in a separate enclosure and running 24V cables into your contractor housings.
This drastically reduces the chances of a stray mains wire from making contact with your arduino/touchscreen/fingers.
Hi Zachary, Without knowing your experience level I would definitely approach this with caution and the fact that you ask the question indicates that this might not be a good idea. The board you show has relays rated at 10 amps but they are very marginal for switching house lines. What is to keep someone from plugging in a hair dryer or a space heater? The design of the board also brings the switch main lines into close proximity. Here in the USA mains are split off a power feed with 110 volts on either side of a neutral. This means that the 110 lines are out of phase with each other and actually represent a voltage of 220 volts across them. Unless you are careful you could easily have 220 volts on the relay board separated by a very small distance and held by a header that isn't designed for this purpose. The board looks like it would be fun to experiment with but the voltages that are appropriate would best be under 50 volts and isolated from the mains. If I had to use this board for this purpose I would put individual 24 volt contactor relays on each outlet line in proper code enclosures and use the relay shield to switch the 24 volts needed to drive the contactors. This would be safe and you could increase the current handling above the level of the circuit breakers on the individual lines.
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