Safe Speed Forums

You have five two-way switches (SPDT), two lamps and a battery.
Wire them up so that:
Lamp 1 is on if, and only if, all five switches are up, and,
Lamp 2 is on if, and only if, all five switches are down
You're not allowed to short-circuit the lamps or the battery.

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

What nomenclature do we use for the relays and terminals?

Ah, never mind, I'm scribbling on paper. It's just a question of who gets there first.

My money is on Steve or Botach but it depends who is watching, so it's unfair really

Off the top of my head, the number of relays is irrelevant here, you tinker...

PS. I think I need to take a picture of my drawing and post it here via Photobucket

Are the relays from RS, Farnell, DigiKey or Maplin?

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The views expressed in this post are personal opinions and do not necessarily represent the views of Safe Speed.
You will be branded a threat to society by going over a speed limit where it is safe to do so, and suffer the consequences of your actions in a way criminals do not, more so than someone who is a real threat to our society.

Who said anything about relays?

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

No need to post your solutions, you'll know when you solve it.

For the record, it took me all of about 10 minutes to solve - there were others in my group who, to my knowledge, still haven't solved it several decades later

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

Sorry, I meant switches but I was thinking of relays because I just used one to hook a second 120db horn on my motorbike

Apologies. My paper wot I wrote on shows switches, not relays - honestly.


Silly Tone

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The views expressed in this post are personal opinions and do not necessarily represent the views of Safe Speed.
You will be branded a threat to society by going over a speed limit where it is safe to do so, and suffer the consequences of your actions in a way criminals do not, more so than someone who is a real threat to our society.

Is that a 120dB silly tone?

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

..or a silly tone implant?

..silly tone boob?

..now this is getting silly, Tone

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

Cut me some slack Pete.

Yes, 120 megabells or something

I'm going to stick my 50 ohm head in a book now. That's Green, Black, Black, and I'll go for gold on the last one, (from the old days), because I'm worth it

_________________
The views expressed in this post are personal opinions and do not necessarily represent the views of Safe Speed.
You will be branded a threat to society by going over a speed limit where it is safe to do so, and suffer the consequences of your actions in a way criminals do not, more so than someone who is a real threat to our society.

I always thought in that context dB was relative to something .( As in transmission of sound ,3dBm etc).An attenuator can be 3dB (AND TO BE PEDANTIC A -3dB attenuator is an amplifier).
Resistor wise -I'm a bit out or touch ,but don't we have another couple of bands on a resistor nowadays .

Bit back to the problem -think AND gates Tone and all becomes clear .

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lets bring sanity back to speed limits.
Drivers are like donkeys -they respond best to a carrot, not a stick .Road safety experts are like Asses - best kept covered up ,or sat on

I thought about it for about 10 minutes (with some scribbling on bits of paper), got distracted for a while (you'll soon know why, keep an eye on the 150mph biker thread); revisited the problem and got it straight away. My solution is surprisingly straightforward (well, I think it fits the criteria - just).

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

I would suggest solution is very simple -as i said -think "AND" gates(which a SPDT switch is)

IMHO-it's more of a question of solving the logic ,and transposing it into a circuit drawing .For the sparkies - who'll know two way light switches well - you don't need to grasp the logics -just expand two switches to five and add the lamps at the end .( Or have I given too much away ,Pete).

_________________
lets bring sanity back to speed limits.
Drivers are like donkeys -they respond best to a carrot, not a stick .Road safety experts are like Asses - best kept covered up ,or sat on

I've spent over forty years earning my crust by solving this kind of problem and I can't get this - even into the second bottle of wine. In fact I would happily write a paper showing why there is no solution - you can't create two independent and gates without having two independent sets of switching elements. And the solution hinted at by Botach (exclusive or gates), which was the first thing I turned to, seems to satisfy the "if" but not the "only if" criteria of the problem. So if you will put me out of my misery I will turn my certificates face to the wall, hang up my soldering iron, and grovel for a full 50mS. I will even sign travis's petition about the firmware of the 20-20 laser.

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When I see an adult on a bicycle, I do not despair for the future of the human race. H.G. Wells
When I see a youth in a motor car I do d.c.brown

I can assure you that there is a solution, and there's no trickery involved.

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

It appears my solution was wrong, or at least wasn't the desired answer Well, my solution was a bit too simple (even simpler than yours Botach)

Pete,

Can the solution ever be allowed to present a short circuit (to the battery) for any other combination of switch positions?
Is it OK to short a lamp if there is no voltage across it?

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

And the solution really meets the criteria if and only if five switches are in the same position?

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When I see an adult on a bicycle, I do not despair for the future of the human race. H.G. Wells
When I see a youth in a motor car I do d.c.brown

No



Yes

As I said, no trickery, no hidden extras, just wiring it up correctly

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

I got that one pretty quickly too. Lamps in series between pos and neg. Junction of lamps connected to all switch wipers. Normally open of all switches to pos. Normally closed of all switches to neg. But that is an engineering nonsense.

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When I see an adult on a bicycle, I do not despair for the future of the human race. H.G. Wells
When I see a youth in a motor car I do d.c.brown

I'll make it a bit easier - the one side of both lamps are connected to the one side of the battery.

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

I SAID
"IT'S A QUESTION OF "AND "GATES ,and later , an expansion of the two way light switch .


It's really a simple solution .A SPDT has two states .Add them on series( with a twist,and that's the hint), and think of linking the return to the battery from the lamps as a common feed(AS PETE SAID) .Sorry ,Gents - I cheated ,and drew on my past ten years of rail signalling experience - where all things in front of train need to satisfy conditions ,and added my background in logic . I'm working on getting my solution done in EXPRESSPCB to a picture for photobucket .

_________________
lets bring sanity back to speed limits.
Drivers are like donkeys -they respond best to a carrot, not a stick .Road safety experts are like Asses - best kept covered up ,or sat on

Is the number of switches significant?

_________________
When I see an adult on a bicycle, I do not despair for the future of the human race. H.G. Wells
When I see a youth in a motor car I do d.c.brown