not for cnc but need help with 555's

[kaighn80]

i know its not a cnc problem but i think that i'm more likely to find some one here who will be able to help me. what i want to do is build an led fishtank light but i want to simulate sunrise/sunset, so far i think that my best bet is to use 555 timers and daisy chain them so that they each trigger the next but i need a diagram to do this as i have no idea about building electronics from scratch i can however follow a diagram, any one help please?

[doorknob]

Can you clarify the effect that you are looking for?

Is your goal simply to turn on the LEDs after a certain delay period, leave them on for a specific time, and then turn them off for a specific period (and repeat), or,

is it to ramp up the intensity of the LEDs over a period of time to simulate sunrise, eventually reaching full intensity, leave it at that intensity for a period of time, and then ramp down the intensity to simulate sunset,

or something else?

Also, are you looking to vary the LED intensity by pulse-modulating the current that drives the LEDs and varying the pulse duty cycle or frequency, or some other method?

And, are you looking to use an array of ordinary LEDs that are typically used as indicator lamps, or do you plan to use high-intensity white LEDs that are used for flashlights?

[Al_The_Man]

How many LED's are you using, if several or more than one you could set up a time of day timer which would trigger a pulse chain that inputs to a BCD or Binary output IC.
This would count the light up to full on and just before switch off count down to off?.
The IC's to do this are relatively cheap.
There are probabally a few circuits out there on the net, and/or pick your self up a Logic IC cookbook that should steer you in the right direction.
Al.

[kaighn80]

Originally Posted by doorknob Can you clarify the effect that you are looking for? Is your goal simply to turn on the LEDs after a certain delay period, leave them on for a specific time, and then turn them off for a specific period (and repeat), or, is it to ramp up the intensity of the LEDs over a period of time to simulate sunrise, eventually reaching full intensity, leave it at that intensity for a period of time, and then ramp down the intensity to simulate sunset, or something else? Also, are you looking to vary the LED intensity by pulse-modulating the current that drives the LEDs and varying the pulse duty cycle or frequency, or some other method? And, are you looking to use an array of ordinary LEDs that are typically used as indicator lamps, or do you plan to use high-intensity white LEDs that are used for flashlights?

sorry should have made it a bit more understandable, what i hope to do is have led's in banks or strips, that will turn on in sequence then stay on for a predetermined amount of time ie:8 hours, then turn off one by one in sequence, i'm not worried about an accurate simulation just yet i just want something that resembles the effect, i intend on using a mix of colours with mostly white/bluewhite but will include green, red and uv. for the min i'm doing this on a shoe string, so the led's will be replaced as and when funds allow.

[kaighn80]

Originally Posted by Al_The_Man How many LED's are you using, if several or more than one you could set up a time of day timer which would trigger a pulse chain that inputs to a BCD or Binary output IC. This would count the light up to full on and just before switch off count down to off?. The IC's to do this are relatively cheap. There are probabally a few circuits out there on the net, and/or pick your self up a Logic IC cookbook that should steer you in the right direction. Al.

something like this would be great but i think it may be a bit beyond my designing or understanding skill.

[doorknob]

The key is to break down your desired behavior into simpler functional blocks.

For example, one block that you need is a night timer with the ability to be triggered and then perform a time delay for 16 hours, after which it can shut off and trigger a day timer and a LED ramp up circuit. The day timer needs to be able to be triggered and then perform a time delay for 8 hours, after which it can shut off and trigger the night timer and an LED ramp down circuit.

So, you may be able to simplify things further by figuring out an 8-hour timer circuit as a basic building block, and then figure out how to either use multiple ones or reuse a single one to get your desired day and night timing requirements.

555 timers may not be stable enough to reliably do an 8-hour time delay with a single timer, so it may be necessary to build the 8-hour delay out of a couple of timers. You can probably find some suitable long-delay timer 555 circuits on the net. You will have to decide whether you want a "one-shot", triggered timer or a free-running, repeating timer (you could probably design it either way).

Independently of the 8-hour timing block, you can work on a separate LED ramp up or ramp down circuit block which can be triggered by an external signal. First you need to decide on the timing for the ramp up/ramp down - for example, maybe you want five minutes between each step on the ramp - then go ahead and make a repeating timer with a five-minute time delay. Once you have that, then you need to figure out how to turn the LEDs on (or off) one LED at a time for each five-minute cycle. That would probably involve a separate circuit block made up from a BCD counter and LED driver (or you could even separate that into a BCD counter block and an LED driver block). You also need to figure out how to turn off the five-minute timer once you have turned all of the LEDs on (or off). You also need to figure out how to trigger the five-minute timer to start timing. And you need to figure out how to switch the BCD counter from counting up at sunrise to counting down at sunset. You will probably want to learn how to use a "flip flop" circuit to alternate states between ramp up and ramp down, and/or learn to use simple logic gates for AND and OR and NOT logic.

So, once you break it down like that, you will have a small set of building blocks to figure out and experiment with, after which you will just connect them together, and voila you have a working sunrise/sunset system.

[Al_The_Man]

If you want to by-pass the design and building stage using logic IC's, another option might be a Smart Relay the likes of Siemens Logo, there are quite a few different makes that are the same but re-labeled.
It is a miniature PLC (Programmable Logic Controller), they come with a real time clock, which you are probably going to need anyway.
The nice thing is if you screw up you just have to play with the instructions set until you get the program to work, no rewiring etc.
They can also be had on ebay a bit cheaper.
Al.
.

[mike_Kilroy]

Originally Posted by kaighn80 i.....what i want to do is build an led fishtank light but i want to simulate sunrise/sunset,

How about a different approach/idea? I have a friend with a beautiful fish tank set up with LED liting and dusk/dawn, etc, etc, etc.... I showed him x10.com

Here you can buy little $ 5/10 sensors that sense dusk/dawn, turn led liteing on/off accordingly with little $ 5/10 modules pluged in with liteing pluged into them. add a complete controller with timers, sensors, etc etc that can effects, dimmers, etc for a few tens of dollars more... cm15 it is called for the controller that you program with computer then it is stand alone unit. add security sensors for $ 5/10 each and add an alarm to your house. turn the coffee pot on in the morning just before you get up.... all on the cheap.

anyway you may find their stuff for $ 50 for a batch of sensors and controllers is just what the fish ordered.