Automatic Street Light

Thread Starter

ertiexd125

Joined Jul 4, 2010
16
Attach is a simple circuit for an automatic street light using LDR as sensor.
Can you suggest anything that could be an innovation to this circuit or anything you may think of that could be added to make it really innovative but the application will remain to be there which is lighting up the streets.
Help me please, ill be waiting for your replies.
 

Attachments

beenthere

Joined Apr 20, 2004
15,819
Using a voltage comparator would seem to make a simpler circuit. However, it appears you need a 12 VDC power supply for something like this to work.
 

t06afre

Joined May 11, 2009
5,934
Using 555 as a comparator/Scmitt Trigger circuit. Have not seen that for some time. But nothing wrong in doing it. As it is cheap solution working on a single supply.
 

Adjuster

Joined Dec 26, 2010
2,148
If you are using a 12V supply, then a 6V coil relay will need some series resistance. Without this, the relay is likely to overheat.
 

Bernard

Joined Aug 7, 2008
5,788
555 has been used this way before on AAC. If relay is 300Ω, then add a 300Ω, 1/2 W in series has been suggested. What are your lights?
 

DickCappels

Joined Aug 21, 2008
7,979
This is not particularly innovative, but you might want to add some hysteresis (such as an inverter from pin 3, the output of the inverter connecting to 555 pin 2 through a resistor) to reduce sunset flicker when the LDR sees the light come on.

Also, use a mechanical arrangement, such as a piece of opaque tubing to restrict the field of view so that other light sources do not affect the operation of the LDR -it is generally best to point the LDR toward the sky.

If the purpose of the lighting is to reduce crime, you can probably reduce power consumption by using a second timer between the NE555 (or comparator) and the relay so that the lights go off after being on for a fixed number of hours. This is ok to do in some places because in many places if not everywhere there are very few crimes committed in the hours before sunrise.
 

Thread Starter

ertiexd125

Joined Jul 4, 2010
16
thank you for the reply sir dick. I like everything you have said but my only problem is how can i begin your third statement you said that it would be better if i put a second timer on it so that in will switch off for a fixed number of hour. Can you give any similar circuit for the timer you are talking about or any ideas on how will i do it.
I hope to hear from you soon thanks for the reply.
 
Last edited:

Bernard

Joined Aug 7, 2008
5,788
Outline of possible turn off after 8 hours. 555 oscillator with period of about 56 sec, starts when IC 1-pin 3 gors hi, also releases reset on 512 bit counter. When a count of 512 is reached & inverted, AND gate is closed, inhibiting lamp drive. It's a start at least.
 

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Bernard

Joined Aug 7, 2008
5,788
I would use a CD4060BC as it has built in osc. & divide by 8192; for 8 hr clock period about 3.5 sec or pin 9, 7 uF[5-10], pin10 500k pot, pin 11 1 to 4.7MΩ. Invertors: 74C14, 74C914, 40106 schmitt triggers, or 4009, 4049. Diode[ 1N914 etc] AND gate as only one needed. Note: if sufficient temporary obstruction prevention is not provided at IC-1, a passing car light might reset 8hr timer, starting a new time period.
 

Thread Starter

ertiexd125

Joined Jul 4, 2010
16
I made my research and i also found that ic i'll post a circuit using a 5 hour time delay please look at it and tell me if its the one i need.
 

Attachments

Bernard

Joined Aug 7, 2008
5,788
Looks like a viable long time delay ckt. Relay closes at power-up, off at selected time or on closing Stop SW. Max time about 3.8 hr.
 

Thread Starter

ertiexd125

Joined Jul 4, 2010
16
thank you sir Bill for that reply and i will do that. Sir Bernard so the circuit will work fine on the application i am trying to do?
 

John P

Joined Oct 14, 2008
1,917
What is the STOP switch intended to do? In the diagram, it turns the relay off but doesn't affect the timing function. Also, the counter apparently keeps running continuously, so the relay will turn on after a certain time, and then off again, and on again. Wouldn't it be better if once the relay operates, it stays operated?
 

Bernard

Joined Aug 7, 2008
5,788
Here is an attempt a combining the two drawings.C2 as per Bill = 100uF. R5 & R7 To be determined when relay specs are known. At 555-8 it is a 4 way connection, dot missing. If short on times are selected, as John P mentioned. there will be reset problems, but at 8 hr. on, the sun hopefullu will rise within the next 8 hr. shutting every thing down- if not hit STOP. I would prefer a MOSFET forT2, then R5 =2.2k; R6 seems surplus.
 

Attachments

Bernard

Joined Aug 7, 2008
5,788
C2 with VR1 & LDR form a time delay. When dark LDR will have a high resistance, so C2 will be charged to around 9 V, with a spike in illumination, V at pin 6 will will attempt to rise as LDR falls,but must discharge C2 to 4V, 6V at pin 6, before 555 triggers. If LDR drops to 100k X 100uF = 10 seconds, but as C2 is not charged to full 12V, time will be a little less than 10 sec.
 
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