I have a device that has an incandescent lightbulb (GE47 bayonet bulb) on 110 AC power.
When the bulb lights up, I want the arduino to react.
Options:
I could use a light sensor but am concerned if the bulb is burned out I would not be notified.
Somehow interface with the power to determine if power is turned on to the bulb. I am comfortable working with AC and have working with SSRs before to turn on power, just never tried to sense if it is turned on.
What is the best approach for determining this on state?
When the bulb lights up, I want the arduino to react.
Options:
I could use a light sensor but am concerned if the bulb is burned out I would not be notified.
What??? A light sensor (or your eye) is the best way to know if the light is working or not, regardless of the cause.
have working with SSRs before to turn on power, just never tried to sense if it is turned on.
You can get a regular relay with a 120VAC coil. That's the most foolproof way to do it.
Or you can get a SSR with 120VAC input. If you use a SSR make sure to check the output-side specs. A SSR designed to switch AC won't work with DC and sometimes a 120VAC or 240VAC SSR won't switch low-voltage AC.
You can also use a regular opto-isolator, but because of the voltage-drop across the input-resistor (almost the full line-voltage) you need a ~2W resistor and it will generate some heat (Power = Voltage x Current). (Approximately the same amount of power/heat has to be dissipated by a solid state relay that's controlled by 120VAC.)
You can use a current transformer (CT) to sense the current flowing through a single lead of an AC line. That will tell you if the bulb is on and working.
Learn how to use them here: CT sensors - An Introduction — OpenEnergyMonitor 0.0.1 documentation
Low voltage non-intrusive transistor circuit here that looks for "live" feed regardless if bulb working or not.
I have a device that has an incandescent lightbulb (GE47 bayonet bulb) on 110 AC power.
Uh, no you don’t. A #47 lamp is a 6.3 volt device. Apply 120 volts and it will... become a fuse. Is this an older piece of equipment with vacuum tubes? 6.3 volts is the standard voltage for the filaments in old tube equipment so #47 lamps were the most common pilot lights of the tube era.
If you want a failsafe system, that is you want to know if the lamp is working or defective, you need to sense both voltage and current. If you use a dc power source for the lamp, it will be much easier to detect if it is operating.
Some #47 trivia: In 1938, Bill Hewlett of Hewlett-Packard fame used one as a temperature dependent resistor in the original HP200 audio oscillator.
A cheap phototransistor in the back end of a short tube will do it it's pointed at the light. The tube blocks stray light from making false triggers. The PT uses light as the transistor control, it opens in light. Connected to a pin moded INPUT_PULLUP on one side and ground on the other you have a light switch, no resistors needed.
The sensor is there to detect if the bulb works. If it burns out, the sensor tells it so! The view of the sensor can be made very small if external light is a concern. Measure the current going to the bulb too and maybe use a 1-wire temperature sensor as a third way. If the bulb gets covered in dirt, the current and temperature sensors won't know that. If the detector gets covered in dirt, it will need attention so an error signal is not out of place.
Traffic lights had light sensors checking operating status of bulbs since long ago, those systems were multiply redundant except for the pre-led traffic light bulbs since there was only room for one set. I'm sure that redundancy has only gone up but then they had 3 chips running the same program and at every conclusion if two agreed and one didn't, it was cut as unreliable and repair service signaled.
corbinwinter:
When the bulb lights up, I want the arduino to react.
Options:
I could use a light sensor but am concerned if the bulb is burned out I would not be notified.
Seems to me the OP wants both.....
I'm confused what current is there to measure if the lightbulb doesnt work or that it's simply off? If you're talking about a regular incandescent light bulb on a table lamp. If the bulb burns out there's nothing to measure.
Light sensor is a good way to know if a light is on.
Now if you want to know if the light is on by other methods you could do a current sensor. They make different sizes (amp rating) get one that will handle your needs.
And when the bulb is working and on you can measure current flow.
But how... how possibly could that be used to know when the bulb is off? (sad face)
My only guess is that this is a bigger project. If it's an indicator lamp on a bigger project. YES! you can sense the difference between an ON (working) bulb vs an OFF (blown) bulb as long as current is flowing through the bigger system.
If this is a stand alone bulb no way to tell.
Either way current sensor is your best bet. A filament bulb should die open.
From the OP's inconclusive description, it sounds like he wants to know, or wants the arduino to know, when whatever drives the lamp was turned on, not if the bulb it self is working or not.... His pic only shows a lone lamp, not what it might be attached to. Being as how he thinks that he can apply 110 Vac to a GE#47 and not have it go POP, I tend to doubt that he really has any idea of what he really wants to do. it should be fairly simple to figure out a detection method, if we had all the pertinent information.
I really think that mulling over re-hashes of how to see if a bulb is burned out or not is a waste of time. Just my take on it.
