Latch Circuit

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
Michael-love-electronics
Posts: 84
Joined: Tue Nov 26, 2002 1:01 am
Contact:

Latch Circuit

Post by Michael-love-electronics »

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
Posts: 140
Joined: Fri Sep 26, 2003 1:01 am
Location: Tennessee
Contact:

Re: Latch Circuit

Post by John Paul »

How about a latching relay on the alarm.
russlk
Posts: 563
Joined: Thu Dec 06, 2001 1:01 am
Location: New Hampshire
Contact:

Re: Latch Circuit

Post by russlk »

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
Posts: 84
Joined: Tue Nov 26, 2002 1:01 am
Contact:

Re: Latch Circuit

Post by Michael-love-electronics »

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
Posts: 140
Joined: Fri Sep 26, 2003 1:01 am
Location: Tennessee
Contact:

Re: Latch Circuit

Post by John Paul »

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
Posts: 84
Joined: Tue Nov 26, 2002 1:01 am
Contact:

Re: Latch Circuit

Post by Michael-love-electronics »

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 :) :) :) :) :)
User avatar
Chris Smith
Posts: 4325
Joined: Tue Dec 04, 2001 1:01 am
Location: Bieber Ca.

Re: Latch Circuit

Post by Chris Smith »

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
Posts: 149
Joined: Tue Oct 29, 2002 1:01 am
Location: Arizona
Contact:

Re: Latch Circuit

Post by Tommy volts »

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
Posts: 84
Joined: Tue Nov 26, 2002 1:01 am
Contact:

Re: Latch Circuit

Post by Michael-love-electronics »

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
Posts: 563
Joined: Thu Dec 06, 2001 1:01 am
Location: New Hampshire
Contact:

Re: Latch Circuit

Post by russlk »

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
Posts: 1044
Joined: Tue Dec 04, 2001 1:01 am
Location: Australia
Contact:

Re: Latch Circuit

Post by bodgy »

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
On a clear disk you can seek forever.
User avatar
Chris Smith
Posts: 4325
Joined: Tue Dec 04, 2001 1:01 am
Location: Bieber Ca.

Re: Latch Circuit

Post by Chris Smith »

Rockaby? <p>Isnt that a cousin to the Rock wallaby?
bodgy
Posts: 1044
Joined: Tue Dec 04, 2001 1:01 am
Location: Australia
Contact:

Re: Latch Circuit

Post by bodgy »

<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.
User avatar
Chris Smith
Posts: 4325
Joined: Tue Dec 04, 2001 1:01 am
Location: Bieber Ca.

Re: Latch Circuit

Post by Chris Smith »

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
Posts: 1044
Joined: Tue Dec 04, 2001 1:01 am
Location: Australia
Contact:

Re: Latch Circuit

Post by bodgy »

<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.
Post Reply

Who is online

Users browsing this forum: No registered users and 30 guests