Diy hazzards

[//no.comment]

Has anyone put together there own hazard kits?
They should be pretty simple things to make, and for me it could be completely free if i "liberate" the components from the stores at uni!
When i broke down last weekend it got kinda old with everyone shouting to me to put my hazards on! braking down at a very busy roundabout junction in rush hour isnt a fun thing to do!
can any body think of any problems in the below schematic?
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the astable circuit creates the flashing pulse with a 50% duty cycle (on/off)
when the relay is activated, it moves the bulb connection from the normal flasher relay (normally closed relay connection), to a permanent 12v(normally open) connection causeing all for bulbs to flash
There is a green LED as a warning light which will also flash, which is as i understand required by law.
instead of using a 4 pole relay ill probably end up using two 2 pole relays as ill be able to get hold of these easier!
The astable will be created using a simple 555 timer.

it will simply me inserted in the wiring loom by inserting at a bayonet connector, so the wiring loom will not be altered and can be easily removed and put back to original if needed. like so:
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oh and sorry about the image quality

[alex_holden]

I think you should be able to do it with a standard 46W flasher unit and a couple of largeish diodes feeding into the two sides of the standard indicator setup.

[alex_holden]

Actually, I'm talking rubbish - of course you need a heavy duty flasher unit capable of driving all four bulbs at once.

Something like this should do the trick: http://www.autoelectricsupplies.co.uk/product/166

You can of course build your own electronic flasher unit with a 555 and a power transistor or relay, though remember it will need protection from surges and reverse voltage spikes etc. or it's likely to let the magic smoke out pretty quick (a car electrical system is a pretty harsh environment).

This is how I would try wiring it up (untested):

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L and R would tap into the appropriate bullet connectors for the left and right indicator light circuits.

This circuit will behave a bit oddly if you have both the hazards and the indicators on simultaneously. You could avoid that problem by running the supply to the common terminal of the indicator switch through another relay that disables the indicators when the hazards are on.

[//no.comment]

the advantage of my way is itd be free, i might just try it anyway!bosh a few zener protection diodes, and some kind of band pass filter in there and see what happens, have you any idea what magnitude the voltage spikes/surges would be? i cant really plug my oscilloscope in while im driving along!
i could use a power feed from the voltage regulator for the petrol gauge perhaps?
just thinkin this out aloud
Origionally i was using transistors but it all got a bit complicated with the switching!


would this flasher module work? it doesnt have any kind of specification, has anyone fitted one like this?
http://morrisminorspares.co.uk/shop/pro ... 33b42e74b0

This circuit will behave a bit oddly if you have both the hazards and the indicators on simultaneously. You could avoid that problem by running the supply to the common terminal of the indicator switch through another relay that disables the indicators when the hazards are on.

or i could just not put them on at the same time

[Jefftav]

I have fitted this type to my minor. I extended the wiring so the relay part is hidden behind the glove box and teh switch is on a panel in the car and it seems to work OK.

http://cgi.ebay.co.uk/12-Volt-Hazard-Wa ... 255a18a36d

[alex_holden]

the advantage of my way is itd be free, i might just try it anyway!bosh a few zener protection diodes, and some kind of band pass filter in there and see what happens, have you any idea what magnitude the voltage spikes/surges would be?

I've not measured it myself but I've heard people talk about spikes of thousands of volts. Only for microseconds obviously, but that's enough to blow an unprotected IC.

i could use a power feed from the voltage regulator for the petrol gauge perhaps?

It's more of an electromechanical voltage stabiliser that periodically switches on and off to maintain a rough average voltage. I wouldn't say it was suitable for powering electronics.

would this flasher module work? it doesnt have any kind of specification, has anyone fitted one like this?
http://morrisminorspares.co.uk/shop/pro ... 33b42e74b0

In the bigger photo I can see "46W" on the side. Indicator bulbs are nominally 21W so all four at once will take about 84W.

or i could just not put them on at the same time

I suspect I might forget if I broke down at a busy junction! ;)

[mike.perry]

In my experience flashers will not make any difference. My traveller broke down on a busy dual carriageway, saga of the expolding coil. Despite having the fashers on and the back doors open, cars were still almost on top of my car before they tried to drive around it.

[alainmoran]

My car-alarm comes with a great feature ... when you open any of the doors (I've fitted bonnet & boot pins too) then the hazard lights flash

It's just a cheapy off ebay, but has encrypted remote, microwave & vibration sensor & ignition cut-out all built in (as well as the natty hazard thing), it even supports central locking which I'm tempted to fit at some point!

http://cgi.ebay.co.uk/CAR-ALARM-AND-IMM ... 2c5043fac2

[bmcecosse]

You can easily do it with a '555' timer - can get it ready set up on a Vellman PMK 111 board. Something like this - http://cgi.ebay.co.uk/Brand-New-555-Ast ... 3ca652c342
But frankly - it's a waste of time! No-one will see them anyway. You would be better with a large magnetic base rotating orange lamp to place on the roof !

[frosty]

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frosty

[alex_holden]

[frame][/frame]
frosty

This does the same thing as my diagram but with a double pole relay instead of two diodes. You'll need a current limiting resistor in series with the LED too or it will go pop. I'm not sure what the "to accessories" connection on the switch is for; perhaps you mean to power the normal flasher unit from that connection instead of the ignition switched live (this would avoid the misbehaviour when both hazards and indicators are on, though it has the disadvantage that the indicators would now still work when the ignition is off).

[billlobban]

I'm a bit of a Luddite so I've got the old fashioned system in the back - a Triangle

[MarkyB]

Who do you get to play it?[frame][/frame]

[bmcecosse]

If you buy the 555 module on ebay - it has the relay incorporated! Nice diagram frosty!

[//no.comment]

trouble with using a 555 is that the IC will not be able to cope with the voltage spikes and will need some type of regulation.

what do people think to using one of these? http://cgi.ebay.co.uk/5-L7805CV-LM7805- ... 335623f206
or will that still not be good enough? the data sheet says 35v max.

i think the link that BMC pointed out on ebay is just the PCB, itd mean id have to get the exact components it was designed for, which could be a bit tricky!

frosty, what were you planning on using as your timer module?

[frosty]

frosty, what were you planning on using as your timer module?

[frame][/frame]

This timer is adjustable between 1-second to 3.5-minutes. An LED illuminates during the timing period and a buzzer sounds at the end.
Kit supplied with PCB, buzzer & electronic components.
12VDC power required. Jaycar KJ8108 $A16 ... about 8gbp

[bmcecosse]

Oooh yes - it is just the board - but maybe they will do you a kit with the parts. The 555 will be fine - don't worry about 'spikes' - put a cap across the volts if it worries you.