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RogerH

Electronic flasher relay

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Hi Folks,

I have a Vehicle Wiring Products flasher relay (RFL5)

I am also using one of the audio buzzer units that Johnny 250 was producing a while ago.

The alarm works well but I have noticed that when the engine is running there is a faint glow from the alarm LED

I have changed the dropper resistor from 6K8 to 27K ohms but the faint glow still glows faintly

There is no faint glow when the ignition is on but no revs.

The flasher unit definitely clicks when operating but is desctibed as 'electronic'.

So what could be causing the faint glow !!!!!!

 

Roger

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That really depends on how you have it wired up Roger so I'm guessing a bit here as I'm not familiar with the technical spec of either the relay or the buzzer. I take it the audible buzzer is connected to the same terminal on the flasher relay as the tell-tale lamp and that by 'alarm led' that is what you mean?

That means the buzzer may be the source of the voltage and if its a passive electro-magenetic one it is just possible it is picking up ignition noise from somewhere and feeding that to the lamp. As it is a very small current already, increasing the dropper resistor isn't going to make much difference.

A simple check would be to disconnct the buzzer and see if the glow is still there. If it is, the source is the flasher relay itself.

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Hi Rob

the buzzer (12v) is in parallel with the LED& resistor.

The 12v come from the flasher warning light output.

I'll try your idea. I'll also connect to the buzzer to the line that goes to the flasher switch.

 

Roger

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Yes I did a forum search and found the video of him making it so I see what you have now Roger.  Its a piezo-electric buzzer so less likely to do what I guessed as there will be drive electronics inside it to generate the 'beep' frequency.  

Perhaps more likely then that it's something to do with the flasher relay itself. 

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I have noticed this on the flasher unit I recommend to people (& supply along with my own LED bulbs)

This effect is I think due to the fact that you have replaced the normal warning bulb with an LED type, which requires a lot less current to light up,

so much so, that even a few microamps will be enough to make it glow dimly. The wiring between the flasher unit & the bulb is most probably picking up a bit of induced AC voltage behind the dash (say from ammeter wires) this comes from the ripple on the alternator output voltage. (which is why it only does it when engine is running).

you could try putting a normal bulb back in, or just live with it (which is what I am doing !)

Bob.

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Hi Bob and Rob,

thanks for your input.

I suspect you are right about parasitic something or the other. 

Johnny250 doesn;t mention this with his design. I'm sure he used the original flasher unit.. But that shouldn't affect the parasitic situation.

Perhaps a poor quality LED may help rather than a Hi-brightness one.

 

Roger

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I wonder whether bridging the pins on the buzzer with a (say) 150 Ohm resistor  might help?  It  does mean the relay has to provide an extra 100mA or so, but the low impedance might stop the pickup. 

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Hi Rob,

as my gaffer use to say years ago - that is another string to my elbow.

 

I'll give them all a try tomorrow.

 

Roger

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Recently, I fitted a trafficator unit with click from Classic Car LED, and I have an old piezzo electric buzzer connected in parallel with the connection which feeds my dash lamp, which uses a conventional bulb.  The piezzo buzzer has been in place for years, and I have kept it because my car is very noisy and I can scarcely hear the click!  The benefit is that the electronic unit keeps a steady pace, even when running for a long time - the poor old bimetallic strip (original) flasher tended to become irregular when used for more than a few seconds.

I haven't noticed the bulb behaving oddly, either with engine running or not running.

When the engine is not running, I get a click, a buzz and a flash on the dash - as one would expect.

When driving, the piezzo tends to drown the click, and it (piezzo) does some double buzzes, which it did not do when used with the old (original) trafficator unit.  I have no idea why!

Ian Cornish

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The clue here is "conventional bulb"

Bob.

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There has been a lot of comments on the flasher especially with it being inaudible. Has anyone actually tried just extending the wires and moving it up behind the dash in front of the driver, maybe even mounting it on a  thin piece of stainless to amplify it?

Must admit I never bothered as I fitted a motorcycle buzzer that comes on after IiRC ten ‘flashes’ and resets itself if you touch the brakes.

Always struck me as an odd place to stick it.... down in the passenger (for us anyway) footwell surrounded by carpet and often sweaty feet!:blink: 

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Hi Roger,

If the LED is lighting due to parastic AC ripple as Bob suggests, and I think he is probably right, then it may help to include a 10uF (25Volt) capacitor across the LED,  and possibly a silicon diode (e.g. 1N4007), or suitable Zener diode, in series with the LED since that  increases the voltage required to light the LED. You may need to adjust the Resistor to get the ideal LED output.

Kind regards

Tony

Edited by tthomson

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