LED light wiring

[SYC02T]

I have done the, 'lets pull out the guard blinkers and while were at it lets put in some LED lights'

Well as you may guess, now i do not have the current draw that the original system was designed for, so i have to look for other ways to make them flash again.

The other day i got pretty sick of pretending i was a relay and turning the blinkers on and off while there was a copper near by.

What is the best way, do i put a resistor on each output or where the wire for the guard blinker used to be. If so what kind of resistor.

Do i get creative and try and remember / work out how to use a 555 timer or something.

your thoughts?

[ViPeR_NiPPleX]

you could use a resistor in parallel with the LED to simulate the load. As to what resistance will be required is another matter. Otherwise you will want to manipulate the indicator control box, which I have no knowledge of

[RA35GT]

G'Day mate,

You could put a resistor in parallel with the led, to work out the required size you will need to measure the current the led draws (would be small), then measure the current the original bulb draws. Calculate the difference, this will be the current required to be drawn by the resistor. Using R = V / I you can work out the required resistance value (Assume a voltage of say 13.7V). You will also need to calculate the power required to be disippated by the resistor, which is P = V^2 / R. You then need to find a resistor with the appropriate resistance and power rating.

I am pretty sure you can get an electronic flasher that doesnt rely on current load to flash, this would require some rewiring to get it to work. (as would the other options)

Or you could make a astable timer circuit with the 555...if you type astable timer 555 into google you will gets lots of hits with circuit diagrams etc...

I guess at the end of the day mate, just do what is easiest for you..

Rudi

[river]

Hi,

Or you can toss out the existing "bokka" and just wire it up to a 555 circuit, and let the 555 do the flashing for you.

Best to have two identical 555 circuits - one for the left side and the other for the right side.

So, when you hit the indicator switch to turn left you activate the l/h 555 circuit and when you move the indicator for a right turn you activate the r/h 555 circuit.

You just bypass the bokka and wire the relevant indicator wires to the relevant 555 circuit.

Here's a 555 primer for you which will tell you all you need to know about this wonderful little chip.....

http://www.uoguelph.ca/~antoon/gadgets/555/555.html

seeyuzz
river

[2jzhilux]

just connect the globe up and then the leds then tape up the globe
you will know when the globe blows when your indicators blink fast again and then just replace the globe

[kme023]

Depends on how in touch with electronics you are, but i'm pretty sure as mentioned earlier that the electronic flasher is'nt current related so it should flash you're led's. Soooo much easier than rewiring..
Are the led's that you used standard led's?.... if yes remember that they only require 1.5 volt dc, and you will require a dropping resistor of about 1k.
If you used 12v leds, you're laughing!
Happy flashin

[SYC02T]

I havent done any official training, but i can understand and rewire my car, install my alarm and computer, build those jaycar kits etc.

I don't allways know exactly what/why it does on board level but i can follow schematics and instructions.

I dont want to have loose bulbs hanging under my car, i would like to fix it once and properly. especially b4 new years when it goes on its first big trip.

Any one got some diagrams, or done it b4. Some one here works at jaycar i think in silverwater.

[river]

Hi,

Alrighty.....

The 555 timer is a small 8-pin chip that can be configured for some amazing circuits. One of these circuits is called the "astable oscillator". This means the 555 will output a high then a low, then a high then a low, add infinitum. And, it does this with the addition of 2 resistors and a capacitor.

For indicators it is preferable to have the on and off times to be equal, and flashing at (say) twice a second.

The circuit you need is....



If you use the a 1k resistor for R1, a 110K resistor for R2, and a 6.8uF capacitor for C, you will get an ON time of .523secs, an OFF time of .518secs. This relates to a 50.23% duty cycle and a period of 1.04secs, which is .96Hz (which is close to 1Hz = 1second).

If you want to experiment with different values then go to http://home.cogeco.ca/~rpaisley4/LM555.html#3 which will take you to the above diagram and an on-line calculator that will allow you to enter values for R1, R2 and C - which will give you the various ON/OFF times, duty cycle etc.

For stability purposes the value of R1 should be 1K ohm (1000 ohm). The capacitor should be an electrolytic type. Also the values of R1 and R2 should be a value that is obtained from the E12 or E24 range (that is, off the shelf, easily purchased values). The capacitor should be in the E12 range, again for the above reasons.

While the output of the 555 can drive quite a few milliamps, I doubt it would be powerful enough to easily drive a few bright LEDs. Therefore, you will need to connect the output of the 555 to a transistor that is capable of driving the LEDs. Off the top of my head I'd say a BD139 transistor would suffice, but I need to know how many LEDs you are thinking of driving so I can get an idea of the total current they will require.

Now, there is a chip called the 556 which is a 14-pin device that is merely two 555 chips in the one chip. You can use one of these so both left and right indicators can be accommodated on the one chip, but 555 chips are cheap and I don't think you will save too much time or money going with a 556 rather than two identical 555 circuits.

You need to wire your indicator so when you switch it to turn left, the wire that usually goes to the bokka (for a left turn) needs to provide power to the 555 circuit so it can commence oscillating. Similarly, you need to do the same for the right hand side, which will provide power to the other identical 555 circuit.

On the other hand, you can get fancy and use just one 555 circuit, but instead of switching power to it, you switch the output to either the right or left side. This means that the 555 will be powered up and switching once the ignition is on, but none of the LEDs will flash until you move the indicator to close the appropriate left or right side LEDs circuit. The 555 uses bugger all power and it won't be an issue having it switching when the ignition is on. Also, the 555 can be powered from 5 to 15VDC, so you can connect it to your 12V car system without any issues.

Hope this helps.

seeyuzz
river

[river]

Hi,

Oh, don't forget the hazard lights. You need to disconnect the hazard switch from the bokka and connect it to your 555 circuits, so when it is on then both 555 circuits are energised to flash all indicator LEDs.

You will only require a small circuit board for the above circuits and fit then into a small pastic jiffy box or something similar and attach it under your dash. Then you need to find the wires to your indicators and attach them to the output of the 555/transistor circuit.

You can use a small 8-pin socket to fit the 555 chip, but it may work loose with vibrations from the car and therefore I recommend you solder in the chip.

seeyuzz
river

[river]

Hi,

Just thought about it, and you'll definitely need a transistor to drive the LEDs 'cos they need to be bright mothers and also you'll probably want to drive the indicators on the dashboard to let you know they are flashing. And, if you want to get real fancy you can also hook up a small piezo speaker to make the "bokka bokka" sounds when you indicate.

It's not all so trivial now, to do it properly, eh?

seeyuzz
river

[wagonist]

Anyone with some real knowledge about electronics fell free to shoot this theory down:

If all it requires to get the load right is to insert a resistor in parallel or series, couldn't you simply install a potentiometer temporarily, tweak the dial until it flashes at the correct rate & then measure the resistance across the pot to find out what resistor is required?

Alternatively, you could've just gone down to the auto accessory shop & bought the replacement led fitment as these will already have the resistor built in.

[river]

Hi,

If the bokka requires a certain load for it to flash properly then it can be done. But, you also need to have current limiting resistors for the LEDs. If you have enough load on the bokka for it to function properly, will the resistance be enough for the LEDs? Will the LEDs be under or over driven? Does anyone know what load the bokka needs to function properly?

I thought the LED lights you could buy for your car were more for brake and parking lights, rather than indicator bulb replacements? That is, the internal resistor in the LED unit was to limit the current and allow it to work from 12V, as opposed to providing adequate resistance to match the bokka for indicator purposes.

seeyuzz
river

[wilbo666]

The load resistance will need to be quite sizable!

From memory indicators are 21W (or 5W for the side ones?)...leds assume the LED draws 1W...we either need 20W (or 4W)...

A 20W resistor is generally pretty huge! (heck even a 5W resistor aint small)....


(crap image stolen from jaycar )

While it should work it isn't exaclty elegant...

Anyone with some real knowledge about electronics fell free to shoot this theory down:

If all it requires to get the load right is to insert a resistor in parallel or series, couldn't you simply install a potentiometer temporarily, tweak the dial until it flashes at the correct rate & then measure the resistance across the pot to find out what resistor is required?

Most general potentiometers don't have huge power ratings...20W is more than likely to let the smoke out of most of them.

The required resitor values could be worked out easily enought at any rate if one wished....

Cheers
Wilbo

[The Witzl]

a 555 timer circuit would be the best option... and river is correct, you would need output transistors to carry the full current load, or some transistor controlled relays (when you add up all the indicators and the dash lights it would be more than a TO-92 or TO-220 package could handle most likely).

One point to note here, however, is that LED indicators are actually illegal to use on the street - ADRs prohibit their use. I should know, I import the damn things.

Would be a fun project still, so why not give it a go anyway? The parts are worth next to nicks.

[The Witzl]

River is correct, your standard pot can only handle 0.25-0.5watts before they smoke in a nasty way.

The resistor method is far from elegant, and poo.