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

Sorry, I didn’t include the multiple choice answers:

1. 700Hz only
2. 710Hz only
3. 690Hz only
4. 710Hz and 690Hz only
5. Any of the three frequencies might possibly be heard by the person in the blue car

Do you still think you need to know the speed of the second car to answer?

 

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

Look at post #36 to see why I posted it in this thread. I was doing research for this thread and got the laughable AI response I posted.

 

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

Going off topic is how we often have a little fun here.
Don't see any harm in that.

 

How about, for the low frequency buzzer, visiting an OLDER HARDWARE STORE???Such buzzers were rather common at one time, and an older store may have one in stock. Then mount the buzzer inside a larger, inverted, can, for protection. It will also boost the sound level, and be able to protect the batteries as well.

 

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


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 .

The gate could call you (on the landline) and complain that it has been left open.

 

How about, for the low frequency buzzer, visiting an OLDER HARDWARE STORE???Such buzzers were rather common at one time, and an older store may have one in stock. Then mount the buzzer inside a larger, inverted, can, for protection. It will also boost the sound level, and be able to protect the batteries as well.

https://www.ebay.com/itm/196523233013

 

Do you still think you need to know the speed of the second car to answer?

I can't tell. Remember, I'm somewhat color blind, so I might not be able to hear the blue car. Unless it has a little red on it. Then I'll know it's purple and hear it.

mount the buzzer inside a larger, inverted, can, for protection.

Try that around here and you'll have European Paper Wasps nesting inside it. Round here is Utah. But I'm sure they're pretty much country wide. Likely even Internationally.

 

If the paper wasps mind the noise they may be unpleasant about it. In that case, screening the opening would be in order.

 

I'm going to try the beeper and schematic that Sghioto suggested (post #29). Have some "honey do" things with more priority (happy wife, happy life) so this gate beeper has a lower priority for now. Thanks all for your contributions to this thread.

I also have to decide on the color of the case to hold the gate beeper so that it will sound at the correct frequency ....

 

I also have to decide on the color of the case to hold the gate beeper so that it will sound at the correct frequency ....

You should check out the jokes thread

 

Help me design a gate open beeper

May be circuit diagram below will help you in your design...
============================
High efficient, loud beeper.
Works at resonant frequency of dynamic speaker.
Average power, consumed from 1.5 V cell is 4.5 mW.
Speaker mounted upside down tightly to hard surface.
Closed volume of air between cone and mount surface
works as spring, increasing speaker resonant frequency.

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May be circuit diagram below will help you in your design...
============================
High efficient, loud beeper.
Works at resonant frequency of dynamic speaker.
Average power, consumed from 1.5 V cell is 4.5 mW.
Speaker mounted upside down tightly to hard surface.
Closed volume of air between cone and mount surface
works as spring, increasing speaker resonant frequency.

View attachment 330649__View attachment 330656

Thanks for your design. Will put it on my list of circuits to try.