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Flip flop

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keinw

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Hello,
I am looking for the simple way of doing impulse switching. One impulse must switch on power (220Vac, 1A) and another must switch it off. One push button will be used.
At first I thought I need a latching relay, but it turned out to be not suitable as 1 coil latching relay requires to switch polarity for it to switch and 2 coils latching relay requires two buttons.
Then I looked for small two steps relay, but I could not find anything like that.

I think that I need some kind of simple IC which would decode impulses into high/low state of one output and use a simple power relay. The question is, what IC will do the job? I would also prefer it to have a memory (when power goes on, output switches to its last state). I have found NTE754, but its datasheet does not specify whether it has memory or not, and - what is the most important - it is very hard to get one where I live.

Please do not offer to use PICs or anything like that - it is not a simple way of handling my problem.
 
If you can find a T or JK flip flop IC, that would probably work for you; you would also need to set up a debounce on the button input, then the output of the flipflop would go to your relay (via an NPN or N-channel FET)...I think that would work...
 
For the debauncing I will use a small electrolytic capacitor. I found some <= 10 mA relays, so I hope that I won't even need FET or transistor.
The problem is - I do not know what flip flop IC should I use.
 
If you want memory then you will need to add an independent power source to keep the flip-flop energized. A CMOS FF such as the 4013 should work. You connect the "D" input the the /Q input, and the de-bounced switch signal to the clock input. (Ground all unused inputs). Make sure you put a diode across the relay coil (cathode to positive) to suppress the coil transient.

To maintain the FF memory you could power it from a battery. CMOS uses essentially no current when in a static state, so any battery should last about as long as its shelf life. For alkaline or lithium batteries, or button cells, that would be many years. You would need a different source to power the relay, since it takes significant current.
 
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