Can anyone see a flaw in this ?

Seems to be the simplest way I can think of keeping the MOT tester happy, and making the wiring simple.

The buzzer grounds thru the brake lights, so when sitting at a junction, you can put your foot on the brake and the buzzer gets 12V at each side and so is quiet, then when you start moving again, it beeps to remind you to cancel the indicators, the dash light is there as a secondary reminder.

I could use a bridge rectifier in the middle rather than 4 diodes, it needs to power 2x 21w bulbs at the rear, and 2 x 5W bulbs at the front, and one dash bulb/buzzer. so say 60W total, thats 5 Amps, so a KBPC601 should do the trick.

[Edited on 23-2-16 by ken555]

[Edited on 23-2-16 by ken555]

How about using a 2-pole changeover switch for the hazards? One pole can switch the power supply to the bottom relay between the switched and permanent 12V, while the other can switch pin 49a of the same relay between the column switch and the bridge rectifier. No need for the top relay then.

Don't you need a specific hazard warning light on the dash though? If so, a lamp between the input to the bridge rectifier and 0V would do.

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Originally posted by SteveWalker
How about using a 2-pole changeover switch for the hazards?
Don't you need a specific hazard warning light on the dash though? If so, a lamp between the input to the bridge rectifier and 0V would do.

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The hazard warning lamp "tell-tale" maybe a separate light or the same as the indicator "tell-tale". However , it must be a flashing light.

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Tell me if I'm misreading what you're doing but, if the buzzer is finding ground through the brake lights, they're going to flash in time with the indicators while your foot is off the brake.

Dominic


[Edited on 24/2/2016 by TheGecko]

quote:

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Originally posted by TheGecko
Tell me if I'm misreading what you're doing but, if the buzzer is finding ground through the brake lights, they're going to flash in time with the indicators while your foot is off the brake.

Dominic


[Edited on 24/2/2016 by TheGecko]

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quote:

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Originally posted by TheGecko
Tell me if I'm misreading what you're doing but, if the buzzer is finding ground through the brake lights, they're going to flash in time with the indicators while your foot is off the brake.

Dominic


[Edited on 24/2/2016 by TheGecko]

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If I understand the diagram correctly as it stands, I *think* that pressing the brake would send power through the buzzer AND through the dash light (in series) so you'd get a low sounding buzz and a dim dash light.

Nothing would flash because of the right hand pair of diodes preventing and current travelling to the left side of the circuit?

All of this would be in parallel to your brake light so you shouldn't see too much of an effect in it's brightness?

Edit: Also to add on the other part of the discussion, using the indicators or hazards will send power through the buzzer AND brake lights (in series) so your buzzer will not sound as loud and your brake lights will come on dimly?

Or I could be talking rubbish....

Perhaps just earth the buzzer somewhere else?

Henry

[Edited on 24/2/2016 by z2000]

[Edited on 24/2/2016 by z2000]

Bit puzzled about a bridge rectifier in a dc circuit....there are much better ways of achieving the same goal....

Nothing wrong with the B R its just 4 diodes serving a logic purpose

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Originally posted by ReMan
Nothing wrong with the B R its just 4 diodes serving a logic purpose

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the first diagram does have one significant flaw,
if you have the hazards on, and leave an indicator on, with the ignition off, everything that is powered from the 'switched live' will be on in time with the flashers.
a simple solution to this is using just one flasher relay, powered from the permanent live; or to add another diode in the switched feed.

edit

hazard

another edit, slightly simpler


hazard

[Edited on 24/2/16 by gremlin1234]

ok, I've not given this as much tough as you have, but why not use a conventional circuit with dpdt hazard, example pulled from web e.g.

fit the buzzer across the dash lamp.

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Originally posted by 02GF74
ok, I've not given this as much tough as you have, but why not use a conventional circuit with dpdt hazard, example pulled from web e.g.

fit the buzzer across the dash lamp.

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Dont think so. Flasher unit has bimetallic strip that is heated when circuit is completed. It makes contact when cold so lights are on. Once heated, the strip bends so no conract, lights go off and strip cools .... until contact is made again and the cycle repeats.

Downside is indicators would flash when ignition is off, remedied by a relay from ignition switch.

quote:

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Originally posted by 02GF74
Dont think so. Flasher unit has bimetallic strip that is heated when circuit is completed. It makes contact when cold so lights are on. Once heated, the strip bends so no contact, lights go off and strip cools .... until contact is made again and the cycle repeats.

Downside is indicators would flash when ignition is off, remedied by a relay from ignition switch.

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Yes. Sorry. My bad. Good job someone is paying attention.

In fact i remember having this on my land rover, solution is either have two dash lamps, one for each side as on my kit car else use diodes as i did on my landrover, think it was similar to the BR as posted earlier.