Grow Light Day/Night Cycle

[malfist]

I'm working on a grow light, and the plants need a night cycle of ~ 8 hours. What can I use to time 16 hours, and 8 hours? 555's won't cut it.

 

[kchriste]

Usually you can get those programmable 24hr plug in timers.
BTW, the police are on their way.

 

[malfist]

haha, I love growing things and have been trying to spice up my dorm room with herbs and some veggies. The sad thing is, almost all the information on LED grow lights either come from some place trying to sell you an overpriced kit, or mary jaine growers. I even saw a how-to on converting a spare dresser into a hidden marijuana grower (using CFL's).

I've been trying to grow mint and radishes, and my current setup isn't powerful enough.

 

[Vizier87]

probably if you have can hack a digital alarm clock which goes off at those specific times, wire the speaker output to feed to a latch which turns on a light driver?

 

[arunb]

you could use a micro-controller such as a PIC (see Microchip Technology Inc. is a Leading Provider of Microcontroller and Analog Semiconductors, providing low-risk product development, lower total system cost and faster time to market for thousands of diverse customer applications worldwide.), the 16F690 could be a suitable choice for your application.

But then you would need to know programming in assembly or C and also some basic soldering skills. There are numerous PIC based clock projects in the internet from which you could ideas.

From in the info. you posted, I think you need a PIC connected to a watch crystal (or a dedicated RTC chip if ), and a relay to control the light.

See this link they may have a suitable kit which you could modify. https://www.sparkfun.com

 

[vne147]

Unless you're determined to build it yourself just so that you can have a project (which I completely understand), here you go 7 Day Programmable Digital Timer - Controls And Monitors.

 

[malfist]

I'd rather not use a microcontroller, it seems like overkill. I do know how to program however (I'm primarily a programmer, hardware is only a hobby).

I think I'm gonna go with the first suggestion, it makes a lot of sense, but if I wanted to do dimming to match fading sunlight I'd probably have to use a microcontroller.

 

[audioguru]

A CD4060 and a CD4541 are an oscillator and a digital divider. They make very good timers.

 

[BrownOut]

A PIC would be easiest. But building an electronic solution sould be easy. Just use one of the counter IC's such as the 4060. Set the input oscillator to a frequency that gives the maximum count in a 24-hour period. Do a D/A conversion of the low order bits to get the fade in/fade out effect, or else convert those bits directly to a PWM signal. It's just a logical puzzle, but a smart college guy can figure it out

 

[Hero999]

You could add an LDR so it's synchronised to the natural ambient daylight, then you can set the minimum day length.

 

[malfist]

What is an LDR?

 

[vne147]

Light dependent resistor also called a photoresistor.

Photoresistor

 

[smanches]

MJ growers are the best indoor growers in the world. I would just find some forums and learn what they do.

Don't worry about fading the light. Don't use LEDs as they do not have broad spectrum light, and are way more expensive than florescents. Unless you are going to let the plants go to seed, just leave the light on all the time. They do not need the darkness when doing solely veg growth, only when flowing/seeding.

 

[Speakerguy]

Yeah, I knew this guy wasn't an MJ grower when he talked about wanting to turn the lights off. I think the MJ growers leave them on 24/7.

Power compact florescent bulbs are a good technology. I used them over my 55 gallon planted aquarium and they were plenty. I would just get a commercial power compact fixture and use the light timers available at the local hardware store.

 

[mbarazeen]

you have to use a high frequency crystal oscilator and a divider if you want to get good accuracy. i remmeber i have posted a diagram long before for some timer for LED control, that gives 1 sec pulse, this can be fed to a divider to get 8 hr, then after 8 hr count it can set the reset of counter via another counter that will enable the reset after 16hr (8hrx2) count. then it will reset after 8hr. if you need complete circuit i can post shortly.

 

[mbarazeen]

see the attached time base, hope it will give a single pule after every 8hrs, if any one can simulate it? also hee needs 8 hr then 16 hr signals, so the out put can be fed to a 4017 and to some logics to work as required.

Edit: .made a mistake connect U1A to pins 13 & 6 of last IC, resets can be done using the free pin(now connected together) of AND gate inputs for last two steps and the 1st ICs direct input.

 

[Hero999]

I don't see why you should need to simulate it, if your logic is right then it should work.

I have two concerns:

There are no decoupling capacitors, there should be a 100nF capacitor across the supply pins of each IC.

What's the supply voltage?

The CD4060 might have a problem counting 3.768MHz if the supply voltage is too low.