Anyone who can help me with a school assignment question

I have attached a picture. I just need to know if the option I've chosen is the correct one and if possible an explanation too. thanks

Yes, you are correct.

Initially the lamp is off and the lamp contact is open.
Pressing start on its own energises the start contact and the lamp does nothing as the stop contact is open.
Pressing stop on its own energises the stop contact and does nothing as the start contact is open and the lamp contact is open.
Pressing both start and stop together makes the lamp come on and the lamp contact close.
Releasing stop first will cause the lamp to go off.
Releasing start first will leave the lamp on as the lamp contact is around the start.

Thanks a lot for the explanation.

And if you would want to correct the setup in order to be useful, the stop-button should be wired as normally closed (NC). I would also like to rename the stop button alias to StopOK, to indicate that it is a required input and not a mistake that it is added as XIO (normally open, in case I'm not recalling A-B naming correctly)

CommissioningMan said:

And if you would want to correct the setup in order to be useful, the stop-button should be wired as normally closed (NC). I would also like to rename the stop button alias to StopOK, to indicate that it is a required input and not a mistake that it is added as XIO (normally open, in case I'm not recalling A-B naming correctly)

Click to expand...

I would name it Stop_PB as thats what it is.

Is there anyone on the planet that would see a XIC stop button and think it's a mistake.

I too often see the opposite "mistake" of not safe wired stop or limit switch circuitry that perhaps could have been prevented by the name StopOK being used prior to the el. dwg. I see both names being used.

Yes I think is is a poor example, the stop should be N/C, as LD has posted, the only way it could work is if the buttons (or switches) were retaining, then you would not need the latch, however, this is a no no, using both normally open contacts will work but the Stop in the code would have to be N/C so pressing it would effectively open the N/C contact de-energising the circuit.
The problem with this is that if the wire dropped off or the contact of the stop button failed open then the output would fail to turn off, normally not what you want.

you are correct. as everyone is saying the stop is usually a nc contact. the only time i have seen it done like this is when it is used on a deadman switch that has to be pressed for the circuit to work. it is a terrible and slightly confusing example to give someone who is starting.

It's amazing how the old adage of "those that can't do or manage, teach" is right...

The best one I've ever seen was from a friend of mine teaching basic electricity and the example he gave to control the light of an LED was to parallel a potmeter with the LED... when I asked if he'd ever seen it work he confirmed that it worked in the lab. No thought given about the behavior of the power supply (which would have had short circuit protection) when trying said experiment.

Not knocking all teachers, but there have been a few situations I have come across, one was very much like the above, probably the worst was my youngest daughter was struggling with her maths, not that I'm that good but she came home with about 10 old GCSE type exams, the teacher had downloaded some old papers as a test for the class, there are a couple of questions that came to mind that I thought were now out of context due to the reduction of imperial measurements, I was a little surprised that these were still part of core maths, yes perhaps learn them but not in exams.
The first was a question where the old measurements i.e. inches, feet, yard, chain, furlong & mile, the question stated how many inches in a foot, feet in a yard, yards in a furlong, furlongs in a mile etc. the actual question then was how many yards in a mile, she had no idea what most of those measurements were so I showed her that if there are 8 furlongs in a mile, 220 yards in a mile then there are 1,760 yards in a mile simple to me as I already knew the answer, but for a 14 year old perhaps a bit of a task, there was another giving a plan diagram of the front of a house, the roof had 45 Deg angles on the ends these all had measurements, the question was to find the area of the plan view,she was ok with the rectangles, but got stumped on the sloping roof, I showed her that effectively without any complicated maths just imagine them as a square (hence the 45 angle) then divide the area by 2, simple, I was amazed that the teacher marked them both wrong? When I challenged them at a parents evening the teacher was adamant they were wrong & even stated that they knew a mile was 1220 yards ? I also had the experience of taking a teachers onto site (my boss was chairman of the Parents/teachers at a school), the idea was to show them what goes on in industry, well I will not go on but those trips put me off teachers.

Sounds like you've encountered a teacher from the Ms Trunchbull teacher scheme. I'm big, you're small, I'm right, you're wrong.

parky said:

I was amazed that the teacher marked them both wrong? When I challenged them at a parents evening the teacher was adamant they were wrong & even stated that they knew a mile was 1220 yards ?

Click to expand...

I wouldn't even threat legal action... I would take them to court and call in a certain section of the UK media that longs for the empire to come back to report on it. The demand would be a formal apology to your daughter in front of the whole school as well as financial compensation if this was a paid establishment. Some people MUST suffer consequences for the protection of others in their path.

This reminds me of an electronics teacher in high school that decided to teach computers (DOS, more specifically)... I'd been lucky to have won a computer course a couple of years back (they had those back in the day) so would ace it. He discounted me on an answer about copying a file from folder to folder because I didn't include the C:> in the answer... I bottled it even after showing him that the command in the absolute form works everywhere and as such I didn't need to add the prompt to indicate from where the command was issued and he didn't budge. Today I'd have been marching to the school head asking for his head on a platter. He knew electronics, was actually a great teacher overall, but this event made me despise him. No one knows everything, we all make mistakes. How we deal with this is the important trait.

The school was slated by ofstead shortly afterwards, teachers were sacked (well removed), it then was turned into an academy (sort of thing that happens now, don't see how changing it's name helps). It's probably something I should have done but it appears others must have due to the ofstead action, my daughter did not have the grades to go into the 6th year but worked hard at colledge for a couple of years & managed to obtain the grades to get into university, she is now a qualified nurse, unfortunately by the time she got into uni, the NHS stopped the bursary course fees so it cost quite a bit for her tuition & accomodation, had the school been of the quality expected, it is possible she could have got the grades, the Uni course would have been funded by the NHS & her student loan would have been half.

That sucks for your daughter. I had a **** poor maths teacher at 6th grade that created a black hole in my maths knowledge until I reached the 11th grade and a teacher got so frustrated with his students not getting good grades over stuff that they should have learned that he booked a bunch of us to have separate lessons with him (free of charge and not paid by the school) and closed those gaps with us. I owe that man my career, but sadly he's the exception.

Yes I know what you mean, when I was at university, we had a tutor that would write on a blackboard while he was talking, we had to pen this in our notebooks, the idea was when we got home, we would take our scribbled notes & write it out properly, we all thought this was mad, it seemed to be difficult to listen what was being said & writing it down, never seen it used so aggressively before, however, this turned out to be a good way of putting it into long term memory, it worked for me just like he said it would, nearly 50 years on & I still remember it, still have my notes. probably the best tutor I have ever had.