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Converting LED to Street Light?

Paul Saha

Jul 7, 2016
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How to covert the LED in the circuit to street light for consumer application?
 

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Gryd3

Jun 25, 2014
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How to covert the LED in the circuit to street light for consumer application?
This is better than what is currently used?
You looking to sell to home-owners or cities?
Do you have any experience with electricity? (Voltages over 24V)
 

Paul Saha

Jul 7, 2016
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Yeah, its the simplest circuit.
No I am not going to sell anyone.
It is a genuine question of, what if I want to use this in real life?
No I don't have any experience with electricity over 24V.
 

Alec_t

Jul 7, 2015
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How to convert the LED in the circuit to street light for consumer application?
You would have to replace that little LED with an array of high-power LEDs and use a totally different circuit with components rated for mains voltage. Not something to be attempted if you are not experienced with high voltage circuits.
 

Alec_t

Jul 7, 2015
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what circuit should i use?
You shouldn't, since the required circuit involves high voltage.
The commercially available high power LED drivers would likely be off-lline SMPS devices providing constant current.
Your circuit has no hysteresis, so the LED would flicker madly at dawn and dusk. It would also be inefficient due to energy loss in the resistor in series with the LED and in the transistor when neither fully on nor fully off.
 

Gryd3

Jun 25, 2014
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The circuit you shared with us works well enough for this low powered LED... but things get complicated when you ramp up the current required, and then even more complex when you want to use it with AC.

The transistor in your circuit will not cleanly switch. As the LDR changes, the transistor will gradually change from it's off-to-on states. To do this, it passes through a 'linear' region where it's part-way between on and off... kind of like a dimmer.
The problem here is that the 'power' rating of a transistor is quite low, so if you had tried to control a high-powered LED with it, it would heat up an incredible amount and may even *pop* as it begins to pass through this 'partially' on state.
So... the first thing you would need to resolve is how fast the device changes between on and off to avoid spending time in this 'linear' region.
The second thing to consider has been mentioned already, and is 'hysteresis'. If you have an Air-Conditioner and a Heater both set for 70degrees ... which one would be running? Hysteresis allows for a sort of 'dead-band' so the temperature (or light level) needs to either be *above* or *below* a set point. If the current level is the same as the set-point, it simply does not change until the current level is either higher or lower.
This will prevent the device from flickering on/off as it begins to change. I'm sure you have noticed that those inexpensive night-lights sometimes flicker a little.
The third thing to consider now is the voltage, and type...
The sample circuit used 9V-DC... but a mains powered circuit would run on 100-240V AC @ 50-60Hz ... Your sample circuit would not operate when you reverse the voltage... so running it on AC would be troublesome considering the voltage alternates forward and back many times a second. The voltage level itself also poses a serious safety hazard, but can be dealt with simply by using higher rated components and *never* working on it while it's plugged it. Care must also be taken to ensure that absolutely no part of the circuit is exposed to prevent electric shock!

In any case... you had asked a question looking to learn.
You should take a look at an 'SCR' and 'Triac' as replacements for the transistor, but you can also use a Relay.
As far as introducing hysteresis is concerned, there are special ICs dedicated for this and they often correct the switch on/off time problem at the same time. Do a little googling to figure out how it works and you can logically build an 'ideal' circuit.
 

hevans1944

Hop - AC8NS
Jun 21, 2012
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It looks like you want a "street light" that turns on at dusk and turns off at dawn and operates from AC mains power. Plenty of these lights already exist on the commercial market. Some even have passive infrared (PIR) motion sensors to turn the light on during the dark time, thereby saving a lot of electricity lighting up an area where no one is present. Your "proof of concept" circuit is a good start toward understanding the requirements of a dusk-to-dawn street light application. It satisfies the three design considerations listed below to demonstrate proof of concept, but it is not suitable for control of a higher intensity light.

what if i use a tubelight?
If you mean a tubular fluorescent light with a ballast, these are not generally suitable for outdoor lighting because they are difficult to start at low temperatures. An electronic ballast can help alleviate starting problems, but why would you choose a tubelight is lieu of any other luminary, such as an incandescent lamp, a white-light LED array, a low-pressure sodium-vapor arc lamp, or a mercury-vapor arc lamp? Any of these can be operated from relay contacts with proper supporting circuit designs.

So, to continue your public street light design effort, you need to consider how you will implement the following three requirements:

(1) You need a power source. Clearly a 9 V battery is insufficient. A mains power supply is required. You need to specify the power and voltage requirements of the luminary you choose.

(2) You need a means to control power to a large, powerful, luminary suitable for use in a street light. Perhaps an LED array will suffice, but you need to specify the luminary you intend to use. This control should be efficient and not dissipate a large amount of power. A BC547 with a current-limiting resistor is not going to work for reasons others here have mentioned. Since this is an on/off application, a relay might be the best approach, along with appropriate control circuitry. Other solutions for power control are also possible, such as TRIACS, SCRs, IGBTs, and MOSFETs. You, as the designer, must decide which method of power switching is appropriate for the luminary you choose for your street light.

(3) You need some means to sense when dusk arrives, and perhaps the same means to sense when dawn arrives, to control when the street light turns on and off. A light-dependent resistor (LDR) may or may not be the best choice for that, but they are commonly used for this purpose. This device will serve as an input to (2) above, which as previously mentioned by others here, will implement hysteresis to prevent unstable operation when transitioning to dusk or dawn..

Good luck proceeding from your "proof of concept" circuit to a practical and efficient street light. It will be an interesting journey and you can learn a lot by studying how it has been done by others. Google is your friend for this.
 

Paul Saha

Jul 7, 2016
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I tried using a relay, but it still doesn't work. (Not a tubelight but a Led for now!)
Can you please look at the attached circuit?
 

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Gryd3

Jun 25, 2014
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I tried using a relay, but it still doesn't work. (Not a tubelight but a Led for now!)
Can you please look at the attached circuit?
Please share details of your relay.
You don't need to connect the switching side and coil side.

Simply put your battery, resistor, and LED in series like you normally do, but insert the relay in-line somewhere. Use the 'common' and 'NO' contacts.

Keep in mine that the 'NC' contact will go 'open circuit' once the relay triggers... so you *can't* use the NO and NC at the same time to make a circuit.
NO and NC are often used at the same time to 'toggle' between two outputs...
 

Sunnysky

Jul 15, 2016
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remove relay and 9V and connect LED + 220R to 5V and collector. Anode to 5v and use two NPN in Darlington mode.
 
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