I’m working on a school project and need some help figuring this out. The question is as follows.
When a momentary button is pressed it will cause two lights to toggle between each other. Ie press the button and release it once and light one is on, press and release the button again and light one turns off and light two turns on. Press and release the button again and light one turns back on and light two is off.
I can only use a momentary NO switch and as many relays as I need. And obviously two lights. I’m working with all 24vac components. Any help would be much appreciated.

 

There are quite a few schemes for alternate relay operation, and in addition there are relays made of exactly that function. This is a classic challenge exercise. often it is implemented with AND gates in solid state logic. That scheme can also be implemented with relays.

 

Welcome to AAC.

It’s hard to believe that you would get this assignment and yet have no material from either class or a textbook to point you in the right direction. That said, what would your first try at this look like? What do you imagine the relays could do to make this happen. Think about it, propose some solution—we can help guide you as you refine your understanding.

Although the answer is “trivial“ for those who have learned it, this is truly foundational knowledge. But puzzling it out mostly on your own you will gain a big advantage when facing more advanced topics which are often just complicated combinations of thing like this.

Good luck! Feel free to ask any questions related to your investigations of the answer, that are plenty of people ready to help.

 

Welcome to AAC.

It’s hard to believe that you would get this assignment and yet have no material from either class or a textbook to point you in the right direction. That said, what would your first try at this look like? What do you imagine the relays could do to make this happen. Think about it, propose some solution—we can help guide you as you refine your understanding.

Although the answer is “trivial“ for those who have learned it, this is truly foundational knowledge. But puzzling it out mostly on your own you will gain a big advantage when facing more advanced topics which are often just complicated combinations of thing like this.

Good luck! Feel free to ask any questions related to your investigations of the answer, that are plenty of people ready to help.

this is my like 30th attempt. I feel like it’s close but when I wire it up the relays chatter and won’t unlatch to reset R1 and R4.

 

hi D12345,
Do you have the contact closure and release times for the relay types you are using?
Usually stated on the relay datasheet.
E

Example.

 

hi D12345,
Do you have the contact closure and release times for the relay types you are using?
Usually stated on the relay datasheet.
E

Example.
View attachment 333287

I do not have that info. They are just ice cube relays.

 

Hi D12345,
Your relay chatter problem could be due to the operate/release delays of the relay contacts overlapping.??
Or a bouncing contact on your push button.

Do you have an oscilloscope on the bench, if Yes, you could measure these delays using one of the relays.

E

 

I have one for a dual relay toggle/Flip-Flop with one P.B.

 

I can only use a momentary NO switch and as many relays as I need. And obviously two lights. I’m working with all 24vac components. Any help would be much appreciated.

Are any other components allowed like resistors?

 

Are any other components allowed like resistors?

No other components allowed. Just two lights, a momentary NO switch, and any number of relays.

 

No other components allowed. Just two lights, a momentary NO switch, and any number of relays.

Are the relay contacts SPDT only?

 

Are the relay contacts SPDT only?

No. Relays can be DPDT.

 

... or 3PDT... or 4PDT.... etc.

didn't wire it to test it out but something like this should work. it uses just three relays.... or 2 relays if button has sufficient number of contacts (K1 could be eliminated)
the first lamp can be connected in parallel with K3 but ... for large loads, this would require other relays to be larger too... by connecting loads only to K3 contacts, relays K1 and K2 can be smaller.

 

didn't wire it to test it out but something like this should work. it uses just three relays.... or 2 relays if button has sufficient number of contacts (K1 could be eliminated)

I don't know for sure if that follows the pattern described from post #1.
The TS says: "press the button and release it once and light one is on, press and release the button again and light one turns off and light two turns on. Press and release the button again and light one turns back on and light two is off".
It doesn't mention a light being ON when power is applied.

 

easy fix... add one more relay that "enables" lights. it should be latched (and remain latched) when button is pressed.

 

something like this

 

and here is simulated version
https://app.plcsimulator.online/YXeRcf63iXFQJtovDFVa

click on Play button (upper right corner)
observe Lamps 1 and 2.
keep clicking on PB contact to simulate press....

 

and here is simulated version

Will that actually work in the real world as the relay contacts take time when opening and closing.
Seems like there would be chattering.

 

Will that actually work in the real world as the relay contacts take time when opening and closing.
Seems like there would be chattering.

Unfortunately that’s what happens. Relay 3 won’t stay latched when button is released.

 

Wow - ladder logic. I struggle with that.

Here's a sequencer that steps a light string in a loop. If it is shortened to just two lights I think it performs as requested. It's drawn from memory so no promises, but basically it uses the first relay to turn the PB into a SPDT which has two states - pressed or unpressed, and these two states are used to step along sets of two relays, one to catch and one to carry.

I think I derived it from part of an IBM calculating accounting machine (maybe a 419?? long time ago).

Any criticism appreciated.

Turning it into ladder logic is left as an exercise for the reader.