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Hi folks,
I'm looking to see if there is a photoelectric sensor which works opposite to the ones normally fitted for out door lighting. The readily available ones normally operate dusk till dawn. But I require on that operates dawn till dusk.
The customer wants a machine to run during daylight hours only, but doesn't want the bother of a timer. The machine is located in a shed that remains dark all the time so I would like to mount a sensor outside.

I've searched online and they are available in the USA but have not come across any in the UK.

Any help or advise would be appreciated.

Thanks
 
Is the customer going to be in the room all day, if so surely a simple light switch would do.
 
Intoelectrics: What current is to be switched? What is the nature of the machine and hence load current ( ie: resistive , reactive, surge?). Such details are important in the selection of a reliable switching device.
 
Is the customer going to be in the room all day, if so surely a simple light switch would do.
No, its basically a compressor locked away in an outhouse on a busy farm. He wants it so it just comes on to top up the receiver tank as and when the farm staff use the air. What happens currently is that people just end up leaving it switched on and it then runs through the night especially if there is an air leak anywhere. I suggested a timer but he didn't like that idea because he just wants it running during day light hours and not any particular set time period.
 
Intoelectrics: What current is to be switched? What is the nature of the machine and hence load current ( ie: resistive , reactive, surge?). Such details are important in the selection of a reliable switching device.
The switch/sensor would not be subject to the load of the compressor as there is already a D.O.L starter and overload in place. I would just run it in place of the start button, in series with the stop button and ditch the hold in contact.
 
You will need to label up and have warning signs that the starter and compressor are remotely controlled, by what and where and when.

I reckon this remote control scheme is unsafe - it is so out of the ordinary to have some rotating machinery powered up only when there is daylight. There are other solutions - what about a 'first man/woman in' controller which energises the compressor for so many hours to suit the farm's requirement and then turns the supply off?

Schneider make a suitable DIN device but I am being harangued at the moment by my wife to cook tea which prevents me doing the search for it. What you want is the device which will take an impulse input, which turns on for a set period and then turns off - a bit like a staircase lighting controller but with a much longer timer.
 
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You will need to label up and have warning signs that the starter and compressor are remotely controlled, by what and where and when.

I reckon this remote control scheme is unsafe - it is so out of the ordinary to have some rotating machinery powered up only when there is daylight. There are other solutions - what about a 'first man/woman in' controller which energises the compressor for so many hours to suit the farm's requirement and then turns the supply off?
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I'm aware its a little out of the ordinary but I don't see a problem with it. There are many situations where rotating machinery is controlled and left to run automatically. In fact I did some install work on a factory where their compressor runs on a timer 24/7 .

It would be clearly marked up and with the appropriate isolation points & protection devices installed.
The compressor has already got a DOL starter & overload, pressure switch and pressure relief valve fitted and is sited inside a limited access locked shed.

The problem he has is that his staff get lazy or careless and no matter how often he points out that the compressor needs to be started and then stopped each day, it often gets forgotten about and then runs on through the night. I suggested to make one or two persons responsible for it, but managing it is difficult as his staff rotate their working patterns. At the moment he has to travel each day from his main site to go and check its turned off himself. You can appreciate its a pain in the backside for him so he asked me for possible solutions.

I just want to see what options are available before I go back to the customer with advice and a cost.
 
The switch/sensor would not be subject to the load of the compressor as there is already a D.O.L starter and overload in place. I would just run it in place of the start button, in series with the stop button and ditch the hold in contact.

The way you intend to wire-in the photocell (or my impulse timer relay) needs some more thought to ensure it all works as required including after power-cuts, the stop button is pressed, the overload operates. I suggest you draw out the wiring for what you propose and determine how it would function and then do the modifications I think are necessary. Perhaps you could show us for comment.
 
The switch/sensor would not be subject to the load of the compressor as there is already a D.O.L starter and overload in place. I would just run it in place of the start button, in series with the stop button and ditch the hold in contact.

The way you intend to wire-in the photocell (or my impulse timer relay) needs some more thought to ensure it all works as required including after power-cuts, the stop button is pressed, the overload operates. I suggest you draw out the wiring for what you propose and determine how it would function and then do the modifications I think are necessary. Perhaps you could show us for comment.
Yeah I see your concern, the stop button is an emergency type which locks off (mushroom type) and requires twist and pull to reset. The overload also has a reset button. I could maybe install an additional relay so in the event of a power cut the automation would have to be manually restarted I guess. I can't think of any other way to keep it as simple as possible.
 
I still do not like and I would not design using a photocell switch to control the power to machinery. The guru on the regulations for safely controlling machinery is darkwood - I suggest you contact him.
 
Regardless of how complicated or simplistic this is there is the issue you are upgrading the control system to a machine and with that comes personal responsibility, additional insurance cover requirements and a full documented risk assessment, also you will need to provide an updated wiring schematic for the new control additions as well as complying to the relevant regulations like the BS 60204-1 (2018), if you are on the ball already with all the above then fine and I will be happy to advise otherwise I would take a serious step back and think about it before doing any such work.

I would also question how controlling the compressor via daylight/darkness triggers is going to be practical. What about seasonal variations and the fact you gain and loose an hour during the year, are we to believe they only work until it gets dark?

He needs to buy a clip board and have a selected member of staff sign it off on his exit that a checklist has been done before leaving which would include switching of the compressor, I have been on over a thousand sites in my time and I have not heard about anyone having to put additional controls to a compressor due to staff incompetence, he needs to toughen up and be a boss, a clip board is vastly cheaper than upgrading the compressor controls and also he may gain a little more respect as a boss if he is seen to put his foot down.

Just my opinion on the info' provided, it just seems like the cart is leading the horse here when you have to make such decisions due to incompetent staff.
 
I love this!
I need a sensor that works the opposite to normal ones...
so, design the circuit, assess the load etc...
Is there a dusk to dawn sensor that switches "off" instead of "on"?
Yes...it has a relay...NC type...

Now, look at the load...
Beauty! I just need the normal sensor, then add the relay that can cope with the load...

To be fair, in a recent installation, my installer friend needed a window sensor that required a NC relay...a glorified reed switch...and had to order one from China...but it arrived, it works...
However, and not to detract from the learned opnions expressed previously, I am an amateur, an experimenter, and not an expert by any stretch of the imagination...
But it is fun!
 
Regardless of how complicated or simplistic this is there is the issue you are upgrading the control system to a machine and with that comes personal responsibility, additional insurance cover requirements and a full documented risk assessment, also you will need to provide an updated wiring schematic for the new control additions as well as complying to the relevant regulations like the BS 60204-1 (2018), if you are on the ball already with all the above then fine and I will be happy to advise otherwise I would take a serious step back and think about it before doing any such work.

I would also question how controlling the compressor via daylight/darkness triggers is going to be practical. What about seasonal variations and the fact you gain and loose an hour during the year, are we to believe they only work until it gets dark?

He needs to buy a clip board and have a selected member of staff sign it off on his exit that a checklist has been done before leaving which would include switching of the compressor, I have been on over a thousand sites in my time and I have not heard about anyone having to put additional controls to a compressor due to staff incompetence, he needs to toughen up and be a boss, a clip board is vastly cheaper than upgrading the compressor controls and also he may gain a little more respect as a boss if he is seen to put his foot down.

Just my opinion on the info' provided, it just seems like the cart is leading the horse here when you have to make such decisions due to incompetent staff.
I don't disagree with anything you said. It most likely will be the case that I just walk away. I just thought I consider all options available before I go back to him with what i'm willing to do.

Going back to the day light working thing. This is exactly what farmers do (well at least this one) they tend to work day light hours at this particular process.
 

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