Piezo buzzer for LED flasher?

I have built the flasher found here; https://www.instructables.com/id/LED-Flasher-automotive-or-motorcycle/ It works great with the LED turn signal bulbs on my bike I would like to hook up a piezo buzzer to the flasher that buzzes when either the right or left signal light is on (motorcycle flasher reminder buzzer). What would be the easiest way to do it? The flasher runs constantly when the key is on, only powering the turn signals when the turn switch is activated right or left. The buzzer won't work when hooked up to the B+ and load terminals like it was on the mechanical flasher with incandescent bulbs. I figure the problem is that the incandescent bulbs provided the ground for the buzzer though the filaments. Does this sound right? Thanks. Sorry about the long diatribe.

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AndyGadget7 years ago
Add two diodes as shown so that the buzzer is energised whenever one of the indicator LEDs in activated.
AndyGadget, will that work with an automotive circuit, say an '85 Volvo 240 with electronic turnsignal flasher but incandescent bulbs? I remember the old Champion Auto Parts stores used to have a simple fuse block clip-on piezo buzzer for turnsignals but I never bought any. Wish now I had. Windows down, can't hear the turn signal click or see the light during the day. This would be a great answer.
As long as you've got 12v switched to the bulbs by the flasher stalk you should be able to use this circuit. It won't work if the bulb is permanently connected to the positive and the stalk switches it to ground, but I don't think many vehicles are wired that way as it means less wiring if the indicators can have one side connected to the chassis (ground).
Thanks, Andy, I'll give it some more research. Not sure how my Volvo's wired but it should be rather simple. I know I don't have a thermo flasher. It's the new style electronic flasher. Will that make a difference? I'm not sure of the flasher wiring but I keep thinking there must be a way, when the flasher is energized to either of the turn circuits, right or left, if a voltage could be taken from the flasher output to fire the piezo buzzer regardless of which circuit the turn signal stock selects. If the piezo wouldn't draw too much current and screw up the flash sequence. My thought would be that wiring it that way would be somewhat simpler. If it would work.
Normal piezos are very low current, so aren't going to affect the flasher operation. I can't find a wiring diagram specifically for a 240, but looking around a bit, the commonest arrangement seems to be : 12v . . . flasher unit . . . flasher switch . . . indicator bulb . . . chassis. If it's an electronic flasher you may be able to just put the buzzer on the output of the sounder unit and not need the diodes. The difference is that a thermal flasher output will be at 12v when flashers are off, whereas an electronic flasher unit will be at 0v and only pulse to 12v when the switch is operated.
That's my thinking and what I'm hoping. Will let you know the results.
pofarm (author)  northerner310b7 years ago
This is the set up I used with the electronic flasher I built (link in my 1st post) and LED turn signals. It works great. Thanks, AndyGadget. It should work with any type of flasher system, I would think.
pofarm (author)  pofarm7 years ago
BTW, I have used these buzzers on older bikes with bi-metal flashers, also. Some bikes came with them from the factory. They used to be a fairly common aftermarket add on, too. They connected directly to the flasher between the B+ and load terminals. There are two reasons I couldn't connect one to the home made flasher like this. First, the way the flasher is made, it cycles constantly as long as current is supplied to it which, in this case, is anytime the key switch is on. The second reason is because the bulb filaments provide the ground for the buzzer, which you can't get with LED's.