Be sure to look for a special low frequency one. Normal ones are 3115 Hz.

 

Another option Here

 

OK, here's my schematic (Less resistor values and cap values) OH! The battery is 9V.
View attachment 329993

Thanks for going the extra mile to post your info!
So you're using the LM385 as a time delay to then sound the continuous alarm?
I would like to have a beeper rather than a continuous alarm for 1) intermittent beeping would be less annoying and 2) less power used to sound the buzzer.
Thanks.

 

It would seem that a continuous sounding horn would be annoying, both to you and any neighbors.
You could add a timer circuit to activate the horn for a short beep every few seconds.

Agree. Short beeps would be less annoying and also reduce the on time of the buzzer to save battery power.
Thanks.

 

I have some of these. Automotive squeaker. They might pull too much power but it is place to look. There is also the seat belt not connected squeaker. Place these at head high and you will hear them.
View attachment 330003

I've tested my hearing using online tone generators. 400Hz - 1KHz is the best frequency range for me. I assume that this small unit's frequency is probably in the 2500+ Hz range. Too high for me. Thanks

 

LOL; yes! My neighbor had an annoying barking dog. He put a shock collar on him. He quickly learned to be quiet when wearing the collar. But it was recommended not to put the collar on the dog for more than 12 hours at a time. So the dog learned that when not wearing the collar it was permission to bark. And this dog would aimlessly bark at nothing. Just felt the need to express himself. THEN other dogs in the neighborhood would hear him howling and they'd start. Which would egg him on.

LOL ... Our dog is a Border Collie and she's very smart. She would learn that trick in a heartbeat.

Perhaps a more expensive route to go would be to use a bluetooth or Wi-Fi transmitter that would signal you on your phone when the gate was open. No need for audible alarms or anything else that the dog would learn from.

I don't carry my mobile phone while I'm at home. Just rely on our landline phones that ring throughout our house. Old school .

 

Another option Here

That unit would be perfect as long as it doesn't work like a 400Hz buzzer that I bought from Amazon. The Amazon buzzer was barely audible when not mounted. It required firm mounting to a surface that can vibrate to act like a speaker. Then the sound level was satisfactory but to mount it on a suitable surface was the problem.

I'll try to do further research on the unit you linked to. Thanks.

 

Be sure to look for a special low frequency one. Normal ones are 3115 Hz.

Will do. Thanks again.

 

I'll try to do further research on the unit you linked to. Thanks.

This is a circuit to pulse the buzzer.
There is a 5 second delay when Sw1 is first activated then emits a 1/2 second beep every 4 seconds with the values listed.

 

This is a circuit to pulse the buzzer.
There is a 5 second delay when Sw1 is first activated then emits a 1/2 second beep every 4 seconds with the values listed.
View attachment 330036

Looks good! Thanks much for finding the low current 450Hz buzzer and your schematic. I'll follow up on verifying that the 450Hz buzzer will be loud enough. Thanks again!

 

LM385 ?
Do you mean a LM358 ?

Will have to check into that. You could be right. Probably are.

Thanks for going the extra mile to post your info!
So you're using the LM385 as a time delay to then sound the continuous alarm?
I would like to have a beeper rather than a continuous alarm for 1) intermittent beeping would be less annoying and 2) less power used to sound the buzzer.
Thanks.

Gave you this simply as food for thought.

 

Once again I am going to suggest using an "off the shelf" kid's type bicycle horn. They come in a weather resistant package that also holds the batteries. Only the switch is external, connected to the two wire cable that is part of the package.

 

Once again I am going to suggest using an "off the shelf" kid's type bicycle horn. They come in a weather resistant package that also holds the batteries. Only the switch is external, connected to the two wire cable that is part of the package.

A bicycle horn as you describe would fit the bill nicely if it is a low frequency horn.
I've been searching on Amazon and the electronic bicycle horns that have video reviews appear to use piezo buzzers so are rather high in frequency. Many use two button batteries which seem rather underpowered. And some use rechargeable battery which would not work for my situation.

If anyone knows of a low frequency electronic bicycle horn, please post a link.

Thanks for the nice suggestion.

 

I was thinking more in the line of what I have seen in stores. And I am NEVER impressed by what the artificial intelligence of online shopping software thinks I should be interested in.
The bike horns that I am thinking of all have electromagnetic buzzer arrangements driving a metallic diaphram. Of course it may be that those are a bit obsolete. Probably what I am thinking about would be available at an older bicycle shop, maybe on a shelf in the back room, so that you would need to ask about it.

 

I was thinking more in the line of what I have seen in stores. And I am NEVER impressed by what the artificial intelligence of online shopping software thinks I should be interested in.
The bike horns that I am thinking of all have electromagnetic buzzer arrangements driving a metallic diaphram. Of course it may be that those are a bit obsolete. Probably what I am thinking about would be available at an older bicycle shop, maybe on a shelf in the back room, so that you would need to ask about it.

If I can find an electronic bike horn in the 400 - 1K Hz frequency range, that would save me from a lot of work. I'll keep looking. Thanks for the nice suggestion.

 

I asked google what was the frequency of a car horn. This was a part of the AI response:

The frequency of a car horn can range from 200–500 Hz, but can also be as high as 2400 Hz. The frequency of a horn is often related to the size of the vehicle. For example, a red car moving west on a road may produce a loud sound with a frequency of 700 Hz.

Who knew the color of the car and direction of travel had anything to do with it!

 

It has been a long time since an answer has made me laugh this much!! I was not aware of the vehicle color affecting the horn output. Thanks to AI we can now be aware of this.

 

I suspected the AI fail I showed in post #36 was a result of it misinterpreting a text about doppler shift as saying something about the frequency of a car horn. So I searched, and found this text:

Question
A red car moving west on some road is creating a loud sound with a frequency of 700Hz. A blue car is also travelling west along the same road. A person in the blue car hears the loud sound from the red car.
From the following list of frequencies, what possible frequency or frequencies might the person in the blue car hear?
1) 710 Hz
2) 700 Hz
3) 690 Hz

 

I suspected the AI fail I showed in post #36 was a result of it misinterpreting a text about doppler shift as saying something about the frequency of a car horn. So I searched, and found this text:

Which car is traveling faster? And how much faster? Are they approaching from behind or driving away from in front of the other car?

 

And aren't we just a bit off topic ? ? ?

Low frequency alarm, beeper or car horn intermittent to alert the home owner the gate is still open. Seems the biggest problem to solve is the frequency of the alert signal. Maybe paint it a different color ? ? ?