break up long pulse from relay

I added a relay to flash lights and honk horn when I lock the doors with my remote....Everything works great but the pulse is about a half second long, which doesn't sound long but the horn is too loud even for just a half second.How can I break up the pulse so the horn either beeps twice or only beeps for half as long as it currently does? If this is done by adding a capacitor, what size/type capacitor should I use and where does it go?I have a 98 Acura TL 3.2 -- thanks!!

I can't believe I just told someone to stick a sock in it. LOLJohn DeRosa (Hotwaterwizard)

Stockton California

When in doubt, try it out !

If you don't have any socks to spare :), you can just use the constant to momentary relay circuit featured on the relay circuit pages to do the job. Since it's such a short pulse output you're looking for, it should work okay with the direct drive setup pictured there.

Yeah, that looks good- Since the timing is affected by the relay being used, a heavy duty relay with a low coil resistance will give a shorter pulse time and the honk will be shorter. Just diddle around with the cap values to get the toot you want; use the smaller cap for a shorter honk.

Just a comment for anyone using the big cap setup; since it'll most likely have to be a polarized electrolytic to get that kind of capacitance, make sure the polarity is wired correctly, with the positive side to the 12V, as shown in the diagram. They don't take reverse polarity connections too well, so don't just connect it up any ole way, double check the polarity before powering it up. If you don't need to pulse it in rapid succession, you can use a larger value of resistance (the 10k resistor) to reduce the standby drain on the battery (12V / 10k = 1.2mA).   All that will mean is that it'll take longer for it to discharge the cap and reset for a second pulse output. Whether that's important is up to you.

Thanks for the help guys. I'm going to try this with a 470uF cap and a 10k resistor.... 1. Do I need a diode connecting pins 85 and 86 as pictured? And if it's not too much trouble, I was wondering why a diode would be needed there? 2. I got a 470uF axial capacitor with arrows on it that point in one direction. Do I wire this in with the arrows pointed up?

petie-tl wrote: Do I wire this in with the arrows pointed up?

Just to clarify, I meant "pointed up" as in the same direction that is shown in the above diagram. Also, just wondering.... if I were to forget about the cap and resistor, and use a piezo buzzer (that has one red wire and one black) instead of the Horn(-) in the above diagram, would I need to add another relay? How would I wire up the piezo buzzer instead of the horn?petie

'98 Acura TL 3.2