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This is mostly about capacitors, and explosions…maybe a little about marriage!
(It’s still about a projector!)
A capacitor is a device for storing electrical energy. They are interesting: very simple, very effective. Just one of quite a few things that modern society couldn’t exist without, but few people even know exist.
Basically it’s that whole thing about opposites attracting, except maybe not as much about dating choices in this particular case. If you have two electrically charged plates (+ and -) and you start bringing them closer and closer together, you build up an electric field and store energy. If you stuck a wire between them, you’d get a spark and electric charges would flow between the two plates until the energy was released.
This is what capacitors do: put a voltage on plates across some insulator and store energy, the higher the voltage, the closer together, the more energy in the same area. The problem is the higher the voltage, the closer together the more likely you are to get that spark even without the wire, so that insulator needs to be very good!
These are really useful. For example, we have Alternating Current all over the world. This is where the voltage swings positive and negative 50 or 60 times a second. Any analog or digital signal processing system needs to be powered by DC voltage: constant like a battery, electrically quiet so they can handle their own signals without any argument from the power lines. Where do you think society would be if whenever we wanted to watch TV or do our homework we needed to round up a whole bunch of D-Cells?
What can we do about this? We can put the AC through a rectifier: basically fold it in half so all the bumps, both positive and negative, now point positive. This is a step in the right direction, but the voltage is still bumpy! Let’s stick some capacitors in there, so when the voltage bumps are rising they’ll store energy and when they fall, they’ll release it and fill in those voltage valleys: smooth them out. Somewhere close to you, and everywhere around the world this is happening all the time.
This is also why when people here complain about excessive hum, the discussion often turns to capacitors.
They do other useful things, like for example they allow more current to pass as the frequency of a signal rises, so they can be used to block DC and let AC pass. Commercial radio and TV would never have existed without the variable ones in tuners. There are hopes someday to use really immense capacitors to store solar-electric energy: they are more efficient than a battery. (Batteries have nothing to worry about for a long time...)
So, we want more voltage, closer together for more energy storage in a smaller space. It turns out that Aluminum Oxide is a wonderful insulator, even when very thin. If you have an aluminum electrode in a can of conductive electrolyte goo, through the miracle of Chemistry (…I’ve always been more of a Physics guy!), you can cause a thin layer of aluminum oxide to form on the electrode by putting a positive voltage on it.
-Look what we have now: conductive plate, extremely thin insulator, conductive goo. We have now “invented” a capacitor, an Electrolytic capacitor to be exact! (We’re a little late to the party…)
Many of the largest capacitors in the world are electrolytics. They store a lot more energy in a given space than other technologies, but there are drawbacks. Here are some of them:
Do you sense a theme here? Every electrolytic cap, everywhere is a tiny, potential bomb: a stink bomb, no less!
Meanwhile, back at the Cinema:
I had a “new”, yet ancient machine just stuffed full of old electrolytic capacitors. An old employer of mine never sold anything with caps stored more than 5 years, and we were way, way over this limit. My original plan included the possibility of yanking them all out, buying new ones and soldering them in. Once I figured out how many there were, I REALLY didn’t want to do that!
Spock would say “There are always possibilities”. As a matter of fact, in Star Trek IV he used photons stolen from a Navy ship to regenerate depleted dilithium crystals and bring the Whales to the 23rd century. (I can’t wait for the Musical to come out!)
I wanted that! Regeneration! (-but without stealing anything from the Navy…)
It turns out it really is possible if the electrolytic fluid hasn’t dried up. Electrolytics are originally formed-up by gradually applying voltage. I was going to do the same and hope it would work a second time. (Why not? I had nothing to lose.)
Now, obviously, this was no time to go in full throttle: 115V at the wall was just begging for scenario #3! We needed to take a leisurely cruise around the block, make sure the brakes and steering were OK before we stomped on the gas.
I brought out a model train power pack. The accessory terminals supplied 16VAC. This is a little more than 10% of 115VAC: it seemed cautious enough for a start. I applied it to the power prongs on the cord (clip leads) and turned on the power. I turned on the sound and got a faint hum, almost inaudible. I figured I wanted to slowly tease a layer of oxide to form on those caps. I also figured at such a low voltage nothing was going to happen very quickly, so I left it on all weekend.
After that, I decided I wanted to step up my game: I got out another power pack and jumpered it in series. I measured the combined voltage at 32VAC to make sure the phasing was correct (have to get all your bumps going in the same direction or they’ll cancel out and you’ll get a big Zero!).
I connected up (more clip leads). I got more hum than before. I put the machine in “Forward” and nothing moved, but then I flicked the shutter and it kept moving! Slowly it built up speed: nothing more than a few FPS, but it was moving! To me this was a little like that moment in Science Fiction when somebody comes out of centuries of suspended animation, looks up at the doctors and says “…where….am I?”. For the first time I saw this projector actually DO something!
I figured I was getting a head start cleaning the crud off that commutator: I let it run for a while.
I also let those all those capacitors spend a couple of days with 32VAC input: build up some oxides at a non-threatening voltage. I hadn’t popped a fuse or smelled that awful burst electrolytic smell (-like a thousand pounds of dead fish in the hot sun!), so I was encouraged.
It seemed like a good time for an intermediate step: 50VAC, maybe 75VAC, but I was out of power packs! Maybe I could bring it to work: plug it into a Variac. The problem is bringing something that might burst into smoke into a building with very sensitive smoke detectors and an on-site fire department seemed…unwise! I’d already met the F.D. twice under situations with a lot less embarrassing explanations and this didn’t seem a smart career move. (Next time, maybe they'll let me ride in the fire truck!)
Despite all that, I felt BOLD: it was time to go for 115 Volts!
(It’s still about a projector!)
A capacitor is a device for storing electrical energy. They are interesting: very simple, very effective. Just one of quite a few things that modern society couldn’t exist without, but few people even know exist.
Basically it’s that whole thing about opposites attracting, except maybe not as much about dating choices in this particular case. If you have two electrically charged plates (+ and -) and you start bringing them closer and closer together, you build up an electric field and store energy. If you stuck a wire between them, you’d get a spark and electric charges would flow between the two plates until the energy was released.
This is what capacitors do: put a voltage on plates across some insulator and store energy, the higher the voltage, the closer together, the more energy in the same area. The problem is the higher the voltage, the closer together the more likely you are to get that spark even without the wire, so that insulator needs to be very good!
These are really useful. For example, we have Alternating Current all over the world. This is where the voltage swings positive and negative 50 or 60 times a second. Any analog or digital signal processing system needs to be powered by DC voltage: constant like a battery, electrically quiet so they can handle their own signals without any argument from the power lines. Where do you think society would be if whenever we wanted to watch TV or do our homework we needed to round up a whole bunch of D-Cells?
What can we do about this? We can put the AC through a rectifier: basically fold it in half so all the bumps, both positive and negative, now point positive. This is a step in the right direction, but the voltage is still bumpy! Let’s stick some capacitors in there, so when the voltage bumps are rising they’ll store energy and when they fall, they’ll release it and fill in those voltage valleys: smooth them out. Somewhere close to you, and everywhere around the world this is happening all the time.
This is also why when people here complain about excessive hum, the discussion often turns to capacitors.
They do other useful things, like for example they allow more current to pass as the frequency of a signal rises, so they can be used to block DC and let AC pass. Commercial radio and TV would never have existed without the variable ones in tuners. There are hopes someday to use really immense capacitors to store solar-electric energy: they are more efficient than a battery. (Batteries have nothing to worry about for a long time...)
So, we want more voltage, closer together for more energy storage in a smaller space. It turns out that Aluminum Oxide is a wonderful insulator, even when very thin. If you have an aluminum electrode in a can of conductive electrolyte goo, through the miracle of Chemistry (…I’ve always been more of a Physics guy!), you can cause a thin layer of aluminum oxide to form on the electrode by putting a positive voltage on it.
-Look what we have now: conductive plate, extremely thin insulator, conductive goo. We have now “invented” a capacitor, an Electrolytic capacitor to be exact! (We’re a little late to the party…)
Many of the largest capacitors in the world are electrolytics. They store a lot more energy in a given space than other technologies, but there are drawbacks. Here are some of them:
- If you connect them backwards, the oxide layer breaches, a lot of current flows, the electrolyte gets hot, boils, and the pressure may explode the can. (-Been there!)
- They are only for DC, if you connect them across unrectified AC, the oxide layer breaches, a lot of current flows, the electrolyte gets hot, boils, and the pressure may explode the can.
- They need to have voltage on them to maintain the oxide layer. They don’t do well in long term storage for this reason. The oxide layer gradually dissipates. If the oxide layer disappears, when voltage is applied, a lot of current flows, the electrolyte gets hot, boils, and the pressure may explode the can.
Do you sense a theme here? Every electrolytic cap, everywhere is a tiny, potential bomb: a stink bomb, no less!
Meanwhile, back at the Cinema:
I had a “new”, yet ancient machine just stuffed full of old electrolytic capacitors. An old employer of mine never sold anything with caps stored more than 5 years, and we were way, way over this limit. My original plan included the possibility of yanking them all out, buying new ones and soldering them in. Once I figured out how many there were, I REALLY didn’t want to do that!
Spock would say “There are always possibilities”. As a matter of fact, in Star Trek IV he used photons stolen from a Navy ship to regenerate depleted dilithium crystals and bring the Whales to the 23rd century. (I can’t wait for the Musical to come out!)
I wanted that! Regeneration! (-but without stealing anything from the Navy…)
It turns out it really is possible if the electrolytic fluid hasn’t dried up. Electrolytics are originally formed-up by gradually applying voltage. I was going to do the same and hope it would work a second time. (Why not? I had nothing to lose.)
Now, obviously, this was no time to go in full throttle: 115V at the wall was just begging for scenario #3! We needed to take a leisurely cruise around the block, make sure the brakes and steering were OK before we stomped on the gas.
I brought out a model train power pack. The accessory terminals supplied 16VAC. This is a little more than 10% of 115VAC: it seemed cautious enough for a start. I applied it to the power prongs on the cord (clip leads) and turned on the power. I turned on the sound and got a faint hum, almost inaudible. I figured I wanted to slowly tease a layer of oxide to form on those caps. I also figured at such a low voltage nothing was going to happen very quickly, so I left it on all weekend.
After that, I decided I wanted to step up my game: I got out another power pack and jumpered it in series. I measured the combined voltage at 32VAC to make sure the phasing was correct (have to get all your bumps going in the same direction or they’ll cancel out and you’ll get a big Zero!).
I connected up (more clip leads). I got more hum than before. I put the machine in “Forward” and nothing moved, but then I flicked the shutter and it kept moving! Slowly it built up speed: nothing more than a few FPS, but it was moving! To me this was a little like that moment in Science Fiction when somebody comes out of centuries of suspended animation, looks up at the doctors and says “…where….am I?”. For the first time I saw this projector actually DO something!
I figured I was getting a head start cleaning the crud off that commutator: I let it run for a while.
I also let those all those capacitors spend a couple of days with 32VAC input: build up some oxides at a non-threatening voltage. I hadn’t popped a fuse or smelled that awful burst electrolytic smell (-like a thousand pounds of dead fish in the hot sun!), so I was encouraged.
It seemed like a good time for an intermediate step: 50VAC, maybe 75VAC, but I was out of power packs! Maybe I could bring it to work: plug it into a Variac. The problem is bringing something that might burst into smoke into a building with very sensitive smoke detectors and an on-site fire department seemed…unwise! I’d already met the F.D. twice under situations with a lot less embarrassing explanations and this didn’t seem a smart career move. (Next time, maybe they'll let me ride in the fire truck!)
Despite all that, I felt BOLD: it was time to go for 115 Volts!
Currently having a presumably faulty vcr (it does play, but with distorted color) sitting idle in my storage. Since it's Panasonic HS-100, quite a high-end ones which is too decent to throw it away, I should give it a chance at least.
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