Does that sound right? 20amp should just be enough, but would 100w be enough? Is there a better way?
I have tried getting a old laptop power supply thats 15v @ 5amp, figuring if I step it down to 5v, it should be 15amp. I can get it down to 5v, but then it cant even seem to power 1. As soon as I put any load on it, it drops down to 0v. I have tried many different sources, and all the same result.
It's a nice PSU, but you don't need such a heavy one to control the relays.
The switch of the relay is rated at 20AMPS, but the coils of the relays are 1-watt types, driven with 5 volts they only draw 0,2 ampere each.
In theory the PSU should at least be capable of driving 14 x 0,2 = 2,8 ampere to toggle the relays. It's not wise to have a PSU operating close to its limits (heat/fire) though, by multiplying it by two you are much safer.
A desktop-pc is by the way easy to test the relays. Black wire is ground, red wire is +5 volts.
Where is the ground connection to the Arduino? I'd wire the relays in more of a star configuration
from the supply too, rather than one long chain.
Also:
a voltage divider will never work in this application
the circuit draws FAR too much current
Indeed! You pretty much never use a resistive divider for power, only for sensing / measuring,
owing to the massive power waste and total lack of regulation.
It looks like he's using twisted pair network cable, which is usually 26 - 28 AWG depending on how cheap it is. Could he be drawing too much current for that thin wire? Its also not meant to be bent a lot, the inner wire can break without breaking the insulation.
wizdum:
It looks like he's using twisted pair network cable, which is usually 26 - 28 AWG depending on how cheap it is. Could he be drawing too much current for that thin wire? Its also not meant to be bent a lot, the inner wire can break without breaking the insulation.
Correct, it was the only solid core cable the local Jaycar had. Multimeter tells me my ring has connection all the way around.
So, a Ring v's a Star. Does it matter? My wire is Cat6 strands.
I am not an electronics/electrical person so treat my comments with caution;
Domestic AC power is wired in star configurations in the US and in ring configurations in the UK. As a result it is not obvious to me why you should not use either for your low voltage DC application. Indeed you could probably mix the two to make wiring convenient.
However you are using fine wire and its not obvious what distances the cable will be run over. I think you need to look carefully at the resistance of your wire and the current it will be carrying. You don't want the voltage to drop below that required to operate the relays and you certainly don't want the wire overheating.
Some other words of caution; you have been talking about these relays as being 20A relays. In fact they should not be used above 8A as the website states;
There are some pretty beefy traces connecting the relay to the load pins, but the 2-pin terminals are only rated for 8A max! If you plan on connecting a larger load you'll need to solder directly to the board. As always with high current and voltage, play it safe and use you judgment when deciding how much of a load you want to put on a board.
Even at only 8A each your 14 relays could be switching 112A so you probably want to ensure your software is structured not to turn on all the load simultaneously.
Finally you should ensure that the AC terminals on the relays are well enough shielded that fingers cannot touch them.
I'm to the point that if someone can't find a way (Windows Paint, GIMP, etc) to reduce the size of their schematics below 10x screen size, I am not likely to bother.
I will agree on the "Reduce the size of your images" statement, as they are far far too large to be useful.
While a the ring (Aka Serial) connection might work, I would not recommend it, as I imagine it will limit the current draw of your various relays to the extent that some might not engage fully. Instead connect them all in parallel (Star) for a more reliable operation, and possible independent control. Additionally, I hope you are not connecting your AC to your Cat5/6 cable, since I don't think Cat5/6 cable has a good enough voltage standoff for safety. You can use it for relatively higher currents if you solder together two groups of 4 wire each, but I'm guessing that is going up to about 3-4A total. Wire gauges are important for safety. It won't require much, but 30 or 32 AWG (cat5/6 cable) is NOT big enough for 8A (I want to say 16AWG is, but you should double check).
Why do you have the Arduino? What intelligence is it adding to this circuit?
Actually, AC power in the USA is daisy chained. Breaker to outlet to the next outlet to the next outlet to the last outlet. There is a limit on the number of connections via either splice or across an outlet, but I don't recall what it is.
