LED lighthouse

[madscientist]

I urgently need a circuit design. I need to power up 3 leds at 4.5v each. The leds need to be operating only in the dark. There are 2 sets of leds, they have to alternately switch on and off while operating (dimming in, holding and dimming out; one set on, the other off). There wont be AC source, so I have to use solar power to charge up the power source of the leds during the day. I was thinking of using NiMH batteries. Since this circuit will be used outdoors for a very long period of time, it has to be small, light and maintainence free. Personally, I have a tight budget and have limited access to specialized components. Seriously, I only know about soldering and nothing else on electronics. I hope you all can help me out, thanks. I have a maximum of 2 more days before the stupid public holidays arrive.<p>PS: Sorry for the bad english, :p

[Mike6158]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by madscientist:
I urgently need a circuit design. I need to power up 3 leds at 4.5v each. The leds need to be operating only in the dark. There are 2 sets of leds, they have to alternately switch on and off while operating (dimming in, holding and dimming out; one set on, the other off). There wont be AC source, so I have to use solar power to charge up the power source of the leds during the day. I was thinking of using NiMH batteries. Since this circuit will be used outdoors for a very long period of time, it has to be small, light and maintainence free. Personally, I have a tight budget and have limited access to specialized components. Seriously, I only know about soldering and nothing else on electronics. I hope you all can help me out, thanks. I have a maximum of 2 more days before the stupid public holidays arrive.<p>PS: Sorry for the bad english, :p <hr></blockquote><p>
Not sure where you are located but I'm fairly certain that your English is better than my version of your native language so it's all good.<p>Dimming in, hold, dim off... Dude... if you don't have ANY electronic experience you are asking for a tall order. Is this some kind of class project or a lawn ornament or what? <p>There are quite a few design elements here that would make this a fun project. Starting with your solar charging system. What's the insolation value for your area? How much room for batteries do you have? On and on..<p>You'll need to know what the wattage for the solar cell is. You'll need to know what the battery(s) is/are rated at in mAHr. You can't determine circuit power draw until you know what the circuit is or at least have an idea so you can't spec your solar and battery system until you design the circuit...<p>4.5V each means Vf is 4.5 volts? That seems high. Most LED's have a voltage drop of 3.0 - 3.5 V.

[philba]

yes, tell us what this project is about - what's the rush? 2 days is going to be tough even if you knew exactly what you needed to do.<p>you can do the flashing with a triangle wave driving the LEDs. I'd use two opamps and then driver tansistors. Not hard but definitely a challenge for some one with a "what's a resistor, dude?" electronics depth.

[Dean Huster]

I designed a lighthouse light controller for a guy a couple of years ago that did just that: ramp up to full brightness, hold for a bit, ramp down, hold for a few seconds, repeat. It was designed for an incandescent lamp. It satisfied his requirements perfectly, but not my curiosity. I wanted to add a "light bump" on either side of and during each ramp to simulate the effect of the lighthouse Fresnel lens as it sweeps. I laid down and took a nap until that idea went away.<p>If you want the circuit, I'll see if I can find it somewhere. Unfortunately, I lost a lot of stuff after a nasty virus and HDD format, so I may not have the circuit.<p>Dean

[josmith]

With your tight budget and short lead time I think you should cannibalize on of those $10 solar walkway lights for the solar cell, battery and on/off control circuit. <p>A basic stamp would do the dimming and sequencing. If you could get one overnignt you could probably figure out how to get it to do what you want in a day.

[philba]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Dean Huster:

...
I wanted to add a "light bump" on either side of and during each ramp to simulate the effect of the lighthouse Fresnel lens as it sweeps. I laid down and took a nap until that idea went away.
Dean<hr></blockquote><p>This should be pretty easy to do. There may be a way to do it in the triangle wave but anouther way is to use a second driver in parallel with the first and drive it with a pulse train that centers on the peak of the triangle. Then reduce the triangle a bit. of course, this isn't possible to do with a PIC...

[madscientist]

NE5U,
I am from Singapore, a little country whom escaped the tidal wave. Yup, it's some sort of school project. What's an insolation value? I have enough for 4 AA batts. I do not have a solar cell now, so I will be able to get what the circuit needs. the batts are 130AAHC 1.2V min 1250mAh standard charge 16 hrs @ 130mA. The storekeeper thinks that overkilling is harmless for the leds, I still prefer to keep it at 3-3.5 though, <p>PS: out of curiosity, what does your nick stand for?<p>philba,
I am trying to study the effects of strange light pattern on plants. I know nuts about electronics. Haha, strangly, I know a little about resistors, i tink i m a "what's a transistor?" guy.<p>Dean Huster,
go ahead and implement that light bump! i hope that that light bump doesnt exceed 1kg, :p virus and hdd format, my favorite.<p>josmith,
what's a stamp? getting a walkway solar lamp wont be an easy task in my area. pple here seems to trust batteries more than solar panel, hehe.<p>philba,
hi again, sounds easy, but i cant get a circuit for that. i m nuts about circuit stuff, that's y i m here, :p great! no pic, cos it isnt easy to find it and it wont be cheap here.<p>PS: for those hu are wondering y my replies are short, the reason is that this is not the first time I am replying to this post. The previous reply was lost with a exceeded 8 pictures limit, too much smilies, :p <p>Thank you all.<p>Cheers,
Rico<p>[ February 05, 2005: Message edited by: madscientist ]</p>

[jimandy]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr> I have a maximum of 2 more days before the stupid public holidays arrive. <hr></blockquote><p>You're from Singapore and you have a holiday coming up? Pray tell, what?

[madscientist]

pray tell what???

[jimandy]

What holidays?

[madscientist]

Chinese new year. So I have to settle this real quick! Oh gosh, today's the last day!

[josmith]

I didn't get that you were in Singapore around here the walkway lights are one of those hot items that go for under $10 sold just about anywhere.
A stamp is a pic that is pre programmed to take basic commands. The software along with the whole story is available free on www.parallax.com.

[Mike6158]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by madscientist:
NE5U,
I am from Singapore, a little country whom escaped the tidal wave. Yup, it's some sort of school project. What's an insolation value?<hr></blockquote><p>I am familiar with where Singapore is. I am thankful that you were missed. Your English is very good by the way... I wouldn't apologize for it if I were you. <p>Insolation refers to the amout of sunlight that your location has avaialble. It's related to lat/lon, average cloud cover, etc. For instance, here in Texas, in my location, the value is around 3.9 hours of "charging time".<p> <blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>I have enough for 4 AA batts. I do not have a solar cell now, so I will be able to get what the circuit needs. the batts are 130AAHC 1.2V min 1250mAh standard charge 16 hrs @ 130mA. The storekeeper thinks that overkilling is harmless for the leds, I still prefer to keep it at 3-3.5 though, <hr></blockquote><p>I think that the storekeeper is incorrect You can put as many batteries as you want on the project but if the solar cell charging rate and the amount of sunlight that is available (insolation) isn't high enough the batteries will eventually be discharged. Your circuit power consumption will be constrained by the charge rate that your batteries can take, the size of the solar panel, and the amount of sun that you have available to the solar panel.<p> <blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>PS: out of curiosity, what does your nick stand for?<hr></blockquote> <p>I'm a HAM operator. NE5U is my callsign. I chose it because it's easy to send with CW. -. . ..... ..- <p>Interesting... I have some boards ordered whose shipment will be delayed because of the Chinese New Year...<p>[ February 06, 2005: Message edited by: NE5U ]</p>

[madscientist]

NE5U,
it's tropical. I m pretty sure sunlight's aplenty all year round, Gee, I badly need a complete working circuit diagram now.

[Enzo]

Call signs start with N these days? I'll be darned. I gotta start reading more.