Brain teasers

Karlos_Sparky

Ok all thought this was worth a trial as a sticky.
Remember you can always just post that you know the answer and give others time to work it out.



HELP NEEDED !!!!

I'm in electrical phase 2 in Ballyfermot and as we were leaving our instructor (Pat) gave us this as a brain teaser . My Head is wrecked and I can't wait till tomorrow for the answer !! There are 3 lamps wired in series in a circuit and we have to change the circuit to parallel using only a double pole switch.

I made a very crude drawing (attached) .... Any ideas ???


Many thanks

Andrea B.

My head is wrecked now as I see numerous ways of doing it even without DP switch. What were his criteria/limitations? Are we allowed disconnect and reconnect?

Karlos_Sparky

I'm not too sure - I don't think much has to be done at least thats the impression he gave .... I will post the solution tomorrow .... My brain is mush

Steve

easy peasy.....:D

staker

will i PM it to you OP?

Steve

Here ya go - took me a minute to draw it.

dingding

SteveC wrote: »

easy peasy.....:D

By 2.....

Our posts overlapped, yours is a better drawing, mine is very crude.

staker

Nice DP sqwitch!!:D

Andrea B.

?

Andrea B.

Here ya go - took me a minute to draw it.

Too inverted and you've a one-way switch left over;)

staker

Throw away the shovel...:cool:

Steve

dingding wrote: »

By 2.....

Our posts overlapped, yours is a better drawing, mine is very crude.

We both got it - equal cred. I just happen to have a cad system at home:p

Andrea B. wrote: »

Too inverted and you've a one-way switch left over;)

orly? the OP never said it had to be used...;)

Andrea B.

We both got it - equal cred

Ehemm.

dingding

Thanks,

All I had was MS Paint.

Anyone got anymore teasers while I am in the mood.

Andrea B.

Anyone got anymore teasers while I am in the mood.

You have just moved into an old house with a basement and an attic. There are three switches in the attic, marked "on" and "off". The three switches are connected to three bulbs in the basement.

You have to find out which switch is connected to which bulb. You are allowed to play with the switches for as long as you need to, but you may only go down into the basement once to check the bulbs and then say which which switch is connected to which bulb.

Steve

Andrea B. wrote: »

Ehemm.

Sorry, credit where it's due - 3 way split?..:D

Andrea B. wrote: »

You have just moved into an old house with a basement and an attic. There are three switches in the attic, marked "on" and "off". The three switches are connected to three bulbs in the basement.

You have to find out which switch is connected to which bulb. You are allowed to play with the switches for as long as you need to, but you may only go down into the basement once to check the bulbs and then say which which switch is connected to which bulb.

easy peasy - I won't spoil it yet though...

dingding

Turn Switch 1 on for 5 minutes and switch it off
Turn Switch 2 on
Leave Switch 3 in the off position.

Go down to the basement.
























Switch 1 = warm bulb that is off
Switch 2 = bulb that is lit
Switch 3 = cold bulb that is off

:D

dingding

Andrea B. wrote: »

Ehemm.

Agreed, 3 Way split

Andrea B.

Sorry, credit where it's due - 3 way split?..

We'll see. "Pat the instructor" might leave us all standing!

dingding

Wonder if "Pat the instructor" has any other good teasers.

dingding

Here is another one?

You have to (two way) switch the light on in the corridor from both rooms.

You can not add any more cables to the lamp. (i.e. you can't get any more wires through the wall) You have access to a live and neutral in each room and any switches you like to purchase.

Solutions please

DublinDilbert

dingding wrote: »

Here is another one?

You have to (two way) switch the light on in the corridor from both rooms.

You can not add any more cables to the lamp. (i.e. you can't get any more wires through the wall) You have access to a live and neutral in each room and any switches you like to purchase.

Solutions please

Ahh that's too easy...

dingding

Well Done !

watty

Wire lights on ground, 1st, 2nd and top floor halls.

Thus Four lights.

Switch them all on or off with a single switch at any of the 4 places

Hint: The light switchs are all standard domestic types.

watty

Advanced exercise.

A push button switch on each floor and lights go off on their own.

Three Solutions (describe the 1st two):
1) Relay and one simple component.

2) 555 IC, 12V DC supply and Relay.

3) Dedicated Electromechical Timer Module. Too easy.

Why is (2) more flexible?

Steve

watty wrote: »

Wire lights on ground, 1st, 2nd and top floor halls.

Thus Four lights.

Switch them all on or off with a single switch at any of the 4 places

Hint: The light switchs are all standard domestic types.

crossover switches?
standard domestic but rare IMO.

Steve

watty wrote: »

Advanced exercise.

A push button switch on each floor and lights go off on their own.

Three Solutions (describe the 1st two):
1) Relay and one simple component.

2) 555 IC, 12V DC supply and Relay.

3) Dedicated Electromechical Timer Module. Too easy.

Why is (2) more flexible?

1) I'm intrigued by this, can't figure it.
2) yes, more flexible but not reliable without a lot of background electronics.
3) electropneumatic switches are the norm for this application.

My solution would be a simple push-button on each floor wired in parallel to a delay-off timer with the lights switched via a consumer-unit type 1-mod contactor.

watty

1) Large PTC thermistor and 2-pole relay.

One pole connects relay coil to supply via the PTC. When it heats up the current is too low and relay opens diconnecting it (otherwise when it cooled it would connect again). The PTC is chosen based on time and Relay coil current. You may need a parallel resistance/lamp across the relay coil to draw enough current or change delay.

Momentary switchs to power relay all in parallel.

The other relay pole operates the lights. Can use 220V AC relay coil.


(2) can use Cat3 or Cat5 wiring and allow easy adjustment of delay. Very reliable, 3 capacitors, 3 resistors, one transistor/FET one 12V relay. Low cost. Google 555 timer. Can be used with very cheap "alarm circuit type" movement sensors that can't drive solution (1) or (3) directly. Mains switching sensors cost more and need mains wiring. The low voltage movement sensors can use alarm wire, cat3 or Cat5.

Stoner

Great info guys

Is an aptly named sticky thread on the topic an idea? not that I'm a big sticky fan, but one for this might be fun, get the brain running.

dingding

SteveC wrote: »

crossover switches?
standard domestic but rare IMO.

My Solution also, Watty is this the answer you were looking for?

Steve

Stoner wrote: »

Great info guys

Is an aptly named sticky thread on the topic an idea? not that I'm a big sticky fan, but one for this might be fun, get the brain running.

Good idea - I'm enjoying these...:D

dingding

SteveC wrote: »

Good idea - I'm enjoying these...:D

+ 1

watty

SteveC wrote: »

crossover switches?
standard domestic but rare IMO.

yes.

you can have as many as you like inserted on the two wires between the normal 2 way switches.

PWR --<====x=====x====x====>----0----Neutral

5 switches. Any switch will turn light --0-- on or off

hall to kitchen and upstairs.

Have a switch at kitchen door end of hall, one at front door(X over) and one upstairs. Very under used.

But then we have builders that think one double socket per room is enough. The problem isn't the poor Sparky but mean developers. Then people end up with extension leads and 4 way or 6 way socket strips everywhere and a gazillion adaptors. It's one thing to wire extra sockets when you are building a house but VERY expensive to add them flush with no visible trunking afterward.

A VIRTUAL Beverage of your choice to all who spotted how simple it is.

DublinDilbert

watty wrote: »

But then we have builders that think one double socket per room is enough.

This indeed is a major problem... in fact a house can be certified even if there's only one socket in it, once that socket is required correctly...

In places like the US/Canada the building regulations will require you to have a double socket every x number of feet on each wall!! this is to prevent people using extensions / plug boards....

Karlos_Sparky

Sorry about the delay in getting back - it was perfect ...... and the 1 way switch had to be kept but it was just in the circuit as a master off ........

I will ask for a few more of these brainteasers ....

watty

DublinDilbert wrote: »

Ahh that's too easy...

But is it safe or Legal?

What if it's an ES fitting? Very common on PAR/Spot bulbs. Though I have a set of 3 spots with BC fitting and very few places stock the bulbs, most only have ES version.

dingding

Sorry for confusing, It was meant as an electrical circuit brain teaser not as meeting electrical regulations, I should perhaps have modified the question to say it the solution does not comply with electrial recs.

More puzzles please

watty

I learnt my wiring skills in UK, so I'm not always sure, e.g. in UK you must not (In my time) bond neutral to earth and here the neutral must be bonded to earth rod. That's a pretty major difference!

The fuse boxes used to be generally different. The circular screw in fuse not in UK.

dingding

watty wrote: »

I learnt my wiring skills in UK, so I'm not always sure, e.g. in UK you must not (In my time) bond neutral to earth and here the neutral must be bonded to earth rod. That's a pretty major difference!

The fuse boxes used to be generally different. The circular screw in fuse not in UK.

I think the older UK fuseboards had rewireable fuses. The Irish system if installed correctly with gague rings is probably safer.

Stoner

Remember you can always just post that you know the answer and give others time to work it out.

Steve

Good call Stoner. This could be a bit of craic..:D

Mr Magnolia

Right.

3 gang light switch in the hall. One of the switches controls a light in a room not visible from the hall. The other switches are unused. How do you figure out which switch controls the light?

Rules:

You can do what you want with the switch positions before you leave the hall.
You have only one opportunity to go from the hall to the room.
You have no way of seeing if the bulb is on or off before going into the room
You can't open the light switch.



x1.
x2.
x3.

______________________________________/ Door _______

-o (light bulb)








I may be omitting other rules, this will become evident...

Stoner

Ok Mr. Mag i think I have this one, we need some other element to use as part of the process and i think i have it now, I'll pm you the answer

Michael Collins

Ok I can't wait any longer, I have to show off!

I'd do it like so:

Turn Switch 1 On
Turn Switch 2 On for a few mniutes and then off again
Leave Switch 3 untouched

Now go into the other room and check:

If the light is on, it's Switch 1 that controls it.
If it's off and warm, it's switch 2.
If it's off and cold, it's switch 3.

This assumes that a) you know when a switch is on or off and b) the bulb is working and procduces a reasonable amount of heat! Not sure if it'd work with some LED lights...

It's just a small variation on the problem that we had earlier with the three lights.

Stoner

yep, the other element to add was heat, that's a great one lads, well worked out Michael Collins

brightspark

Here's an alternative answer to dingding's earlier post


http://www.mkelectric.co.uk/news/news.asp?newsid=1055

he did allow "any switches you like to purchase":D

brightspark

Here's a teaser for you

You just called round to a friend's house and he tells you he thinks the fuse in a plug top is blown, but you only have a simple phase tester in your pocket.

You know the socket is ok as you were able to test it with another appliance.

How can you check if the fuse has blown?

Steve

I actually had to think about that one brightspark.. good question.

Would you would stick the fuse on the user end of the phase tester and your finger on the end of the fuse?

Stoner

use the phase tester to open the plug on the other appliance and change the fuses over, if the previously tested appliance works then the fuse is fine, if not then it wont.

Might not be the most inventive option, but it's what I would do