They run off of transformer power, and they have a mechanical switch on the case.
I want to be able to switch them on/off via an Arduino, but I also want to keep the original switch usable without having the Arduino attatched. (so, if the switch is on, OR the pin is on, then light the lamps.)
I also want to keep them as intact as possible, so replacing the LED bulbs or rewiring the signs themselves isn't an option.
Just some additional information:
I am currently thinking about placing a transistor in paralell with the primary switch, because this should give what I'm looking for.
If anybody has suggestions/improvements for this, they would be appreciated.
EDIT: I just thought of another idea:
If I hooked into the battery compartment, then I could use the arduino itself as a power supply and get rid of the transformer I am currently using to power it
If anybody has suggestions/better ideas for this (or reasons this wouldn't work), please let me know!
A MOSFET (which is a type if transistor) is the way to go.
There is a set of circuit diagrams available from one of the members here that shows how to do it along with loads of other stuff, but I can't remeber where. I'll have a look for it.
@Mark (or anybody else), a MOSFET would work well if I wanted to go for the parallel transistor-switch option, but does anybody know if the mock-battery option would work. (from what I've seen, I think an Arduino pin could control it with a 68-ohm resistor, but I'm not sure about that in the slightest).
thepenguin:
Just some additional information:
I am currently thinking about placing a transistor in paralell with the primary switch, because this should give what I'm looking for.
If anybody has suggestions/improvements for this, they would be appreciated.
EDIT: I just thought of another idea:
If I hooked into the battery compartment, then I could use the arduino itself as a power supply and get rid of the transformer I am currently using to power it
If anybody has suggestions/better ideas for this (or reasons this wouldn't work), please let me know!
Why the complication of a transistor in //el with the switch?
Just wire the arduino output to the input side of the switch through a diode. When the switch is ON and either the power is from the arduino, a battery or a wall wart it will work. If the switch is OFF it won't work, whichever power source you are using.
An Ardino pin can only source/sink a small amount of current (40mA) so you provide the current from a second source and control it with the transistor.
holmes4:
An Ardino pin can only source/sink a small amount of current (40mA) so you provide the current from a second source and control it with the transistor.
Mark
Current demand on these things is reportedly only 30mA, so that shouldn't be a problem.