Grumpy_Mike: You can not use a solid state relay to switch low voltage DC. You need to switch the mains input.
You can switch this with a mechanical relay. When it clicks you should see continuity between the common and the NO connectors. So that is where you wire up the break in ONE of the wires of your charger output. You seem to have broken both wires.
Correct... and allow me to elaborate as to WHY this is:
A solid state relay uses an SCR or a TRIAC as the switch. Both of these devices, when triggered, latch on even when the trigger is removed.
They work on AC circuits because the AC power swings through 0 twice for each sinusoidal cycle. When the power swings through zero, the SCR or TRIAC has no current through it to keep it latched, so it "unlatches" (that is, goes open again).
If the trigger signal is PRESENT, then the next AC cycle turns it on again. If the signal is ABSENT, the device turns off at the first arriving zero crossing.
If a solid state switch is used with a DC circuit, it will turn on the first time it's triggered and STAY on, because there is no "0 voltage period" to allow it to turn off.
The only way to shut off the solid state relay used in a DC circuit would be to turn off all the power (making it sort of useless for DC use).
Opensourcerer:
So my switch arrived today and this circuit worked perfectly.. I just didn't have the arduino connected to it. But just triggered it with the DC+
For the trigger can I take the 5v from anywhere as long as the source has its own ground??
PS, the relay module wasn't recommend to me I just browsed google and thought I could use it for my project.
Grumpy_Mike:
Yes.
In fact you might not need a 5V at all. A lot of these relay modules work with negative logic. That means if you connect the relay control line to ground it will switch on, Otherwise you can connect the relay control to the 5V relay power line.
So my project is almost complete but i just don't have a powerful enough trigger. the device i'm using to trigger the switch is only 5v 55mA and all it did was flash the led on and off every time it connects. I tried using the earth from it but it done nothing.
is their any way of borrowing a small amount of power from the dc+ with a resistor or something so that when the trigger device connects it then has enough power to activate the switch.
or is their a smaller relay module that can be recommended that can activate the switch on a 5v 55mA feed??
the device i'm using to trigger the switch is only 5v 55mA
That is more than enough to trigger a relay module.
Have you wired up the power side of the relay module correctly like the diagram?
is their any way of borrowing a small amount of power from the dc+ with a resistor or something so that when the trigger device connects it then has enough power to activate the switch.
Just connect the relay control to the relay power. No need for any resistor.
I have copied this diagram exactly and like you said when i connect connect the relay control to the relay power t clicks, a green light comes on and my charger starts charging my phone. which is perfect..
Now i disconnect the relay control from the relay power. Now i T join the relay control to the 5v 55mA positive from a separate device.
Now when the separate device turns on it should activate the the relay and start charging my phone. but it only makes the green light flash then nothing.
if you say that is correct and is enough power to activate the relay then i will have to borrow the voltmeter from work again to measure the external device live feed and make sure its a constant active.
Where do you find these links?? I browsed for age's before asking on here!! My switch now works a treat. Thanks a lot for all your help. I learnt more then I thought I would!
I started with zero knowledge but was set out to make a switch.. I felt the relay module I chose was a simpler and safer place to start.
I just had a read from that link you sent me and it looks like I practically does the same as what I just put together plus it looks smaller and is silent.
If any What would my negatives be if I chose to use a transistor instead?
If any What would my negatives be if I chose to use a transistor instead?
A relay gives you total isolation from the circuit you are controlling. With a transistor you need to have a common ground. Also the transistor "robs" a small amount of voltage from what you switch, about 0.7V where as a relay is just a pure switch.
There are ways round this by using a FET and optical isolator but it is getting more complex.
Finally there is always a tiny bit of leakage current associated with solid state switching and not with a relay.
