NEED HELP LATCHING ASAP PLEASE!

[riceboy89]

proteus latching relay

PLEASE NOTE: I AM NEW SO I HOPE I POSTED THIS THREAD IN THE APPROPRIATE AREA!

Well i am designing a car alarm for a school project and i am running into problems latching the circuit. The alarm is using RF technology. On my transmitter, i send a high signal to the reciever to arm the alarm system. The problem i am running into is that once the button on the transmitter is not depressed, there is no longer a high signal, thus disarming the system. I have tried using a JK flip flop latching circuit clocked by a 555 timer, but that didnt work. Is there something easier to use such as a latching relay? I am including a schematic of my progress so far.

**broken link removed**

 

[leonzam]

latching relay proteus

you can use a JK flip flop (like the 74ls76)

connect j ank K to !Q and the input signal to clk

then everytime you receive a transition from low to high (on clk) the flip flop will be latched

now you can reset the circuit using the clr pin

Added after 3 minutes:

ups !!! my mistake
the transition is from high to low ( the clk pin is inverted)

 

[docel]

You can also use an SCR for latching the O/P. But you need to manually Reset the latch.

 

[riceboy89]

manually resetting the latch isnt a big deal. what is an SCR relay and by "O/P" do you mean the outputs? also, do you have a link to some possible components that i can use in my application?

 

[riceboy89]

is there a relay that remains at the last state even if power is removed? like if a relay is powered and clicks right, is there one that will stay right even though power is taken away? is it called a solid state relay or something?

 

[dsp_]

is there a relay that remains at the last state even if power is removed? like if a relay is powered and clicks right, is there one that will stay right even though power is taken away? is it called a solid state relay or something?

There are *guess* latching relays, which are usually used in electrical installations.
Why don't you use a flip flop as suggested?

 

[VSMVDD]

you can use any gate as a latch

simply route its output back to the inputs

here is a sample design

youll need proteus vsm lite or pro version

www.labcenter.co.uk

it will open and run with the demo version

this app is also in this months elektor mag

 

[Gorgon]

is there a relay that remains at the last state even if power is removed? like if a relay is powered and clicks right, is there one that will stay right even though power is taken away? is it called a solid state relay or something?

Yes, there are latching relays. You have at least 2 types, with separate coils for each direction and the same coil powered reversed. The first type is easiest to use for a simple project like yours.

Solid state is not relays, it's normally only silicon, or semiconductors.

Any simple electronic latch will not keep the state if power is removed. To do this you need a nonvolatile element in the latch, like battery, eeprom or a big capacitor. The battery and the capacitor will revert to the non active state after some time.

TOK

 

[riceboy89]

sorry i didnt post earlier. so this kind of relay will hold the last state it was set in? can you please link me to one i can use? i can power it using anything from 0v-9v. ive looked online lots and im not so sure what kind to use.

thanks alot for all the help so far guys!