DPDT latching relay substitute

Thread Starter

Noisettes

Joined Oct 7, 2017
17
Hi, wondering if this is feasible...
Im trying to substitute the dpdt latching relay in the bottom right with a jk flipflop because dpdt relays arent available here and a flipflop was the first latch i could think of.

Screenshot_2017-10-08-01-22-36.png
The circuit is a keypad password circuit that opens the connection in the dpdt relay, the output of the password(AND gates) goes to the 555 timer which then makes the dpdt flip and latch.

If anyone has better ideas im open to it
Thanks
 

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dl324

Joined Mar 30, 2015
13,815
Im trying to substitute the dpdt latching relay in the bottom right with a jk flipflop because dpdt relays arent available here and a flipflop was the first latch i could think of.
Didn't bother trying to analyze the circuit because it looks like it was drawn by a newbie.

There is no substitute for a latching relay. A latching relay will stay in the desired state without having a coil energized constantly. No amount of logic around a non latching relay will emulate that functionality.
 

crutschow

Joined Mar 14, 2008
28,474
You could substitute an RS latch (or the set/reset inputs of a flip-flop) for the latch relay but it will require that power be continuously applied to remember its state.
 

Thread Starter

Noisettes

Joined Oct 7, 2017
17
Continuous power is fine, ive replaced the battery with a power adapter.

Ah, i forgot to mention, im using the flipflop to power an spdt relay instead. The flipflop will latch(set) allowing the coil of the spdt to run.
 

crutschow

Joined Mar 14, 2008
28,474
Continuous power is fine, ive replaced the battery with a power adapter.

Ah, i forgot to mention, im using the flipflop to power an spdt relay instead. The flipflop will latch(set) allowing the coil of the spdt to run.
You will need to add a transistor buffer at the output of the FF to drive the relay coil.
Don't forget the transient suppression diode (1N4148 or similar) across the relay coil (cathode to plus).
 

Thread Starter

Noisettes

Joined Oct 7, 2017
17
You will need to add a transistor buffer at the output of the FF to drive the relay coil.
Don't forget the transient suppression diode (1N4148 or similar) across the relay coil (cathode to plus).
Thanks :) definitely learning a lot here. Appreciate all the responses also

(But this is the same circuit as my AND gate problem..so if i cant get the AND gates to work then i cant connect their output to the flipflop)
 

Alec_t

Joined Sep 17, 2013
12,444
Do you really need a relay, or would a transistor (BJT or MOSFET) switch do instead?
Can you source CD4000 series ICs?
 

Thread Starter

Noisettes

Joined Oct 7, 2017
17
Philippines...part im at doesnt have any HC...only LS
In fact, this project probably wouldve been finished already if not for the part availability OTL

(online shipping..hurts..plus cant buy just one part...also budget concerns...so...)

..a transistor switch...never thought about it. Would it make more sense? I just need to close the connection between an electric lock to its battery...in essence making a complicated toggle switch i guess
 
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