Electrical question re: LEDs

[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/PIRAN...spagenameZWDVW

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.

[8trackmind]

You guys are doing way too much thinking for such a simple project.
The flasher is the whole problem and it's easy to fix.
My 550 runs all Leds with no resistors and a modded three terminal electronic flasher available at any auto parts store.

Read this. http://www.mesa4x4.com/tech_articles...r/flasher.html

[QuaiChangKane]

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.

You're right, what do I know from installing them per the mfr's directions?

If you wire them in-line, they trip the flasher.

And the second part was about incandescent bulbs melting their housing...


-Q!

[doug g]

I always thought that as you added more resistors in parallel then you total resistance value would drop.
example:
R1 X R2/R1+R2

If I had 4 100 ohm resistors in parallel then the total resistance would be 25 ohms based off of my calculations. So therefor why would I wire the resistor in parallel with the LEDs as this would only lower my overall resistance.

[Steve]

I always thought that as you added more resistors in parallel then you total resistance value would drop.
example:
R1 X R2/R1+R2

If I had 4 100 ohm resistors in parallel then the total resistance would be 25 ohms based off of my calculations. So therefor why would I wire the resistor in parallel with the LEDs as this would only lower my overall resistance.

You are quite correct. \\/

Why would you want to do the resisitor in parallel? Why not?

Have you measured the resisitance of an LED? No, I hadn't either, until writing this, so let's do the math...14 volts, only 30mA, is equivalent to about 525 ohms. Putting a 25-ohm resistor in parallel with that, and using the formula, equals 23.86 ohms, meaning it will allow just over half an amp to flow. Not enough to trigger the thermal flashers, but you get the idea. If you use a 10-ohm resistor, the resulting parallel circuit will be 9.8 ohms, which will allow just about 1.4 amps. Might trigger some of the most sensitive thermals. Using a 5-ohm resistor, circuit is 4.95 ohms, allowing 2.8 amps, which is close to what one incandescent bulb draws. Again, might trigger some of the sensitive ones, but...

If you put the resistor in series with the LED, you will have about 550 ohms equivalent, which will only allow 25mA, meaning the LED will not be as bright as it should be, and, by drawing even less current, it's even less likely to trigger a thermal flasher.

In other words, why go to the power-saving benefits of LED lighting and then have to provide an alternate path so you end up using the same amount of power anyway? :shock:


.

[Planecrazy]

In other words, why go to the power-saving benefits of LED lighting and then have to provide an alternate path so you end up using the same amount of power anyway? :shock:

The simple answer is "so that you have a more reliable light source and don't have to worry about burnouts."

BUT

I'd much rather upgrade to an electronic flasher so that I COULD take advantage of the lower voltage/amperage benefits of LED ... that leaves more available power (from our already weak charging systems) for all the extra "doodads" I've got running on the bike, like the stereo, the GPS, the digital clock/voltmeter/thermometer, etc.

Regards,

[Steve]

That was pretty much my point, too. With all the calculations and then trial-and-error involved in getting the correct resistors, then finding a place to connect and mount them, why not just get a new flasher and be done with it?


.

[Planecrazy]

That was pretty much my point, too. With all the calculations and then trial-and-error involved in getting the correct resistors, then finding a place to connect and mount them, why not just get a new flasher and be done with it?

I kind of figured we were thinking the same thing ... but for somebody who might have misinterpreted your post I figured I'd post "the answer," hehe!

Regards,