Electrical question re: LEDs

[willie]

I was planning on replacing the signals on my bike with 12 volt LED units. I unplugged the signal and plugged in the LED wires. I was surprised and disappointed that it won't flash. Can anyone explain why and what I have to do to make it work? I figure that the reduced current draw is the culprit. The LED unit draw is minimal. IF thats the reason will adding a resistor do the trick?
Thanks again.
Willie in TN

 

[TheCafeKid]

On alot of the LED signals you have to install a load balancer. Or someone was telling me about a flasher unit that doesnt look for load to flash. Dunno wich part is cheaper..

 

[davewallen]

For a resistor to work you would need it to be parallel to the LED, and it would need to be a pretty low value. I'm guessing a normal signal at 12 watts, which would be one amp at 12 V, which would be (oddly enough) a 12 ohm resistor. (of course, it's been 30 years since I did any electrical work) By the way, it would also need to be a 12 watt resistor - not your normal 1/8 watt types.

You would probably be better off using a flashing LED, though.

 

[drhach]

You don't necessarily need a load bablancer. Try using a solid-state flasher. Normally they are mechanical. Specifically, they rely on the heat created from the current to collapse a metal bar in the flasher unit. When the bar collapses from the heat, it touches a contact and closes the circuit. When it cools enough, it springs open and in turn opens the circuit back up. I may have the theory reversed but basically that is what normally happens. LEDs don't allow enough current to travel through the system to create the necessary heat. A solid state flasher just has a timed switch that opens and closes the circuit. Nothing mechanical. It should drive everything just fine.

 

[willie]

Thanks! I did a Google search for LED load balancers after reading the Kid's post and uncovered a post on another board that had exactly the info I needed including a schematic. Looks like a 10-12 ohm 10-12 watt resistor will do the trick and for not much $$ at all. Next step is to figure out how I can make several LED units flash sequentially. I've looked into available kits that might do the trick in that dept. Should be cool if I can make it all happen the way I hope.

 

[Steve]

Is your intent to add some cool-looking lights, or are you trying to reduce your electrical useage? :-s

If you are trying to spare some electrons, adding a load resistor is going to put you right back where you were, as far as current consumption, so there is no gain.

If you don't mind spending about $10-15, just go to Auto Zone or whatever you have handy, and get an electronic flasher. As drhach mentioned, they have a timer inside, so they flash at the same rate, regardless of the load.

As far as the sequencing...you will need to do some electronics work there. There will be cascading timers involved, which are very possible, but making them small is the trick.


.

 

[Redman]

If your intent in going to the LED lights is to reduced current draw, then adding the load balancer or the resistor will defeat that purpose by just drawing more current somewhere else.

Oh, Hi Willie.

 

[willie]

Understood, good buddy. My only intent was to modernize the appearance of the bags. Just trying to be a little different.
Willie in TN

 

[davewallen]

Thanks! I did a Google search for LED load balancers after reading the Kid's post and uncovered a post on another board that had exactly the info I needed including a schematic. Looks like a 10-12 ohm 10-12 watt resistor will do the trick and for not much $$ at all.

D^mn, I was right! (look of shock, as I pat self on back)

Can you give a link to that other site, in case this comes up again?

 

[willie]

http://www.jockeyjournal.com/forum/showthread.php?t=26078&highlight=LEDs
You'll see why I was so impressed.
Willie in TN

 

[bakalorz]

Is your intent to add some cool-looking lights, or are you trying to reduce your electrical useage? :-s

If you are trying to spare some electrons, adding a load resistor is going to put you right back where you were, as far as current consumption, so there is no gain.

If you don't mind spending about $10-15, just go to Auto Zone or whatever you have handy, and get an electronic flasher. As drhach mentioned, they have a timer inside, so they flash at the same rate, regardless of the load.

As far as the sequencing...you will need to do some electronics work there. There will be cascading timers involved, which are very possible, but making them small is the trick.

What he said ... but timers etc is the old primitive way.
The right way to do it now is with a microprocessor.

ANY (and I litterally mean any) flash pattern or sequence you want, as many leds as you want doing whatever you want them to. And in a lot of ways actually easier than discrete timers and such.
Also much easier to make changes and adjust after its built.

And physically small if you want it to be.
The processor that controls it all is one chip, and pretty much the only other components you need is a mosfet and resistor for each output/led.

As far as LEDs go, I got some of the replacement 1156/7 bulbs, and none of them were really bright enough. What is good are the LED assemblys they make for trucks.
Like these http://cgi.ebay.com/ebaymotors/PIRA...022QQitemZ350002441825QQrdZ1QQsspagenameZWDVW

Those are pharking bright ...

I am going to replace all my tail and turn lights with LEDs, and earlier tonight was playing around with them, seeing what they looked like if you strobed them.

 

[Steve]

What he said ... but timers etc is the old primitive way.
The right way to do it now is with a microprocessor.

Yeah, you and I know that the microprocessor is just a fancy, updated timer (in this application), but I was just trying to keep it in easy-to-understand terms. 8-[

If you get down to it, the standard bi-metallic strip in a standard flasher is a type of timer, too, but has a duty cycle based on load. The microprocessor-controlled units are based on time, not load.

There is still an advantage to the bi-metallic flasher, though. When a turn signal is not working, you will know it, because they will not flash on that side. With an electronic unit, your indicator on the gauge panel will still flash, even if both signals (front and rear) are burned out.

All the more reason to do your T-CLOCK inspection before every ride. :shock:


.

 

[Planecrazy]

There is still an advantage to the bi-metallic flasher, though. When a turn signal is not working, you will know it, because they will not flash on that side. With an electronic unit, your indicator on the gauge panel will still flash, even if both signals (front and rear) are burned out.

...Of course the flipside to this is that if you convert to LED's than the likelihood of a "bulb" failure is rather remote. After all, most modern LED's have a service life of 11 YEARS or so left on continuously! That's pretty darn reliable when you think about it.

Still, I agree with you that one should always do the "walkaround" before taking off into the wild blue yonder!

Regards,

 

[Steve]

... if you convert to LED's than the likelihood of a "bulb" failure is rather remote.

True enough, but "bulb" failure is not the only reason signals don't work. Evidently you have been lucky enough to not ever had any corroded connections. :shock:

Nah, I know better than that. 8-[


.

 

[Planecrazy]

True enough, but "bulb" failure is not the only reason signals don't work. Evidently you have been lucky enough to not ever had any corroded connections. :shock:

Nah, I know better than that. 8-[


.

Hah!!! ... Yes, you do! :lol:;-)

I've been pretty lucky overall, though ("knock on fake wood" - as he taps his own skull)!

Regards,

 

[bakalorz]

What he said ... but timers etc is the old primitive way.
The right way to do it now is with a microprocessor.

ANY (and I litterally mean any) flash pattern or sequence you want, as many leds as you want doing whatever you want them to. And in a lot of ways actually easier than discrete timers and such.
Also much easier to make changes and adjust after its built.

And physically small if you want it to be.
The processor that controls it all is one chip, and pretty much the only other components you need is a mosfet and resistor for each output/led.

As far as LEDs go, I got some of the replacement 1156/7 bulbs, and none of them were really bright enough. What is good are the LED assemblys they make for trucks.
Like these http://cgi.ebay.com/ebaymotors/PIRA...022QQitemZ350002441825QQrdZ1QQsspagenameZWDVW

Those are pharking bright ...

I am going to replace all my tail and turn lights with LEDs, and earlier tonight was playing around with them, seeing what they looked like if you strobed them.

Yeah, you and I know that the microprocessor is just a fancy, updated timer (in this application), but I was just trying to keep it in easy-to-understand terms. 8-[

If you get down to it, the standard bi-metallic strip in a standard flasher is a type of timer, too, but has a duty cycle based on load. The microprocessor-controlled units are based on time, not load.

There is still an advantage to the bi-metallic flasher, though. When a turn signal is not working, you will know it, because they will not flash on that side. With an electronic unit, your indicator on the gauge panel will still flash, even if both signals (front and rear) are burned out.

All the more reason to do your T-CLOCK inspection before every ride. :shock:
.

I wasn't very clear. I only meant to say to use a microprocessor in the case of the sequenced/multipatterned LED thingy that the OP wants to do.
So the microprocessor would be replacing a bunch of timers or gates etc. in some kind of frankenstein sequencing circuit.
For "plain" LEDs not flashing in any pattern or with weird timings, I would be lazy and just use a commercial heavy duty flasher (i.e. the load independent ones)

Also, the bimetalic strip type gives a warning with OEM lights, but it gives you no useful warning with the LEDs. You can't use a bi-metalic flasher with the LEDs unless you are using the extra load resistors. In that case, it won't warn you if the LED burns out or the connection to the LED corrodes. It will warn you if your load resistor burns out, or the connection to your resistor corrodes.

However, despite what I wrote in the first para of this post; if you want a warning of non-functioning LED indicators, the microprocessor is probably the easiest way to do it.
The microprocessor I'm going to use for my flasher has an A/D converter built in ... so its actually very easy to sense the current across the FETs.
You can set a warning in the software for any current you want, even the very low LED current without load resistors.

I consider that unlikely enough that I probably won't bother with it, but do plan to have it notice if I forget to cancel my turn signal. I will have it cancel the signal, but flash the dashboard indicator fast to remind me that I goofed ... so that I hopefully eventually remember.

 

[willie]

Martin, you posted: "The right way to do it now is with a microprocessor.
ANY (and I litterally mean any) flash pattern or sequence you want, as many leds as you want doing whatever you want them to. And in a lot of ways actually easier than discrete timers and such. Also much easier to make changes and adjust after its built. And physically small if you want it to be.
The processor that controls it all is one chip, and pretty much the only other components you need is a mosfet and resistor for each output/led."
I hate to sound more ignorant than I am but what microprocessor will I need that will enable me to sequentially light numerous (4 max) LED units? AND, where can I get one?
I may've opened a can of worms here but its worth my asking for the info that may enable me to accomplish my original goal.
Willie in TN

 

[QuaiChangKane]

Most LED tail light integrators for newer sportbikes come with 20w, 5ohm in-line ceramic resistors for the turnsignals.

You can pick them up for less than a buck a piece at Radio Shack.


Solder them in-line on the hot wire, and you're good to go. LED's just don't draw enough current to trip your flasher - you'll need a resistor inline for each turn signal, if you convert both front and rear.


ALSO - smaller "stick-on" type flushmount incandescent signals do the same thing. If you don't swap out your flasher or install in-line resistors, the bulb will stay on and melt the housing, a real potential for an electrical fire.


(Sorry for the overexposed picture - I was in a hurry. The P/N is "RX27", but not sure of the brand.)

-Q!

 

[bakalorz]

Martin, you posted: "The right way to do it now is with a microprocessor.
ANY (and I litterally mean any) flash pattern or sequence you want, as many leds as you want doing whatever you want them to. And in a lot of ways actually easier than discrete timers and such. Also much easier to make changes and adjust after its built. And physically small if you want it to be.
The processor that controls it all is one chip, and pretty much the only other components you need is a mosfet and resistor for each output/led."
I hate to sound more ignorant than I am but what microprocessor will I need that will enable me to sequentially light numerous (4 max) LED units? AND, where can I get one?
I may've opened a can of worms here but its worth my asking for the info that may enable me to accomplish my original goal.
Willie in TN

Pretty much any of the microcontrollers that are available would work for this. I have been building stuff using the microchip.com PIC series, so I personally would use one of those because I'm familiar with them. The one I would use is the PIC16HV785. The HV means it has a built in regulator, so it saves using a seperate regulator chip to make a 5 volt supply from the bikes 12-14 volts.

In addition to the micro, you would need a P-channel mosfet for each LED or group of LEDS (if multiple LEDs turn on and off together they only need one mosfet for the group)

You do have to program the micro, but it sounds like what you want to do is very similar in some ways to what I am doing with my turn signals, so I could help you with that if it is as similar.

this is microchips page for that processor,
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1335&dDocName=en025830

This is the datasheet from that page
http://ww1.microchip.com/downloads/en/DeviceDoc/41249D.pdf
The datasheet is huge, but 90% of it doesn't apply to what you want to do. The stuff for timers, CCP, comparator, volt ref, opamp, A/D converter, PWM, EEPROM, can all be ignored.
The only thing you would need to know is the stuff for I/O ports.

If you search around on their site, you can find their free simulator, called MPLAB. Included in the help for the simulator is a tutorial that teaches you how to use one of their micro's to turn a LED on and off.

 

[Jaguarjoe]

Most LED tail light integrators for newer sportbikes come with 20w, 5ohm in-line ceramic resistors for the turnsignals.

You can pick them up for less than a buck a piece at Radio Shack.


Solder them in-line on the hot wire, and you're good to go. LED's just don't draw enough current to trip your flasher - you'll need a resistor inline for each turn signal, if you convert both front and rear.


ALSO - smaller "stick-on" type flushmount incandescent signals do the same thing. If you don't swap out your flasher or install in-line resistors, the bulb will stay on and melt the housing, a real potential for an electrical fire.


(Sorry for the overexposed picture - I was in a hurry. The P/N is "RX27", but not sure of the brand.)

-Q!

Those dummy load resistors must be placed in parallel (or across) the LED light to work. Putting them in line will not work. Th object here is to consume current. Placing them in line will only allow the LED to limit current in the circuit- usually about 20 ma. or so. Placing them in parallel will cause it to draw 2+ amps if they're 5 ohms- more than enough to satisfy the flasher.

LED's do not generate enough heat to melt anything. You could keep them on for 11 years and nothing would come close to melting.