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MAKING A LIGHT / DARK SENSOR A Simple and Cheap Dark-Detecting LED Circuit | Evil Mad Scientist ...

Lyn your question has at least two answers going by my experience. The search engines are now geographic sensitive judging by how different the results are even for a single word but depending on where the searcher is located. This may be useful if you are looking for a local retailer but not so useful if you are looking for a tech paper fron another country but not when you do not know where the source of the data is located. The problem is further compounded when you are looking for a product which is sometimes handled by a national chain store as well as by the manufacturer.

Scientific papers which is sometimes published as well as summarized by another source but you only know the subject matter not the author also confuses the search engines when you only have one word as subject reference. My latest confusion on this was regarding positive grounding. It took a long time before I found a decent tech report instead of marketing bumf. However when I attempted to copy the link to the first website using the same key words I was unable to return to it. Going to the history was no help because I had followed highlighted text through several website.

Sometimes I think these search engines are a bit too smart.

Is nobody capable of independent searches?
Obviously not!

I used to, but found out it is easier to just sub the job out.

I for got that I'll be using a LDR to sence the light. Could i just use one of the small cir, on the net that uses a npn tran. but instead of switching the relay,use it to feed the TIP120?

Why would you want to make one. You can buy it here for $10.00.

http://compare.ebay.com/like/360449077711?_lwgsi=y&ltyp=AllFixedPriceItemTypes&var=sbar

Hi Wareagle. I think that I found one on ebay,but it says it will handle up to 35 watts,so I figured out my led FC is about 1 amp x 12vdc = 12 watts. guess thats how you figure it out, so it will work and its only about 5 or 7 dollars, and yes it is cheaper to buy it, BUT it is also FUN to make the thing your self, well for me it is.

tks John

conntaxman, Sometimes I think that posts are read without fully understanding the nature of the post. My understanding is that you want a simple circuit using components that you already have to enable you to achieve a better understanding of the circuit and to learn and have enjoyment form such a project. Unfortunately I cannot help but do have empathy with your request.

Think of the search engines as dictionaries - if you do not know how to spell a word, how can you look it up? If you do not know the word for the search engine, how can you search?

In the first circuit Lyn pointed to:-

Simply put your Darlington in place of the single NPN, and, put your load in place of the relay.

10W generates a lot of heat weather it be BJT FET or thyristor donno about Darlingtons

you need to design a proper heat-conductor/air-cooling structure the last is thermodynamic (F it's thermodynamic ... sh. (what is it)) fluid dynamics gas dynamics (J i don't remember what the discipline was) ... anyway you dont figure that 1 out from the scratch

(your components overheat burn down or get rapid aging cycle)

also you dont want to burn LEDs at nominal Max nor pulsed Max

the efficient way was to have more LEDs at ?? half power (whats it in english...) ? half-life the period they get half dimmer (i ran Red-Led for a light switch - and it was about the year from dark to sunrise 365.2425 dpy (then it didnt look so cool))

if it's an outdoor stuff it futher complicates your heat off-lead network + environment resistance requirements (if it forms condensate it gathers grease forms a layer of sh¡t on the PCB (the scanvaegt had a neat production scale case design resolving many of these issues))

anyway solutions for complex problems are genuine and simple (and doesn't always need to have 6y warranty)

relays tech spec http://www.ia.omron.com/data_pdf/data_sheet/my_dsheet_gwj111-e1-03.pdf

((studied/)glanced@ the model MY2K) 2 000 000 cycles with your power profile - but i don't see the hold-state current/power numbers 110mA for hold@set is a-bit of a waste for alternative NRG circuit using 800mA

Why go through all that trouble if you just want to locate where switches are in a dark room?

You can just replace those wall toggle switches with the type that has a built-in neon lights? The built-in neon lights will be ON and visible whenever its dark in the room and the wall switch is in OFF position.

I know you would like to make the circuit yourself but there are reasons that you should consider using a store bought controller. The solar controllers on Ebay & other places control the charging rate of the battery to stop over charging. They also control the output of the battery stopping the battery from discharging below a preset voltage, this will extend the life of your battery as over charging & over discharging can shorten the life of the battery greatly.

These controllers also senses the solar panel output to turn on lights when it gets dark & have a built in timer that can be set to turn off the light after a set time that is programmable. These controllers can be purchased for about $10 to $20 & give you a system that will last a lot longer than if you just have the solar panel & LED with a light activated switch directly connected to the battery.

Making the circuit yourself may be fun to experiment with & I would encourage you to experiment with electronics to learn all you can. But in the long run the cost of replacing the battery every time it dies from being completely discharged & then possibly over charged will make it a very expensive project if you want to use it as a permanent setup.

I have just recently been through the process of rebuilding a system similar to what you want but a bit bigger 10 X 10 W LED's like you have . The person had not bothered to use a controller on their system & they had paid over $400 for a 110 Ah sla battery that should have lasted 4 or more years but the battery died in under 12 months of use from being completely discharged & then possibly over charged on a regular basis, a very expensive lesson all because they didn't set it up correctly.