Re: simple one-shot pulse detector circuit needed

detector out of two of transistors and a few resistors, but I can't find the circuit anywhere. Searches keep throwing up stuff about astable multivibrators and nand gates and that's not what I'm looking for.

line. The pulse comes only after several days of inactivity and should turn an LED on permanently. No reset required and any subsequent pulses must *not* turn the LED off again, so it's operating like a bistable latch (if that's the right term).

The 1 second requirement significantly complicates the solution. If any old pulse will do, use a latching relay...either magnetic latch or feedback from the contacts.

As always, the devil is in the details. How much current can you get out of the 5V pulse? What voltages are available when the pulse is not present? How do you expect to reset the thing? What are the specific details of the 1 second requirement? Timing accuracy and boundary conditions? Assume you wouldn't have mentioned it if it weren't important.

magnet/reed switch from a burglar alarm door/window ajar sensor.

detector out of two of transistors and a few resistors, but I can't find the circuit anywhere. Searches keep throwing up stuff about astable multivibrators and nand gates and that's not what I'm looking for.

line. The pulse comes only after several days of inactivity and should turn an LED on permanently. No reset required and any subsequent pulses must *not* turn the LED off again, so it's operating like a bistable latch (if that's the right term).

.. or just a resistor (eg. 4K7) to drive the gate of a 2N5064, in turn drive an LED with series resistor (4 parts). It will detect a positive pulse of any length greater than a couple microseconds by latching on, and thence cease to care about the state of the input, so the LED will stay on until the power is cycled.

Should be battery powered sensors with RF interface available for security.

Outdoors? It wouldn't last. Depending on the type of latch, one of several types of industrial position sensor would be the best bet.

I missed that part of the specification. Probably want three or more magnetic sensors physically placed and logically connected to insure that it can't be spoofed by a magnet without intimate knowledge of the design. Encase the bullet-resistant box in concrete. Probably want to put a signal into the razor wire so you can use it as a proximity sensor. Maybe a satellite phone to call the cops when the phone lines get cut. And a bluetooth connection to the alarm system with an encrypted heartbeat so it can't be jammed. Probably want at least one guard dog with a wireless heart rate sensor just in case they get put to sleep. Of course, destroy all documentation and eliminate everybody you ever discussed it with. Crush the hard drive. Grind it up into dust and scatter it at least 10 miles off shore.

If security isn't the primary requirement, there are lots of devices. The Powerhouse MS13A is a X-10 wireless PIR motion detector. You could hack a relay into that and get motion plus gate detection. They have other alarm sensors, but I don't know the numbers. There are devices designed to alert you when your mailbox door is opened. Driveway occupancy sensors. Wireless doorbells. Garage door openers. RF TV remotes.

And my personal favorite...close the damn gate. ;-)

And the gate is steel. Maybe the other way around, a coil whose inductance changes with gate position? ...Jim Thompson

-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

Some of us, often referred to as the "evil rich", EMPLOY paisanos who fail to close the gate.

I know what to do... fire 'em all ;-) ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     | 
| Analog Innovations, Inc.                         |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| Phoenix, Arizona  85048    Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

ne of

ical/index.html

-Lasse

There ya go! Thanks, Lasse! ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     | 
| Analog Innovations, Inc.                         |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| Phoenix, Arizona  85048    Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

Replace them with an electric gate closer. I still see lots of those

24 V satellite motors around. All you need are two wires to the motor, a 24V 5A supply & a reversing switch. There are a pair of adjustable limit switches inside that can be set for full open & fully closed. An On/Off switch for added safety, in case someone tries to stop it by putting their hand in the wrong place. I have a pair of 18" jacks that I'm going to use on the swung gates at the end of my driveway. A couple old C-band sat controllers for the power supplies, and an eight button RF remote for the truck. The RF remote & matching relay output receiver are about $10 on Ebay. I should have less than $20 in the pair of controllers. :)

The two eight foot pieces of 6" black iron pipe cost me a lot more than that. The old gate posts are wood, and the gates change position,, depending on the amount of rain.

There are waterproof inductive proximity sensors with all the circuitry in a little tube.

Jim said 'yard gate' and a motor is more suited for a driveway gate.

For the sensor I'd say light beam interruption over a 1-inch gap into which a little tab enters.

To close it automatically the hinge can be easily modified to use gravity, with a magnet to pull it the last centimeter hard enough to engage a latch.

Just put a shim between the upper hinge and the post, and mortise it more deeply into the gate. The magnet might not be needed.

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zero, and remove the last word.

There are such things as "self-closing gate hinge"(s), not real cheap, but if the object is to ensure the gate is closed then they beat lighting an LED.

I was considering his austic grandson. He couldn't open that type of gate by himself.

a reed switch like used for alarms...

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Perhaps it would be more productive to fix or improve the gate closing mechanism, thus eliminating the need for a weather proof switch and associated electronics? There is a wide variety of gate closing mechanisms available, usually based on a linear or rotary spring mechanism. Many can be retrofitted to an existing gate:

Then, there's the cannonball gate closer:

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

Actually I want to know that it was opened. Got a Mexican claiming he worked when he didn't :-( ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     | 
| Analog Innovations, Inc.                         |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| Phoenix, Arizona  85048    Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

Oh...

Writing software, designing gate alarms, and in general, solving problems are all easy if you don't worry about error conditions. Real problem solving is more about dealing with oversights, errors, anomalies, stupidity, and abuse, than about making it work. Whenever approaching such things, I ask "What problem are you trying to solve?" The answer often eliminates a wide assortment of obvious and usually impulsive solutions.

If you can see the gate from the house, install a security camera and DVR. I recommend the clear picture of an IP camera over the fuzzy blurr of a composite video camera. Then you can see who or what opened the gate. If the Mexican worker is clever, he'll probably "accidentally" jam the gate open and defeat your scheme. If a camera and DVR are too elaporate, a PIR motion sensor will detect the Mexican directly.

However, if you must have a gate switch, the previously recommened proximity sensors are probably good enough. A burglar alarm type reed switch and magnet will also work if you keep them away from the metal gate.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

You keep adding requirements to the spec. Often, it's useful to monitor the thing you want monitored. Monitoring attendance is no guarantee that you actually get work. Stated another way: If you can't tell if the work was done, you're paying for work you don't need.

Hire people you can trust?