Latch Circuit

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Michael-love-electronics
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Latch Circuit

Post by Michael-love-electronics » Sat Nov 01, 2003 2:22 pm

Hi,..<p>I've made a laser alarm that will go on when someone interrupts the laser beam, but the alarm will go off again as soon as the laser beam returns... !!!!<p>So I need please a latch circuit or any other circuit that makes the alarm works(on) even after the laser beam is back, till I manually deactivate it.<p> Thanks for all your help. :) :) :)

John Paul
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Re: Latch Circuit

Post by John Paul » Sat Nov 01, 2003 5:33 pm

How about a latching relay on the alarm.

russlk
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Re: Latch Circuit

Post by russlk » Sat Nov 01, 2003 6:32 pm

An SCR in a DC circuit will stay on until the current is interupted. Put a push button switch across the SCR.

Michael-love-electronics
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Re: Latch Circuit

Post by Michael-love-electronics » Sun Nov 02, 2003 11:42 am

Thanks for reply,... But I think that the relay will return to it's original state when the laser beam is back,.. but I don't mind to try it again. So please send me a schematic to the connection of the relay.<p> Thanks John

John Paul
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Re: Latch Circuit

Post by John Paul » Wed Nov 05, 2003 11:38 am

What I meant was:<p>I had bought a latching relay that was 'omron'
brand and when it latched it stayed latched unless you reversed the polairity.<p>But I don't know how it would be connected in your circuit.<p>John Paul

Michael-love-electronics
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Re: Latch Circuit

Post by Michael-love-electronics » Wed Nov 05, 2003 2:03 pm

Thanks John,...<p> But, What I want is the schematic for the latch circuit to be able to connect it to my alarm,.. I want a esigned circuit... <p> CAN ANYONE HELP.........?????<p> Thanks :) :) :) :) :)

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Chris Smith
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Re: Latch Circuit

Post by Chris Smith » Wed Nov 05, 2003 3:47 pm

A latching relay is nothing more that the out put positive feed from the relay out pin, going through a diode and back to the positive coil lead. <p>When the relay closes the power going through the relay is fed back through the diode and feeds and holds ON the relay. The diode stops it from turning on before you try to turn it on. <p>A break switch is usually needed to drop the power all together to reset the circuit.

Tommy volts
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Re: Latch Circuit

Post by Tommy volts » Wed Nov 05, 2003 3:53 pm

A slight modification to the design below should work. Close the contacts with your laser sensor circuit instead of water.<p>It has the SCR that Russ talked about for latching.<p>SCR Alarm Latch

Michael-love-electronics
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Re: Latch Circuit

Post by Michael-love-electronics » Sun Nov 09, 2003 1:13 pm

Thanks Tommy for this circuit,.. but, there are 2 items that I can't determine:
1- The component bet the 100Kohm and the ground.
2- "Hom-Radio Shack273-049".<p>Also What is the SCR.??? <p> Thanks very much :) :) :) :)

russlk
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Re: Latch Circuit

Post by russlk » Sun Nov 09, 2003 3:02 pm

1. is the moisture probe.
2. it is a HORN, you need a better display so you can read small print.
3. The funny symbol that is labled "SCR RADIO SHACK 276-1067". It should come with pinouts labled, anode is at the top, cathode goes to ground, gate connects to the 1K.

bodgy
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Re: Latch Circuit

Post by bodgy » Sun Nov 09, 2003 7:50 pm

If it is of any interest, Rockby in Australia have some surplus latching relays in their monthly flyer.<p>5v 1A 125ohms A$1.95 in singles or 1.76 in 10s, also some LDO voltage regulators.<p>www.rockby.com.au<p>
Colin
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Chris Smith
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Re: Latch Circuit

Post by Chris Smith » Sun Nov 09, 2003 8:13 pm

Rockaby? <p>Isnt that a cousin to the Rock wallaby?

bodgy
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Re: Latch Circuit

Post by bodgy » Sun Nov 09, 2003 8:21 pm

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Chris Smith:
Rockaby? <p>Isnt that a cousin to the Rock wallaby?<hr></blockquote><p>Hop over to Melbourne and see, now Rock Melons - nice.<p>
Colin
On a clear disk you can seek forever.

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Chris Smith
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Re: Latch Circuit

Post by Chris Smith » Mon Nov 10, 2003 2:19 pm

I thought you were in the North, gold coast? <p>If you stop in Sydney, Eat at Sr Nilas, a great mexican joint on the north shore?

bodgy
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Re: Latch Circuit

Post by bodgy » Mon Nov 10, 2003 7:57 pm

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Chris Smith:
I thought you were in the North, gold coast? <p><hr></blockquote><p>Correct! Until I sail back to the UK, via Byron Bay got to see what a new millenium hippy town looks like.<p>Rockby are in Melbourne.
On a clear disk you can seek forever.

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