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Instead of relays, you can use transistors for switching your car horns.

For my latest car horns for bicycles setup, I used an IRFZ44N N-channel MOSFET instead of a relay. MOSFETs use less current than relays and switch faster. So far, it seemed to work as well as relays. The pictures of my setup are in the next pages.

Step 1: Horn Setup

Step 2: Horns on Bicycle

<p>Its a long time since I played with electronics.( not this centuary) I had to stack 3 MOSFETs to handle the modest 18amps for an early experiment in electric flight. I see from the spec sheets that one can handle about 50amps, that makes things a lot more viable.</p>
<p>And for the horn you even won't need any cooling since it switches only for a second or so. Else, for long time switching, you eventually need cooling if operating a MOSFET in its border range.</p>
That looks like a fun, easy one to save! :). Your bike project reminds me of when I had a Honda Helix scooter I had bought since a car wasnt in my budget but I wanted something new and reliable. The scoot was awesome but people on the freeway often dont see 2 wheelers :/. The factory horn, like those on most cars, SUCKED!! <br>Soooooo I bought a set of air horns! Woo!! Mounted them under the rear fender well.<br>Theres nothing like seeing a car coming into your lane because they didnt do a head check, hitting the horn button and watching someone poop their pants thinking a big rig is there!! Hehe

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Bio: Autistic person who's interests include in utility cycling, recreational cycling, cycling safety, electronics, gardening, Arduino, and LEDs.
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