More specifically, an incandescent bulb is a light-emitting PTC thermistor. The resistance of the filament is very low at room temperature, acting like a short circuit. With a lot of current, the filament heats up which causes the resistance to go up as well (PTC = positive temperature coefficient). As the resistance goes up, the current goes down, and the filament reaches an equilibrium temperature.
Incandescent light bulbs can be used as protection devices for repairing electronic equipment. If you make a mistake during the repairs and cause an accidental short circuit inside the device, the incandescent bulb (wired in series with the device) will limit the current based on the wattage of the bulb. 120 Watt bulb on 120 V AC circuit => 1 amp max current through the device. For a 60 W bulb the limit is 0.5 amp.
This is a lot lower current than the usual 15 amps allowed (before tripping the breaker) by a common NA household circuit.
We can expand on that a bit. A breaker does not simply open at its rated current. It should actually never open at the rated current. At 2x the current it takes some time. At 10x the rated current it still takes WAY too long. Traces, components, etc. everything are long vaporized at that point. And this makes sense too, they protect the wiring in the house, not devices with unknown power draw and current spikes.
Clarifying that the equipment should always be fixed disconnected from AC, the light bulb is supposed to assist in TESTING the fix, in case something in the equipment is still broken.
For those of you who would like to do stuff of this kind, here's a video of Jeff Geerling showing how to use a microcontroller board and a power supply to blow up a capacitor! (He also shows a few other things you can do with microcontroller boards.) https://www.youtube.com/watch?v=Sd42q3OaOrE
28 Comments
TropicalDingdong@lemmy.world · 51 pts · 243d
All electronics are light emitting resistors if you use them wrongly enough.
SpaceNoodle@lemmy.world · 20 pts · 243d
And smoke machines
Brickhead92@lemmy.world · 5 pts · 243d
Release the magic smoke!!
solomonschuler@lemmy.zip · 2 pts · 242d
four@lemmy.zip · 11 pts · 243d
Even when used correctly, they are above absolute zero, so they emit light. Just not in the spectrum visible to human eye
SmackemWittadic@lemmy.world · 5 pts · 243d
In that case do I count as a LER since living beings emit IR?
marcos@lemmy.world · 3 pts · 243d
Nah, plenty become open gas lamps before that.
5714@lemmy.dbzer0.com · 47 pts · 244d
We have gone full circle; LER is the new retronym for light bulb.
ulterno@programming.dev · 7 pts · 243d
Without the bulb around it.
vithigar@lemmy.ca · 45 pts · 243d
Incandescent lightbulbs are literally this.
chonglibloodsport@lemmy.world · 19 pts · 243d
More specifically, an incandescent bulb is a light-emitting PTC thermistor. The resistance of the filament is very low at room temperature, acting like a short circuit. With a lot of current, the filament heats up which causes the resistance to go up as well (PTC = positive temperature coefficient). As the resistance goes up, the current goes down, and the filament reaches an equilibrium temperature.
Incandescent light bulbs can be used as protection devices for repairing electronic equipment. If you make a mistake during the repairs and cause an accidental short circuit inside the device, the incandescent bulb (wired in series with the device) will limit the current based on the wattage of the bulb. 120 Watt bulb on 120 V AC circuit => 1 amp max current through the device. For a 60 W bulb the limit is 0.5 amp.
This is a lot lower current than the usual 15 amps allowed (before tripping the breaker) by a common NA household circuit.
Eheran@lemmy.world · 7 pts · 243d
We can expand on that a bit. A breaker does not simply open at its rated current. It should actually never open at the rated current. At 2x the current it takes some time. At 10x the rated current it still takes WAY too long. Traces, components, etc. everything are long vaporized at that point. And this makes sense too, they protect the wiring in the house, not devices with unknown power draw and current spikes.
trolololol@lemmy.world · 4 pts · 243d
Clarifying that the equipment should always be fixed disconnected from AC, the light bulb is supposed to assist in TESTING the fix, in case something in the equipment is still broken.
HugeNerd@lemmy.ca · 0 pts · 242d
Then it's not a thermistor, that's for sensing.
HeyThisIsntTheYMCA@lemmy.world · 2 pts · 243d
And those shitty hot plates
solomonschuler@lemmy.zip · 2 pts · 242d
vithigar@lemmy.ca · 2 pts · 242d
Fair point! Any electrical component that is not a superconductor is technically a resistor in addition to whatever else it does.
Lushed_Lungfish@lemmy.ca · 14 pts · 243d
Isn't this a light bulb?
officermike@lemmy.world · 13 pts · 243d
Been there, done that, never attempted CRT repair after that.
yucandu@lemmy.world · 9 pts · 243d
Yeah but did you know LEDs are also photodiodes? You can shine a light on them and read that as input voltage.
This guy has a great project where he turns his LEDs into a programming interface using his phone's flashlight:
https://www.youtube.com/watch?v=IHD3ji-F600
JohnSmith@sopuli.xyz · 7 pts · 243d
Once the smoke has cleared we check the connections we made earlier.
f4f4f4f4f4f4f4f4@sopuli.xyz · 7 pts · 242d
IphtashuFitz@lemmy.world · 7 pts · 243d
Thanks to the capacitor plague 20+ years ago I had to deal with a bunch of FEG’s (flame emitting GPUs)…
brognak@lemmy.dbzer0.com · 1 pts · 242d
Ugh, that picture triggered a lot of buried PTSD 😅
teft@piefed.social · 6 pts · 243d
Everything is a light emitting resistor if you push enough power through it.
solomonschuler@lemmy.zip · 1 pts · 242d
Eat_Your_Paisley@lemmy.world · 5 pts · 243d
Someone is going to celebrate new computer day pretty soon
MehBlah@lemmy.world · 4 pts · 242d
Don't let the smoke out. All electronics work due to having magical smoke inside. If you let the smoke out then it stops working.
Gork@sopuli.xyz · 3 pts · 243d
I once discharged a 5 F capacitor into a 1 Ohm resistor.
It created an unpleasant smell on burning up.
yetAnotherUser@lemmy.ca · 3 pts · 243d
For those of you who would like to do stuff of this kind, here's a video of Jeff Geerling showing how to use a microcontroller board and a power supply to blow up a capacitor! (He also shows a few other things you can do with microcontroller boards.) https://www.youtube.com/watch?v=Sd42q3OaOrE
ulterno@programming.dev · 2 pts · 243d
Seems kinda hard on the PCB though.
But would be useful when you also want to desolder nearby components at the same time, so multipurpose.