It has been many years since my electronics days, but I believe a diode does have a fixed voltage drop. I think it's around .7 volts if I remember correctly. So it does regulate the voltage in some respects.
Anthony Watson
HerHusband presented the following explanation :
Yes, that is a forward voltage drop across the junction. The voltage depends on the materials used in the device. The regulation function of a diode is usually a reverse voltage taking advantage of the breakdown characteristic. IOW a reversed diode as a shunting device. The same can be used as a reference diode to control a transistor regulator. Zener diodes come to mind for this.
I had an ISP thast must have been plagued with a similar problem (or, a software bug) as I noticed that if I was pulling down an ISO at certain times of the overnight that the connection would "reset".
I knew it wasn't anything on my end (as I'd be sitting there, at the time -- doubtful they had staff on site at all hours of the night!)
I've been trying to replace all of our clocks with designs of my own (I like clocks!). Part of the design process is to include "time services" so they automatically track a common reference (that *they* elect, if the previous "reference" is unavailable).
A "regular" silicon diode has *about* a 0.7V forward drop. Though the actual drop is dependant on the current flowing through the junction (as current increases, the drop increases -- but only slightly; not proportionately as with a purely resistive device). There's a "knee" in the V-I curve at that point (but, all knees are "rounded" to some extent!)
LED's, OTOH, have a much higher forward drop. Some of the high efficiency ones are as LOW at ~1.7-1.9V. Most, however, tend to be higher -- ~2.1 for Red/Yellow/Orange and closer to 3.4 for the Blue/White devices.
(Even these are just ballpark numbers as it depends on the dopants used)
Germanium ("Is there life on Germanium?") diodes have forward drops in the 0.2V range. Schottky diodes are in the 0.15-0.45V range.
And, of course, you can get zeners at all sorts of voltage ranges (but, these are operating in reverse bias when zenering)
I suspect most folks can find their way around their own home in TOTAL darkness. If you can't, hope you never wake to a house full of smoke!
Unless it's a new moon, there's usually enough light streaming in through windows and skylights, here, to see -- once your eyes become acclimated to the darkness.
Ditto. Wallet goes on the dresser, keyfob gets hung on a hook by the entrance to the garage.
I watched construction in a new neighborhood a few years ago. They put all utilities underground.
That'd be nice here, but this area is older.
I lost natural gas once, because of a defective regulator that had to be replaced. They had to purge the line at my water heater. I was there and was surprised at how loud a noise the gas made when it came through.
[snip]The last time I used a flashlight was to see how much gas was in a little generator (a Honda EU2000i). At the time it was very sunny outside, but I needed light INSIDE the tank.
On the keyring with the lost keys.
Generally, I don't turn off the light unless I turned it on and no one has entered since. However, the problem DOES happen.
I live in one of the few areas around here that don't have deregulation. One difference is rates are much lower (I pay about half what people in a nearby city pay).
BTW, when figuring rates, I skip all the misleading stuff and just divide total bill by usage.
Mostly like that here, but last year we had a 4-day outage.
At home, I try to keep a flashlight in a known location (2 flashlights are better, in case one doesn't work). It's also easy to find since it's next to the cable phone adapter (with battery and it's on a UPS).
I have an old UPS that won't put out much current, so it's no good for a PC. However, it DOES work with a string of LED holiday lights, so it's an emergency light as well as a hall light ("lilly's lights" named after a small cat that slept in the hall).
A very simple definition that is sort of correct but leaves out a lot of stuff.
A diode has a threshold voltage. It the supplied voltage is less than that, there will be no current. Otherwise the diode will conduct. It will conduct as much as needed to limit the voltage across it to the threshold. This means a diode may conduct excessive current if nothing is done to limit it. This is frequently a resistor in series.
An important thing about a diode is that the threshold is different for each polarity. That simple definition is correct when the voltage is between one threshold and the other.
When the diode is in series, it will have a voltage drop equal to the threshold voltage (which threshold depends on polarity).
BTW, I know that semiconductor junctions are even more complex than that.
And reset all those "power amnesiacs", equipment that can't remember it's supposed to be ON.
I have a LED light, that can be set to one of 7 colors. I prefer green (which looks brightest), but when power is first applied it always comes on white. However, in this case I find that useful. It's a power outage indicator.
Not AC with battery backup. I find that those with battery backup are usually slow on it, and so worse than no battery (wrong time not obvious failure).
I think, overall, it is cheaper. Higher up-front costs but lower maintenance costs.
It's a mmixed bag, here. Some parts of town are crisscrossed (literally) with hanging cables (at various heights and traveling in different directions). Other areas are more "pristine".
We had a city-wide outage a few winters back. Too much demand for the supply. I.e., you had gas -- but not enough flow to keep appliances from shutting themselves down (safety). They eventually cut the gas supply to certain parts of town so the rest of the town could have gas at a usable pressure.
Just tell him/her to leave it ON so when the keys get misplaced, they'll "light the way" to their retrieval!
I told the guy out in the gym that he should not have turned off the light particularly when someone was still in there. He did not realize he did it and it was his natural reaction to turn off the light. I was beyond the set of lockers where the switch was so there was no one in the room that he turned the light off in.
That little light died but a friend gave me a light that he had given to employees and customers when he retired. Great on the key chain and lots of light but batteries went and it would have cost me over $10 to replace the lithium batteries. I prefer lights with AAA or AA batteries.
I hear about the Simply Safe home alarm system which you install yourself and is cheap with no wiring. You can bet cost of battery replacement is a big negative.
The (forward) voltage drop depends on the semiconductor material. .7V for silicon diodes, around 2V for LEDs.
Reverse voltage drop can vary greatly according to design. I've see about 3V (for a LED) to 1KV (1N4007 IIRC).
With either polarity, voltage exceeding that will cause current to flow. This is called "breakdown" and is not harmful unless the diode's maximum current is exceeded. A LED is normally operated in forward breakdown (necessary for it to light).
A diode is a voltage regulator. If you connect a LED (and nothing else) to a car battery, the LED will try to bring the battery down to 2V, and try to handle nearly infinite current. I did this once and didn't even see any light before there was a POP and half the LED disappeared. You need a resistor that drops the excess voltage (10V here) without exceeding the LED current (typically 30mA).
I nominate this for the post of the month. Do I have a second?
1) some fellows have little common sense 2) Dollar Tree and Harbor Freight some times have lithium coin cells. Might not been ten bucks in batteries. 3) Don't know about the Simpli Safe. But, most likely you are right.
If it's not too cloudy. Anyway, I try to take a flashlight while going for a walk at night.
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