My College Project

[cherryman]

Hello,

I have been given a project to design and create an automatic lighting circuit for a room that utilises a PIR sensor to activate lights(flourescent tubes). The idea is that after 30mnutes the lights dim or 1 of the 2 tubes within light are turned off to give a warning signal that the light will then be turned off in another 20mins. This lets anyone in the room know that they need to reactivate the PIR sometime in the next 20mins so they can carry on working.

What would be the easiest way to design the circuit? Have 2 seperate timers for each lighting strip or I have been advised about using 4bit counters?

What components would i need? if anyone could help with a circuit design/diagram as I am struggling to create a solution.

Thanks for your help.

 

[Knobhead]

Off the shelf timers are the practical way around it. Bespoke gear is OK until it goes wrong and has to be repaired.

 

[Spoon]

It really depends on what you are looking for. It would be easy to wire up an alarm PIR to two timer relays, which control a light each, but do you want more for you school project, so that you get extra marks? As far as I know, you cant dim flourescent tubes, but if you can then im sure someone will put me right on that. If you do want to dim the lights I would use incandecent bulbs.

 

[stuart569]

Course you can.Dimmable ballast is needed though or complete fitting.Used them before.Not cheap though and they had a fancy elv electronic type dimmer
Digital dimmer i think you call them.Was a couple years ago

 

[Marvo]

Are you expected to design and make timers from components or can you use standard off-the-shelf timers?

 

[cherryman]

Are you expected to design and make timers from components or can you use standard off-the-shelf timers?

I can use off the shelf timers as far as i'm aware, but i would need to be able to explain what is happening with the timer, so to design and make would be ideal. i would ideally make as cheap as possible, so have 2 relays on 2 different light strings would be the easiest way?

 

[Spoon]

Off the shelf items would be easier, but more expensive than designing your own. If you do design your own you will have more control over how you want to operated the lights. You could make the first one flash rather than go off for your warning light. Will you be using mains for the whole circuit?
The easiest option is to buy a ceiling mounted PIR. I've seen these in CPC for £27. TIMEGUARD|SLW360|360 DEGREE SURFACE MOUNT CEILING | CPC as an example. Then find two 230V relay timers. each that you can do the times you want. The signal from the ceiling PIR will activate the timers. Are the times you mentioned in the OP set in stone or can you choose your own? The manual on the timer relays will usually describe how they work.

 

[HandySparks]

If I was doing this for real, rather than an educational project, I would just put half the lights on a PIR with a 30 minute timer and the other half on another PIR, located alongside the first one, with a 50 minute timer.
Ideally the timers would be integral with the PIRs, but you might struggle to find one that will do a full 50 minutes.

 

[Superspark23]

Thorlux have lights where each light can be programmed to dim after so many minuits and and completely off later on, each one can be interlinked with a 12v smart line. You can then use the inbuilt PIRS or have seperate ones near doors. might be worth you reading about them.

I think theyre called thorlux kanby t5 smart

 

[Marvo]

Thorlux have lights where each light can be programmed to dim after so many minuits and and completely off later on, each one can be interlinked with a 12v smart line. You can then use the inbuilt PIRS or have seperate ones near doors. might be worth you reading about them.

I think theyre called thorlux kanby t5 smart

For a college project I can't help thinking this might be cheating

 

[Superspark23]

Not really lol it gives him what he's been told to design plus being t5's he's thinking of energy efficiency aswell as these lights can be dimmed all the time saving more energy.