LED indicators

[Guest diesel_jim]

Anyone happen to know off hand what size resistor is needed to make an LED bulb fool the flasher relay into thinking that it's got 4 normal filament bulbs?

I tried WVP, but they were less than helpful

[madmatt]

Anyone happen to know off hand what size resistor is needed to make an LED bulb fool the flasher relay into thinking that it's got 4 normal filament bulbs?

I tried WVP, but they were less than helpful

Dunbri sell the ballast units just wire them in one on each indicator unit thats how I did it.

[BogMonster]

Blimey, A level physics <digs into back of mind>... as my old Physics teacher would say "Right you lot lets do some sums"

P=IV thus a 21W bulb would be 21=Ix14 (ish) so the current draw I will be 21/14 or about 1.5A

V=IR thus 14=1.5 x R so resistance R of a 21w bulb should be 14/1.5 about 9.33 ohms per bulb

Remember that if you have bulbs in parallel the resistance reduces rather than increases so you will need more sums depending on how many bulbs you are driving

Depends on what voltage the wattage rating is calculated at but I would assume the operating voltage 14V rather than the engine off voltage of 12.5ish.

Begs the question - what is the point in installing low power LED bulbs then putting in resistors which soak up the same amount of power as a filament bulb, which brings you back to square one but at several times the cost

[Guest diesel_jim]

Blimey, A level physics <digs into back of mind>... as my old Physics teacher would say "Right you lot lets do some sums"

P=IV thus a 21W bulb would be 21=Ix14 (ish) so the current draw I will be 21/14 or about 1.5A

V=IR thus 14=1.5 x R so resistance R of a 21w bulb should be 14/1.5 about 9.33 ohms per bulb

Remember that if you have bulbs in parallel the resistance reduces rather than increases so you will need more sums depending on how many bulbs you are driving

Depends on what voltage the wattage rating is calculated at but I would assume the operating voltage 14V rather than the engine off voltage of 12.5ish.

Cheers for that Stephen... i couldn't be arsed to get my brain in gear!

Begs the question - what is the point in installing low power LED bulbs then putting in resistors which soak up the same amount of power as a filament bulb, which brings you back to square one but at several times the cost

It's not for me,'tis for a forumeer here; i've got plain NAS lights, good enuff for me. although the LED ones do look snazzy

[Logic]

Blimey, A level physics <digs into back of mind>... as my old Physics teacher would say "Right you lot lets do some sums"

P=IV thus a 21W bulb would be 21=Ix14 (ish) so the current draw I will be 21/14 or about 1.5A

V=IR thus 14=1.5 x R so resistance R of a 21w bulb should be 14/1.5 about 9.33 ohms per bulb

Remember that if you have bulbs in parallel the resistance reduces rather than increases so you will need more sums depending on how many bulbs you are driving

Depends on what voltage the wattage rating is calculated at but I would assume the operating voltage 14V rather than the engine off voltage of 12.5ish.

Begs the question - what is the point in installing low power LED bulbs then putting in resistors which soak up the same amount of power as a filament bulb, which brings you back to square one but at several times the cost

While the calculation is correct, the voltage would need to be calculated at 12V as a vehicle indicator bulb is rated at 21 watts of power at a voltage of 12 (or whatever else is on the 'bulb'). Therefore 21 / 12 = 1.75amp, then 12 x 1.75 = 6.857 ohms.

I don't actually know for sure the effect of having higher/less resistances on the flasher as I have never felt the need to try, but I'd guess that the flashing speed difference would be considerable since there would be two 'bulbs' (or more if towing?). 2 resistances in parallel is calculated by (R1xR2)/(R1+R2), and 3 or more by 1/Rt = 1/R1+1/R2+1/R3 etc (sorry I don't know how to correctly display the '1 over R total equals 1 over R1 plus 1 over R2 etc.).

The EASIEST way would be to get a working 'cold' bulb (resistance changes proportionately with temperature) and put your ohmmeter (multimeter) across the terminals and this would give you an exact resistance - remember to subtract your multimeter lead resistance value.

Dennis

[LandyManLuke]

Begs the question - what is the point in installing low power LED bulbs then putting in resistors which soak up the same amount of power as a filament bulb, which brings you back to square one but at several times the cost

Indeed!!!!

The way to solve the problem properly is to swap the flasher relay for an LED compatible flasher unit. as you've said, the alternative is a bodge with no energy saving effect. Of course you still get the quicker response time and the resistance to vibration etc.

[muddy]

Of course you still get the quicker response time and the resistance to vibration etc.

You missed one....

Bling!

[madmatt]

Begs the question - what is the point in installing low power LED bulbs then putting in resistors which soak up the same amount of power as a filament bulb, which brings you back to square one but at several times the cost

Er because it saves changing bulbs when the dam things pack up after a couple of trips in and out the quarry in a day. on our 130 the cheap cack land rover units and bulbs were a right pain in the neck.

Swapping the flasher unit is all well and good until you have to tow trailers with cnventional indicators.

[landmannnn]

Swapping the flasher unit is all well and good until you have to tow trailers with cnventional indicators.

A conventional flasher unit uses the current to flip a bi-metallic contact. An electronic flasher just turns on and off - most are compatible with any mix of led and normal bulbs. Do a google search for electronic flasher unit.

[pete3000]

Jim, have a look at www.ultraleds.com

they used to do ballast resistors 1 needed for each side of vehicle (2).

now they seem to do a replacement flasher relay instead not sure if it is any good though?

search "flasher" in quickfind box on their website. N.B (stranger results may appear on google)

for resistor calculation would be maybe be 21w+21w+5w on each side =47w/12v=4ish amps

12v/4A equals 3 ohms. and suggest a power resistor such as a 25watt which can be bolted to rear tub by light cluster.

any less than 3 ohms and the trailer flash may spring into action as you add more current draw.

only my thoughts, no guarantees

Pete

[The Badger]

Anyone happen to know off hand what size resistor is needed to make an LED bulb fool the flasher relay into thinking that it's got 4 normal filament bulbs?

I tried WVP, but they were less than helpful

VWP will not have one, but these guys do have one.

The reason I would go for the relay swap is because you can then always go back to bulbs if you need to.

You can also just swap out the normal bulbs for LED's, and swap the relay - easy - no wiring

Got some kick ass work lights from them too, both only need a 5am fuse and they are really really bright....

I have swapped all my bulbs for LED's from ultra LED's, but don't bother calling them because the customer service sucks, in fact I had to tell them that, then they actually helped..... (sort of)

Also the make sure you get the correct rear stop tail LED's, as I used the zenon ones and they did not work, but that was when they did not sell the reverse polarity version. And this version will work on my 90 (it's an 07 one), so just check.

[madmatt]

A conventional flasher unit uses the current to flip a bi-metallic contact. An electronic flasher just turns on and off - most are compatible with any mix of led and normal bulbs. Do a google search for electronic flasher unit.

When i fitted my LED units (not replacement bulbs) nearly two years ago there wasn't that sort of flasher unit availiable at a sensible price . Thanks

[pete3000]

VWP will not have one, but these guys do have one.

The reason I would go for the relay swap is because you can then always go back to bulbs if you need to.

You can also just swap out the normal bulbs for LED's, and swap the relay - easy - no wiring

Got some kick ass work lights from them too, both only need a 5am fuse and they are really really bright....

I have swapped all my bulbs for LED's from ultra LED's, but don't bother calling them because the customer service sucks, in fact I had to tell them that, then they actually helped..... (sort of)

Also the make sure you get the correct rear stop tail LED's, as I used the zenon ones and they did not work, but that was when they did not sell the reverse polarity version. And this version will work on my 90 (it's an 07 one), so just check.

mmmmmm....... shiny goods! prices are not too bad but more than I want to pay at the moment.

have you seen these people for worklights/switches/flashers etc...etc.

http://www.emergencyequipmentshop.co.uk/wo...4b6c11312b3ea3a

Pete

[Aragorn]

remember though that if you use a resistor it will need to be rated to handle the wattage your "emulating"

so if your using one 6ohm resistor in each corner it will need to be rated to at least 21w

[pete3000]

Aragorn, too true, no good using 1-2 watt resistors needs to be a power heatsunk version.

You only need two though at 3 ohms 25 Watt as this produces the same effect as four 6 ohms in each corner. If you check the good old haynes or lr wiring diagram there are only two circuits (left and right) with 2 or three bulbs hanging off each side of the flasher unit/indicator stalk. Green/white and Green/Red leaving the switch/relay IIRC? this is the case on early defenders and 110's I have worked on anyway.

The other reason for a 25W resistor rather than a 50W (with 3ohm) is the flashers are on a 50% on/off duty cycle (or less if you haven't broken down) so 100% load is never seen.

Pete

[The Badger]

mmmmmm....... shiny goods! prices are not too bad but more than I want to pay at the moment.

have you seen these people for worklights/switches/flashers etc...etc.

http://www.emergencyequipmentshop.co.uk/wo...4b6c11312b3ea3a

Pete

yeah had a look at them, I was not into the quality, true you can get good stuff at a good cost, but it is also true that if you pay peanuts, you get monkeys. Even though I would like a pair of monkeys stuck on the back of my wagon as they could be trained to be quite useful.

[steven Hart]

Try 1 of these as you will not need resistor

Ultraleds

I believe its from a BMW so you might be able to get 1 elsewhere