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Posted: Mon Jun 17, 2019 7:33 pm
by Lenp
I was recently involved with a vintage Ahooga horn project for a friend, and it was was a good example of a plan almost not coming together.

He wanted the horn to be self-contained in a carrying bag for concealment, and a wireless remote control to sound the horn.
To start with, the horn is 6 VDC at about 5 amps, and the remote receiver was 12 volts at a few ma idle. So, the choices were to use a 12 volt battery, and drop it to 6 volts for the horn, but that's way too much loss, or to use a 6 volt battery and up-convert to 12 volts for the remote. I chose the latter.

Packaging it was easy, I just used an aluminum chassis, and mounted the horn on the top with the works underneath. I had to make the bottom since it was on a long back order. While waiting for the parts I disassembled the horn, cleaned it refinished it getting rid of it's three coat brushed red paint, and did whatever else to help it survive another 75 years.

Once the parts were received the work begun. The remote was quite nice, but it had latched on/off control, with two buttons not momentary operation. I was led to understand it could be programmed for momentary, but not so. Well that was the first work around. I used an off-the-shelf timer board to make a 1 second horn blast, and it also reset the remote control. That worked great...until it was turned off then back on. The horn sounded each time it was powered because the timer went through a reset. So much for being inconspicuous! Another issue, the dumb timer's relay was normally energized, drawing 300+ ma. all the time. Again, not good!

After some head scratching I eliminated the timer and wired the remote receiver to operate a relay. Since the 6 and 12 volt feeds both share the battery common, the relay contacts broke the common to the receiver and made the common to the horn when it operated. Yes, it was only a blip sound from the horn since everything got reset so quickly but then I added a big capacitor across the receiver's power input to keep it powered for about 1 second before resetting. Now I got a decent sounding horn sound with a timed pulse.
Adding a couple of switches, an LED and the charger jack, it was near done except for a carrying bag.

At harbor Freight I found a perfect fitting tool bag, almost made to order, and it looked non-nondescript. The chassis mounted horn fit well, and it sounded great, with the bag open. With the bag closed, it sounded like Ahoo gaaagaaagaagaag! As it turns out the bag is plastic lined and the sound could not get out. The sound pressure waves were affecting the horn's diaphragm, effectively gagging it. Now who would have thunk that!

Now he has the horn and is using it with the top open, happily waiting for the next car show. He is so happy in fact that his wife is threatening to put it, and him, out of the house and probably she has made disparaging remarks about me.

One just never knows!

Re: Ahooga!

Posted: Tue Jun 18, 2019 9:39 am
by jwax
I've used those RF modules, and the $12 receiver/transmitter fob (including battery!) has the option of momentary, toggle, or latch with a single button. Nice job though, getting your one second delay from a cap!

Re: Ahooga!

Posted: Tue Jun 18, 2019 11:50 am
by Lenp
Thanks, and there's proof that every job does not need a micro!

Re: Ahooga!

Posted: Tue Jun 18, 2019 12:45 pm
by dacflyer
i like off the shelf stuff as well..makes for easier repairs.

Re: Ahooga!

Posted: Wed Jun 19, 2019 4:58 am
by dacflyer
i found a 1 button panic button that worked with a commercial alarm system. the receiver had options, on / off / and momentary.
as well as a SPDT relay.
i used one of these long ago to make a remote control model rocket launcher . worked really well within 75ft range.

here is something you might like....
a programmable remote module,, easy to use too.

and it's cheap... ... ntrol-diy/