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slow on/off dimmer

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birdman

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is there anyone out there with knowledge of the building of the above subject?
i keep birds, and in the winter need a dimmer to simulate sunrise and sunset.
to switch a 100w lamp on in about 60-90 seconds to full power and by use of a timer switch it back of over a 30 minute period to darkness.
i have tried velleman kits, but you have to buy 2 kits at acost of £35.00
and i'm sure this is a rip off.
help? anyone?

birdman
 
I'd be inclined to tackle this one as two separate projects. One to control the power to the lamp (dimmer) by means of a varying input (DC, pulse width, etc) and the second to provide the ramp up, long dwell, then slow ramp down. A PIC or BASIC STAMP might be a good answer but I am a novice in that area.

A silly (or maybe not) idea - use a photocell mounted outdoors and an op amp or similar device to provide a varying DC signal based on outdoor lighting levels. It gets light and dark every day unless you are close to the poles. Use that signal to control the power to the light.
 
thanks for trying, but i'm looking for circuitry and parts, my problem is in the winter it is dark when i come home from work so i need light to extend the daylight hours to feed them.
and its dark in the morning when i go to work, so i need to simulate sunrise so i can again feed and water them.
i have no probs in the summer. only winter time.
can anyone put up some circuitry and parts?

thanks? :? :? :?
 
As its mains voltages (240VAC here in the UK!!!!) i'd be inclined to buy a pre-designed kit with a pre-made circuit board for the dimmer.

I know Maplins do a voltage controlled dimmer module and i think they're about a tenner so get one of those to fade the lighting.

Next.... Creating the control voltage. Well, ... this can be done in several ways, PIC (like Stevez sugested) would be ideal, but as your a new member i'm going to assume you dont have a PIC programmer, so its a hardware solution you need...

:?: :?: :?: :?: <ten minuites later> :?: :?: :?: :?:

What about a up/down counter IC (8-bit) and a (8-bit) DAC device?

The clock input to the device (clock frequency) could be set so that the counter moves up one step 0.04 seconds:

(90*60)seconds / 255 steps = 0.0472Hz

-- which is equal to 1 pulse every (1/0.0472) 21.2 seconds.

A simple 555 timer set as astable can do that easy - R1=300k, R2=3k C1=100uF. This would give 99% duty cycle, with a frequency of 0.0472Hz (on time is approx. 20.964 secs / off time is approx. 211.8mS)

Now place the counters' output value into the DAC to get a DC ramp voltage that will change as the counter changes. Feed this (via an op-amp to adjust offsets, and add a bit of gain etc) to the input of the voltage controlled dimmer module.

When the counter reaches its maximum value, we need to disable the clock.

When night comes, we then need to flick the count down switch somehow to tell the counter to count downwards, then restart the clock. The counter will count down, the DAC output will ramp down and the dimmer module will dim down.

Now who would like to draw the schmatics!

dimmer module is a fiver! bargain! (goto the shop, they will have them in stock or be able to get them)

**broken link removed**

** input is 0->10Vdc ... this is great, we can simply use a 5V full-scale DAC with an opamp connected to the output with a gain of 2.. easy!
 
kybert, thanks for your reply.
i've actually bought a slow on/off dimmer from maplins £16.99 but after i got it home ready to build i find out it as to be used in conjunction with another piece of kit!! this kit costing a further £15.00 the total being £32.00.
my point is i can buy a ready made unit from a avairy supplier for £45.00 and not worry about dry solder joints etc, i just thought if i had a drawing and a list of components it would be more satisfying that buying the kit or unit.
once again thanks mucker. :)
 
Do both,... Buy the kit i posted because lets face it, its only a fiver and thats well worth it and safer/easier than designing your own.


Then design and build the control logic for it yourself (or with the boards help)

That way you get a safe mains voltage dimmer, and a hand made, designed and built controller module.

Electronics is all about interfacing to other systems, if theres a cheep and reliable alternative to a solution, take it, and in this case i think £5 for a VC-dimmer is a blessing.

Many projects i design for at home often cannot be built for anywhere near as cheep as i could buy a pre-made device.
 
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