Whats the best way to use multiple LDRs to power up an LED? Currently I’m using one LDR which turns on an LED when it senses light. But now I want to use three LDRs (at different locations) to trigger the same LED. The LED should turn on when any of the three LDRs sense light.  Thanks in advance!
124220
I wnat to use 8 IR sensors (4 on front of vest, 2 on back and 2 on headband like lazertag vest) that when each of sensors hitted by IR, turn on a led. I don't want to use any microcontroller so a simple circuit is what I want. I can achieve this by one IR reciever but I want to use 8 sensor. Help me please.
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How can I have a LED either on or off (not in between) depending on night or day with basic electronics? I have created the circuit below, but it only shines and in darkness it dims.    The photo-resistor is about 3kΩ when light shines and about 1MΩ when dark.  I want my LED to shine at night and be off at day.  What is the simplest way I can achieve this?
117960
I've been looking to install LED strips, either RGB or white for lighting and ambiance. It wouldn't be the main lighting of the room, so no necessity for high power LEDs.  The perimeter of the room is a little less than 25 meters. Looking around in online stores, I saw that the reels come in maximum lengths of 5 meters, so I would need five of those.  What I'm not sure is how to connect the strips together.  I was looking at , or  with .  If I choose the white LEDs, what power supply, controller, and connector would you recommend to be able to daisy chain the strips?  If I choose the RGB LEDs, what kind of data repeaters would work to be able to control all the strips at once?
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I'm working on a guitar, and the plan is to use three latching push buttons so that each pickup can be turned on and off individually. I'm fairly confident that the following diagram should work for that (Feel free to correct me)   The buttons I want to use are , which have a built-in LED when turns on when the button is pressed.   Which brings me to my question: Is there a way to power the LED? If I introduce a 9volt into the wiring, wouldn't that cause problems with the guitar's standard electronics?
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How would I go a about making volume light beams?  I have have tried  various tutorials, but they must be for a older version. as applying them does seemingly nothing.  A link to a functioning tutorial would be greatly appreciated as well.  I don't have a picture or .blend to show, as my problem with atmospheric lighting does not pertain to any specific scene.
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This past week at Menards I bought 2 Smart Electrician® 3650 Lumens 46" LED Linkable Shop Light Model Number: 0053-0011  |  Menards® SKU: 3481400.  The LED shop light fixture has a glow to it. Looked like the LEDs were turned on, but not all the way. The power switch is turned off. Don’t know why I did this but I took one of those three prong adaptors converters to two prong and to my surprise the light fixture didn’t light up. I unplug the cord with the adaptor and turned it around and it still didn’t light up. The power supply electronics inside the light fixture must be using the earth ground wire somehow. Using my volt meter. I measured to earth ground to the green wire that comes out of the adaptor and to my surprise depending how I plug in the adaptor. I’m getting 112 volts AC. That's because the adaptor isn't keyed and I'm switching the HOT and NEUTRAL around depending how I  plug it in.  I connected the LED light fixture to “Safety Analyzer tester”. When I press the “Open Ground” button, the fixture stops glowing (lightly lite LED’s).  Looks like the power supply circuit inside the fixture has a connection to “Earth Ground”.  I then switched the “Normal” on the polarity switch to “Reverse” and the LED’s were off. Switching the Neutral to open position has no effect. I'm thinking of taking them apart and see inside what's going on or take them back.  I figured out the problem.    In this light fixture you can clearly see the white wire (neutral/common) is connected to the light switch, turning the power off the LED light strip. Commonly we switch off the “HOT” to your light socket so when you change your bulb you have a less of a chance of getting electrocuted (that’s another story for later). Sometimes in Power supply circuits they place capacitors in there to help filter electrical noise out. Also known as suppressers (electronics to reduce unwanted noise or oscillation in a circuit or unwanted frequencies in a signal). Depending on how or where they are placed in the circuit it could possible cause some issue if not installed correctly or if the circuit isn’t designed correctly.   Since the BLACK live wire is connected to the LED PCB all the time, anything connected to that line will potentially be LIVE voltage, that way when I disconnected the earth ground from the socket and measured 112 volts on it. My guess is they have capacitors connected to both LIVE and NEUTRAL to the earth ground wire.  The current is flowing through capacitor C2, just enough to turn the LED’s on slightly. If the switch was on the hot side, this problem wouldn’t be happening. I still may use them just not connect the “earth ground” wire. Because that’s providing the return path for lighting the LED’s.
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How do I share a single crystal (not a complete oscillator module) between two micros? Is it OK to just connect everything as normal for the first micro and also directly connect its XO to the XI of the second microcontroller? I expect to place the micros very close together on the board.
105516
I'm looking at a diagram and wondering if I could use just one resistor to limit the current of the LEDs instead of multiple resistors so that the cathodes are all connected to the same resistor.    JL
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Can somebody explain in simple words. real life example light help and limitations of these schemes etc.
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As many of you probably know, a normal light emitting diode, while very handy as a cheap and ubiquitous indicator, can double as a power generator. The mechanism is the same that is exploited in photovoltaic cells, aka solar panels.  When an LED is exposed to light it produces a current flowing from anode to cathode. This current can be used to directly power a device, or to charge a capacitor so that a periodic load can use the stored charge all at once, when needed.  To give you a better idea of the values involved, the short circuit current ranges from tens of nanoamps up to a few microamps, while the open circuit voltage is somewhat less than the standard forward voltage of the LED.  I am currently in the process of choosing a range of LEDs to test them and see if they are suitable for my application, but I am kinda stuck, mainly because using a led to power something is convenient only money wise, while a photovoltaic cell or even a photodiode is a better choice under many other aspects. No manufacturer that I have seen list the photogeneration current in the datasheet, and this seems fair enough to me, but since I want to avoid testing thousand of LEDs I would like to buy a selected range of them, so I need to better understand the underlying mechanism that leads to photogeneration.  Let's just write down the diode equation: $$ I_D = I_s(e^{\frac{V_D}{V_t} - 1})-I_G $$         &ndash; Schematic created using   Where \$I_s=J_s\cdot A\$ is technology dependent, and die area dependent. \$I_G\$ is the generation current, and is the parameter I am interested in maximizing.  Here are some things I have thought of:  LED color since the LED can absorb a lightbeam only if the energy it carries is greater than the gap, choosing LED with low energy (i.e. low frequency) gap is a must, to be able to absorb a wider portion of the spectrum. This lead me to choose red or infrared LEDs.  max current max forward current is proportional to die area, and power dissipation capabilities. Since photogenerated current is proportional to area, choosing an high current LED seem wise to me.  forward voltage this is somewhat related to the open circuit voltage and is not currently an issue for me, and I believe it has no relationship with photogenerated current.  reverse current I am not sure this has much to do with photogenerated current, but the bigger the reverse current, the bigger the area, which is a good thing.  breakdown voltage I do not think this has a relationship with photogeneration.  My question finally is: Do you agree with my analysis, and do you think I am missing something? or better What are the parameters to look at when searching for a photovoltaic panel in the LED section of a supplier?
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I have an adjustable 24VDC power supply.  I have 1W LEDs that I was planning on stringing 7 or 8 in series to get approximately 24V across all of them together. They are rated 3.3-3.8V each. Do I need a resistor in series to maintain current? I was thinking so since a lit LED is basically a short? I can't find an answer to what it is really needed for, just that most people say to put a resistor in series to 'limit current'...  if so, it would be a small resistor, around 2 or 3 ohm?
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So I'm wondering if anyone has any information about the Dell power supplies which have 3 contacts on the barrel.    I know the 3 are power, ground, and some sort of communication link. Does anyone know what the communication line is for and/or what kind of protocol it uses?  Thanks  EDIT The reason I ask is I'm considering trying to build my own semi-advanced charger (not for a laptop but something else... it's a long story) and while I'm sure I could figure out a charging circuit given the internet as a resource, I was wondering what they use the communication line for and if it's necessary for my purposes. It seems the answer is no since I will be the only one using my device and thus don't need to worry about people plugging in not kosher chargers...
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I have a question that may seem silly, but I am only new at this type of thing:    Is there a sensor that I could connect to an LED (via an integrated circuit of some description, I assume) that would allow the LED to light up when the sensor came into range of a certain frequency?  I would like to run this setup from a 9v battery, if possible.  If this is possible, could I get a parts listing for what I would need for this setup?  Added:  What i was trying to achieve was a small device that incorporated an led that lit up when it detected a certain frequency/radio wave from another device (possibly a vehicle). Maybe an antenna instead of a sensor might be the go? Not sure yet and I am still very green with this. It was just an idea I had that may be useful for my work environment.
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I am trying to develop a very high reliability product, with a MTBF exceeding 100,000 hours, hopefully in the 250,000 hours range. Yep, I know - stupidly high reliability, at least 10 years.   Most LED's I've seen have a reliability rating of only 20,000 hours. What happens after this? Do they reduce in output too much? Are they usable as power indicators past this point?
95548
I have a couple of outdoor light sockets with built in motion detectors. These seem to work as you'd expect with regular incandescent bulbs- you can set a timer for how long you want them to be on when motion is detected and they light up fine.  When replacing them with LED bulbs however they blink rapidly instead of staying on. I'm not talking about a 50hz buzz or whatever, they completely power off and on rapidly, almost like they are trying to strobe. The blinking is erratic, it will go for 10 seconds then go dark completely, then blink again for varying amounts of time. I see this same behavior with LED bulbs in both of the sockets, which are the same brand and model of motion detector outdoor light sockets.   The bulbs are Verbatim A19 6-Pack Warm White 3000K LED Bulb, Replaces 60W, Non-Dimmable 99072 if that matters.   I want to replace everything in the house with LED, but not sure how to make these two sockets work correctly. Suggestions?
839
I have 10 Canon 5DmkII cameras which I want to fire simultaneously... How can I accomplish this task repeatedly and reliably?  NOTE: Although I mention 10 cameras, it will be a 'super bonus' if the solution is scalable to n cameras...
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Note: I am very new to the more advanced side of electricity. I do not have a firm grasp on the exact mechanics.  Lets say I have an example circuit:  5V Power Supply -&gt; LED -&gt; Resistor -&gt; Ground  Now the LED is receiving 20ma and 5V. If I were to switch the LED and the resistor however, the LED should receive less voltage but the same current, so wouldn't it be dimmer? Or would it receive the same voltage?  I've looked at these two threads and their answer doesn't help.