The alternative is to use double pole relays. Then the diodes are not required for isolation.

You keep saying you can do a relay circuit without diodes.
Please show us how it's done.

 

Diodes.

Mr Bill is correct in that the relay coils need to be moved to the top side of the LEDs, but that's not all..You need to add what are called steering diodes to prevent cross-connections. The way you have it now, pressing any button activates all relays including the one for the LED you want on. You get a very brief blink out of the LED, then nothing until you release the button and press another.

Steering diodes (2 per relay) prevent this. I'll try to whip up a schematic. It will look a bit more complex, but the logic is exactly the same as you intend.

And you do need spike suppression diodes.

And two relay coils will kill a 9 V battery pretty quickly.

Are the switches momentary? Will there ever be a time when two are activated at the same time?

ak

Thanks Analogkid and Mr. Bill. Will move up those connections. Now you pointed out that all 3 relays will indeed receive current flow, that was one of the reasons I abandoned it. Forgot that - been at this too long. However the steering diodes sound great - never heard of them but will look into it. I have changed my design - only 2 lights/switches/relays will be involved. Yes both could be triggered simultaneously but very rare they would be EXACTLY the same time. It would be like trying to trigger 2 push buttons at EXACTLY the same moment one with each hand. At the speed of current flow I was not sure it could happen or what the result would be. I also heard about back spike in relays which sounded like a challenge. I think I will have to study up on one of the solid state solutions. Speed and small size are important.
Thanks
Brewster

 

Still don't see it.

ak

Thanks MisterBill2. Can you elaborate a little? Not visualizing how double pole obviates the steering diodes you guys mentioned.
Brewster

 

I think I will have to study up on one of the solid state solutions.

Just ask questions here, and we'll help with the learning process.
If you can solder small connections, it shouldn't be a problem.

 

The TS says the first switch activated will stay closed and then should ignore any subsequent switch closures.
I don't think it's defined as to what a radio button circuit does if one switch stays closed and then a second switch is closed.

The concept is after the first switch closes illuminating its LED the cycle is finished. Rest the switch and start over. A bit like bowling - get a strike and you don't throw a 2nd ball. Pins are reset.

 

Which to me is a radio button circuit… but what do I know.

Here I go again - not familiar with radio button circuit.
Brewster

 

I have been thinking about this and if I understand the requirements my solution requires 3 DPDT switches, three 3PDT relays, 1 SPDT relay and three LEDs, of course.

Basically each switch has an associated relay and LED. The V+ bus that is used by to actuate the relays is shared, and the low rail is wired in series through the NC contacts of all three relays so that if any one fo them is actuated V- is interrupted making it impossible for any switch to operate its relay.

Each relay's coil is wired to V+ though its respective switch's NO contact.

Each associated LED is wired to its respective relay's NO contact.

The SPDT (reset) relay coil is wired through each relay's NO contact the NC contact on the operating relay's switch with the switch's common connected to V+, and the V+ of the coil bus is wired to its NC contact.

The initial condition allows any switch to send power to its relay's coil. When it does, four things happen.

1. The shared V- of the coil bus is interrupted.
2. The particular relay is connected to a separate V- of the coil bus not wired though the relays
3. The NC contact of the relay's operating switch is connected to the time delay relay to provide V+ to its coil
4. The LED is connected to V+

In this state the energized relay is latched through its own contacts. The V- of the coil bus is interrupted so operating either of the other two switches will have no effect. The LED is lit.

The reset occurs when the operating switch of the latched relay is set to the off position.

When this happens, the reset relay is energized interrupting the main V+ rail and causing all both the latched relay and itself to de-energize. This restores things to the initial condition, disconnecting the NC contact of the operating switch from the reset relay's coil.

It might be necessary to use capacitors to power the latched relay actuated for enough time after it has disconnected the V- of the coil bus, including its own, to actuate and connect itself to the alternative V-

Of course there are various resistors and diodes not mentioned, just assume they belong there.

 

Of course there are various resistors and diodes not mentioned, just assume they belong there.

(My diodes are flyback, not directing.)

 

OK, here is the description using 3 double pole relays, each having two normally closed contacts. Each relay coil is connected to the circuit between the switch and the light, so if SW1 closes then relay #1 operates, removing the power feed to lights #2 and #3. If realy #2 operates, the two contacts open the power feeds to lights #1 and #3 So there are two normally closed relay contacts in series with each power feed. SW#1 has contacts of relays #2 and #3 in series, SW#2 has contacts of Relays #1 and #3 in series with the power feed, and SW#3 has contacts of Relays #1 and #2 in series with it's feed. I can't see it except in my mind, but that is what it looks like and how it works.
AND, if the LED were fed from the NO contact on each relay, then it will be isolated from any inductive spikes that might appear. A small bit more compexity, but no diodes required.

 

You keep making contradictory statements. That is confusing those trying to help.
Are there two lights or three lights? Are the switches toggle switches or momentary pushbuttons?
What is supposed to happen when one switch is on? honk a horn? Kick the dog? Ring a bell? what?

You can probably do what you want with just toggle switches...

I hope I am replying to eetech00. The only change I believe I made, after getting way more helpful feedback than anticipated, was going from 3 lamps to 2. The rest is the same. My original question included a close solution (YouTube) using switches and wires alone. I could not find a configuration to keep the 1st light on and prevent the others form getting power. As I explained in one response some of the problems you are all mentioning with relays I had read about but didn't really understand. The recent mention of steering diodes could help and how to prevent back spikes. The switches would be normally open but temporarily closed while pressed - momentary if that is the term. I can shop the switches. That was not my problem. For your question about result, the illumination of the LED is the ONLY result. That's it! I just don't want more than one on.

Seems like I am upsetting too many people here. I am overwhelmed with replies. Perhaps I should study up on your solutions you already offered and shut this down.

Brewster

 

here is the description using 3 double pole relays

I would think that you would know that the mantra on this website is, schematics are the language of electronics, (or a picture is worth a thousand words), or do you not have the capability of drawing a schematic?

 

OK, here is the description using 3 double pole relays, each having two normally closed contacts. Each relay coil is connected to the circuit between the switch and the light, so if SW1 closes then relay #1 operates, removing the power feed to lights #2 and #3. If realy #2 operates, the two contacts open the power feeds to lights #1 and #3 So there are two normally closed relay contacts in series with each power feed. SW#1 has contacts of relays #2 and #3 in series, SW#2 has contacts of Relays #1 and #3 in series with the power feed, and SW#3 has contacts of Relays #1 and #2 in series with it's feed. I can't see it except in my mind, but that is what it looks like and how it works.
AND, if the LED were fed from the NO contact on each relay, then it will be isolated from any inductive spikes that might appear. A small bit more compexity, but no diodes required.

Thanks so much MisterBill2
Brewster

 

OK, here is the description

And now, a word from Rear Admiral Joshua Painter:

"Engineers don't take a dump, son, without a schematic."

ak

 

@ Mr Crutschow. NO, I do not have the means to produce any drawings that I can post.
I really pity those folks unable to visualize or even sketch from a detailed description.
Consider that most wire-wrapping and circuit boards are described by connection lists, which are rather more terse forms of detailed descriptions.
Likewise, many electrical connection drawings are graphic versions of detailed descriptions. AND CNC programs are detailed descriptions of what it takes to produce an object, although in a very different language.
Visualizing from a description is a valuable skill indeed.

 

I really pity those folks unable to visualize or even sketch from a detailed description.

I sure as heck don't need your pity or condescending attitude.
Sorry I'm apparently not as good at visualizing as you, but it's not at the pity level.

NO, I do not have the means to produce any drawings that I can post.

Really.
So, you don't have access to a computer?

 

It turns out that I am spectacularly good at visualizing, and after a bit I decided to slog through an unappealing paragraph.

Wally, each switch is not steering currents to the other two relay coils as the TS did. Each relay's poles are in series with the other two switches.

ak

 

Wally, each switch is not steering currents to the other two relay coils as the TS did. Each relay's poles are in series with the other two switches.

OK. Thanks for the update.
I'd have to draw it to visualize it, but I'm not motivated to do that.

 

Seems like I am upsetting too many people here. I am overwhelmed with replies. Perhaps I should study up on your solutions you already offered and shut this down.

I would not say that you are upsetting too many people. Around here we're all big fans of clearly stated goals and design criteria, which this thread lacked, but that doesn't account for the bag of pissed off kitties that this thread turned into. I don't know what is going on here; I feel like I missed something. Tensions are apparently high, and you may have had the misfortune of being in the wrong place at the wrong time.

 

A similar function is used in the mechanical "winner" detection system for Cub Scout ""Pinewood DErby" race cars. The first to cross the finish line is the winner. I designed a circuit, using relays, for a four lane track about 30 years ago. It used multiple contact relays and 24 volt light bulbs. I don't recall any details except that it worked.

Sounds like a perfect example. Thanks

IF you would tell use what you actually want to do it would be very helpful. Your "simplified" case makes things much harder for those trying to help you. Each time you add a little information it changes things more than you expect because you don't know what information is important—or you wouldn't ne asking for help.

It would also help if you would try being a little flexible and not insist the solution be scaled to your ignorance. Transistors, ICs, and other devices are a much better solution in almost every case and if you allow us to explain how to use them you might find it very straghtforward after a bit of confusion at the beginning.

Yikes! "Scaled to my ignorance." Actually that was well said and you are correct. I am asking experts to "dumb down" a solution for an amateur which is not appropriate for this forum. I am out of my league and do not expect a beginner's tutorial. I am sorry if I wasted some of your time(s). I think I will take what all of you have offered and go back to the library to bone up on basic electronics. My electrical knowledge is high school level from the '60s. Transistor radios were the latest invention. To answer the many curious here is the best analogy I can muster - can't give specifics if this is ever commercialized. Let's assume you want to analyze your tennis stroke. Is your racket leaning forward (topspin), back (backspin), or perpendicular? You swing on front of a device - probably with lasers or a beam rather then a mechanical switch, and swing. If the top of the racket breaks its beam first, one light illuminates - not the 2nd. If the bottom is first, a the other one illuminates, not the top. That's it- end of cycle - the only feedback you receive! Naturally the other side of the racket WILL break its own beam but it is too late. You get one or the other. Same could be for a golf club - toe first or heel first, but this one would require super speed.

Hope this clarifies it but I have so many responses now I am not sure I can keep track. The forum is more complex than the circuit!

Brewster

 

Let's assume you want to analyze your tennis stroke. Is your racket leaning forward (topspin), back (backspin), or perpendicular? You swing on front of a device - probably with lasers or a beam rather then a mechanical switch, and swing. If the top of the racket breaks its beam first, one light illuminates - not the 2nd. If the bottom is first, a the other one illuminates, not the top. That's it- end of cycle - the only feedback you receive! Naturally the other side of the racket WILL break its own beam but it is too late. You get one or the other. Same could be for a golf club - toe first or heel first, but this one would require super speed.

This is probably the best information you've provided in the whole 80 post message thread.
You can probably just use toggle switches and relays (maybe not relays).

However, what did you mean to say here?:

"If the bottom is first, a the other one illuminates, not the top. "