So I found this circuit after months of searching online. The output only powers a 6V bulb though. Can someone tell me how I can make this power 12V? Is there some sort of relay circuit out there that I could hook this up to and still make it dim?

here is the link to the circuit- http://www.chemical-ecology.net/papers/aesa83.htm

I need this circuit to somehow have an output of 12V (a little less would be alright) and be able to control 8amps. This will be running a total of 33 lights in series of 3's with 11 parallels. The specs of the light are forward voltage of 3.4 at 700mA.

If this is not possible to do or I am going in the wrong direction please let me so I can stop trying to make this happen.

Thanks

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aesaf1.gif (15.0 KB, 47 views)

 

This didnt really take you months to find right?

3.4 @ 700mA sounds like a lumiled type LED. This circuit posted cannot deliver 8 amps nor at 12V so I wouldnt use any part of what you posted.

LED's are best controlled with current not voltage.. please consider this as paralleling LED's makes for an unhappy user and a circuit re-design. In my opinion, I would throw out that circuit you posted and design from scratch.. it can be done at about the same cost as the circuit you posted. I'll design it for you if someone else doesn't provide a solution you're happy with.

 

Does it sound like I have no clue what I am doing? I think it actually did take me months to find that circuit. I couldn't find anything that did the sunrise and sunset in one diagram. I attached a schematic for driving the LEDs (and yes they are luxeon.) The schematic is rated up to 5A so I was thinking of connecting either running 5 series on one and 6 on the other or doing 3, 3, and 4. In place of R4 I am trying to find a circuit or maybe just one component that will slowly turn the leds on from 0-100% over an adjustable time when power is applied and then will go from 100-0% when power is turned off. I have made this circuit and it works well, so now I am trying to move on to the next step of the slow on slow off. Whatever you have I am ready to try. My electronics knowledge is at a minimum, but I am willing to learn.

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FXFH3K6D55EWIFO8K4.MEDIUM.jpg (25.6 KB, 27 views)

 

Hi Rye_84,

The supply voltage and the resistive divider determine the output
voltage of the circuit. (12 volt supply voltage and two 30k resistors.)
Therefore if you increase the supply voltage to 24 volt the output
voltage of the circuit will increase to 12 volt.
But there's a small problem, there allways is . . .
If the load gets 12 volt the transistor also gets 12 volts across it's
terminals, multiplied by the output current and it gets hot !
This may not be a significant problem when using this circuit at 12
volt but if you power it with 24 volt . . . and it's a waste of energy too.
However you could connect a second load in series with the collector
of the transistor, the transistor would only heat up during sunrise and
sundown. During the night no collector current, during the day (virtually)
no collector emittor voltage and therefore no dissipation in the transistor.
Personnaly I would replace the 741 with a fet input opamp with a higher
output current, this is needed to drive the transistor in or close to the
saturation region.
And why did the original designer didn't think about this ?
Because he's an idiot !
You might not get the result you expect because a led is not a lightbulb.

on1aag.

 

The latest circuit you posted looks much better in my opinion. The current through the LED's is current limited and that's good. I'm not familiar with that regulator but consider the power dissipation it will have with a maximum input voltage.

On to the slow on & off part.... can you better define what you want? Do you want your LED's to slowly turnon as soon as there is ambient light and turn off when there is none... or do you want them to be on in a proportional amount of the ambient light? This would cause them to slowly turn on and off at the same rate the ambient light increases/decreases.
You may be able to fit a light dependent resistor in there.. or do you want something more sofisticated?

Not sure what you are after.. try and describe the effect you want exactly..

 

This is a rough outline (I'll probably use the Op Amp as an integrator in the final) of how I would do it.

But, in order to fill in the details I need:-

1. a data sheet for the LEDs
2. the time delay that you want. ie. how long to rise & how long to set?

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Sun rise - set.gif (36.5 KB, 20 views)

__________________
Len

 

What I want to happen is when power is applied to the circuit the LEDs will start at 0% and slowly make there way up to 100% and stay at 100% until power is turned off. When the power is turned off they will slowly begin to fade back down to 0 and stay there until power is applied to the circuit again. Does that help?

 

If at all possible I would like the rise/set to be variable between a half an hour to an hour and a half. If that is not possible an hour or an hour and a half would be fine.
Here is a link to the specs of the LEDs-
http://www.lumileds.com/pdfs/DS56.pdf
I will be using the cool white and royal blue LEDs and would like to run them at 700mA.

 

I'll post a circuit tomorrow.

__________________
Len

 

Yes it does.

30 min to 90 min is no problem, but it will have to be a digital circuit (a counter arrangement) as 90 min is a bit long for an analogue timer.

Questions:-

When you said "power on/off" do you want it to switch the mains power on when the start button is pressed and switch the mains power off 30 ~ 90 min after the stop button is pressed?

Or do you only want it to switch the 12 Volt on/off?

Would you prefer a toggle switch for on/off rather than 2 buttons?

__________________
Len

 

the main power source is a computer power supply. I was only looking to switch the 12V side on and off.

I think I toggle switch would be better.

 

Attached is the digital part. It is a variant of a circuit I designed for a friend.

I'll post the LED driver part tomorrow.

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30~90 min Timer.gif (15.4 KB, 18 views)

__________________
Len