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12 votes

Is my IC broken?

Has my IC been fried by the reversed battery Most likely, yes, because as you said: it was working before the motor disconnected and my dad put the battery in backwards In general, ICs are very ...
SamGibson's user avatar
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10 votes

Understanding basic photoresistor circuit

The HW5P-1 is in fact a phototransistor. This is the diagram of the example circuit from the datasheet: The circuit symbol is clearly a phototransistor, regardless of what the poorly translated ...
JRE's user avatar
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8 votes
Accepted

How to prevent photoresistor sensor from draining battery

Sleep on the watchdog timer (or other low power timer) instead and then only power the photodetector at the end of each sleep. Connect the top of the photoresistor circuit to a GPIO so that you can ...
Jasen  Слава Україні's user avatar
7 votes
Accepted

How fast is a photoresistor?

How small can the obstruction be? (I guess it depends on the surface area of the LDR, itself.) Yes, LDR tend to collect light from a larger area than photodiodes or phototransistors. A photodiode or ...
glen_geek's user avatar
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6 votes
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Why do LDR photocells use CdS and CdSe?

What makes cadmium selenide and cadmium sulfide such appealing semiconductors to make photocells out of? Cadmium sulfide and Cadmium selenide turn conductive in the visible wavelengths, they do ...
Voltage Spike's user avatar
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6 votes

How fast is a photoresistor?

The downside of LDRs is that they typically have a relatively large resistance and also a much larger effective area than photodiodes, making them lazy. If you read the voltage at a simple voltage ...
Sim Son's user avatar
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5 votes
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Confusing dark sensor circuit diagram

This is a crappy circuit. Run away. It seems the intent is that when there is lots of light, LDR1 goes down in resistance, which turns on Q1, which turns off Q2. When it's dark, Q1 doesn't turn on ...
Olin Lathrop's user avatar
5 votes

Understanding basic photoresistor circuit

The datasheet of this device isn't terribly clear. At some points it claims to be a drop-in replacement for a CdS sensor (i.e. a resistor whose resistance varies with light intensity) and at other ...
nanofarad's user avatar
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5 votes

How fast is a photoresistor?

As an addition to the other answers, typical CdS photoresistors have their maximum sensitivy at green light and nearly none for red and infrared. Also, their sensitive area is very uneven because of ...
Janka's user avatar
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5 votes

Accuracy of manufactured photocells (LDR) with respect to light intensity

Why is this information never(?) provided? Photoresistors are usually low cost binary sensors used to determine if it is light or dark in the environment. If you want to know the difference between ...
user1850479's user avatar
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4 votes

Best way to amplify the photoresistor signal

I suspect R2 is much too low; the 100 \$ \Omega \$ of the LDR is probably under high light condition, you probably have much less light. I suggest empirically choose R2 to center the A0 point with ...
BobU's user avatar
  • 127
4 votes

S8050 D331 base resistor calculation

Q1: is this the only way to go about it? Suppose a middle school kid is doing this for a science project, how does the kid understand which resistor to put where? Electronics requires knowledge, ...
jonk's user avatar
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4 votes

Why are vactrols not commonly used?

Vactrols contain cadmium, so it is not RoHS compliant.
Erik Vincent's user avatar
4 votes

Understanding basic photoresistor circuit

It's not clear from the datasheet exactly what kind of device you have. I've answered based on the assumption that this is a photodiode or phototransistor. First, a photodiode (or phototransistor) ...
The Photon's user avatar
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4 votes

What is the mathematical relationship between the resistance of an LDR and light intensity in lux?

Lux doesn't measure intensity, it measures illuminance. That means it measures how bright a light looks to the human eye. The relationship you are asking for will depend strongly on the wavelength, or ...
The Photon's user avatar
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4 votes
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LED light bulb is flickering when switched on

So the light turns off when the LDR is illuminated. Your first problem is you have to decuple the light generated by the lamp from the LDR - you set up what's known as a hysteric oscillator - light ...
MOSFET's user avatar
  • 4,633
3 votes

LDR / photoresistor issue: resistance is constant in different light conditions

Don't know if this is the cause of LDR failure, but your circuit has a basic flaw: A +12v supply can cause damage to the ATmega328, when the photo-resistor's resistance is low enough to raise the ...
glen_geek's user avatar
  • 26.4k
3 votes

Photo Resistor to Complete Circuit in Light

As others have correctly said, a photo-diode would be the right part. You can try something like this: simulate this circuit – Schematic created using CircuitLab You need to choose a suitable ...
TonyM's user avatar
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3 votes
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Photo resistor night light not working

You have the base of the transistor connected directly to the positive end of the battery. Pretty much the only way for the photoresistor to change the voltage on the base would be if the ...
JRE's user avatar
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3 votes
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how to wire together multiple photoresistors to make one big sensor?

I would take the following approach: Measure the resistance of one device with laser absent and laser present. You will have two readings. Mathematically model the circuit with all photo-resistors ...
Transistor's user avatar
  • 177k
3 votes

Light detection by GPIO raspberry pi

I would suggest you pull the gpio pin up to 3.3v using a sizeable resistor ,and then pulling down that same pin by connecting it to the collector here is a Quick solution , please calculate the ...
theCNN's user avatar
  • 37
3 votes
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Is there constant current flow in this circuit?

Yes, you are thinking correctly. It will draw some minute current, even when 'off'. The quiescent current would be that current going through the base bias resistors in the 'off' state. It would be ...
troubleshooter's user avatar
3 votes

Photosensitive Diode or photo resistor?

There are two modes of operation of a PD. A PD that conducts a current when reverse-biased and illuminated will produce a voltage across the terminals when illuminated. If you buy parts with proper ...
Spehro Pefhany's user avatar
3 votes

How to estimate the recommended current in an optocoupler?

All the parameters are measured at 5mA LED current, so that is a hint for a good value. As the transistor side is there to replace a push button, you just need to pull voltage as low as possible like ...
Justme's user avatar
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3 votes
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How to estimate the recommended current in an optocoupler?

The datasheet tells about the absolute maximum limit (50 mA for both), but I can't find any "recommended" current for things to work nicely. The data sheet states a couple of values (other ...
Andy aka's user avatar
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3 votes

Dark sensor with transistor

It does limit the current. When there is more current flowing via photoresistor, there is less current available from the 100k resistor R2. If the photoresistor resistance goes low enough to pull the ...
Justme's user avatar
  • 154k
3 votes

What is the mathematical relationship between the resistance of an LDR and light intensity in lux?

Typically the equation is \$\frac {\log(R_A) - \log(R_B)}{ \log(E_A) - \log(E_B)} = \$ k Where Ra and Rb are two resistances at illuminations Ea and Eb, and where the illumination spectrum is ...
Spehro Pefhany's user avatar
3 votes

How to test photo interrupters

The circuit seems to not respond. How would you expect it to respond? How can I check these photo interrupters? Insert an opaque object in the slot. The green LED is responding when an object is ...
Transistor's user avatar
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