Make a latch (flip-flop) using two relays?

[mank]

Had an interview today. There was a test. They wanted me to draw a diagram and this was what I was supposed to do:

"Draw a latch (flip-flop) using two relays. Show inputs and outputs"

I have never seen relays used in this way. I have been a Navy Electronics Technician and in the field for over 30 years.

I just could not figure out how to do the 'toggle'.

Anyone got any ideas?

 

[(*steve*)]

Perhaps we should wait a few days, just in case...

Here's some hints.

1) can I wire a relay so that once power is applied, it latches on?
2) how could I, with another relay closing, reset this?
3) can I interconnect 2 of these together?

I've never considered this either. I think the test was not so much about the flip-flop as how you think on your feet.

I've posed questions of this nature to potential job applicants before. I was more interested in how they approached an unfamiliar problem, than how they solved it.

 

[Laplace]

Check out these sites:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1338590/
http://tams-www.informatik.uni-hamburg.de/applets/hades/webdemos/05-switched/20-relays/flipflop.html

 

[(*steve*)]

But you can do it with just relays and switches.

 

[baileya]

flip flop using two relays

To answer the question on the flip flop using two relays, it can be done utilizing two timers , one timer to switch between the relays and the other timer to reset the circuit
Start with one relay instantly energised , then timed off. Next switch on the other relay and provide a hold contact . The second timer is used to stop and reset the circuit allowing it to start the cycle all over again.
I can draw out a circuit wiring diagram but not sure how to post the circuit on this site
Cheers
Arthur

 

[Osmium]

A lot of years ago, I made a flip-flop using two relays and two switches. I think I also had a light globe to show the state! Just like Steve says, think about it...

--- Warning: Nostalgia piece...
The school radio club used to get a lot of surplus telephone switching gear and other bits and pieces. Full of relays and all sorts. Kept us happy for ages! [btw our surplus gear was well and truly valve era. My first transistors to play with were OC45s and OC71s - and expensive!!]

-Roy

 

[Lee Ssang]

Had an interview today. There was a test. They wanted me to draw a diagram and this was what I was supposed to do:

"Draw a latch (flip-flop) using two relays. Show inputs and outputs"

I have never seen relays used in this way. I have been a Navy Electronics Technician and in the field for over 30 years.

I just could not figure out how to do the 'toggle'.

Anyone got any ideas?

I think this link may answer your question:

http://yamanashimasamune.blogspot.my/2016/04/flip-flop-or-bistable-latching-using.html

 

[Colin Mitchell]

Look at this brilliant example:


You short across the supply to turn the circuit off !!!!!