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

mank

Apr 14, 2011
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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*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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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.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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But you can do it with just relays and switches.
 

baileya

Jan 31, 2013
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Jan 31, 2013
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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

Jan 28, 2013
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Jan 28, 2013
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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

Apr 18, 2016
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Apr 18, 2016
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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

Aug 31, 2014
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Look at this brilliant example:

Toggle.gif
You short across the supply to turn the circuit off !!!!!
 
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