# Need help with I hope simple project!

Discussion in 'General Electronics Discussion' started by Tom Stark, Jun 16, 2014.

1. ### Tom Stark

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Jun 15, 2014
OK, here is the deal. I am a machinist and fabricator, and have built some electronics, but am far better with machining. I need to build what I think will be a simple circuit for my motorcycle. I have an LED headlight that has 2 wires and 3 functions, high beam, low beam, and flashing. Each time the unit is powered on it goes to the next operation. So if I have the light flashing, turn the bike off, turn it back on it will be on high, then next time low, then back to flashing.
During the daytime it is hard to tell which mode it is in unless I get off the bike and look. So what I want to do is build a circuit that will light 1 of 3 LED's in the same manner. When tied together I can label the LED's so from the seat I can tell what mode the light is in. This would be most helpful to me. So the circuit would be grounded 100% of the time, and would see 12 volts only when the LED headlight sees 12 volts. I have no issue using low voltage LED's and resisting the 12 volts so they don't burn out.
OK, anyone have any idea how to do this? I would hope it would be easy, but really don't know! (that is why I am here!)
Thanks in advance! Any help greatly appreciated!
Tom

2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
The simple solution is simple. (well, if you want a single LED to be either bright, dim, or flashing) If you want one LED for bright, and another for dim, and another for flashing, that will be much harder.

The simple solution first:

You get a high brightness red LED and place it across one of the existing white LEDs with its own series resistor. This will divert a small amount of power from the white LED to the red LED.

If you assume there's 4V across the white LED (you would actually measure it) and that the forward voltage for the red LED was about 2.1V at 20mA (the specs for the LED would tell you this) then the resistor in series with the red LED would be (4 - 2.1)/0.02 = 95 ohms (you would use 100 ohms.

You would also need t ensure that the red LED was oriented correctly because they only work one way around.

This simple solution might work during the day, however at night the red LED would be blinding.

An ideal solution would dim the LED as the ambient light changes.

For that a more complex circuit is required.

3 LED issues:

Your light almost certainly operates in the following manner. For "high beam" the LEDs are constantly on. FOr "low beam" the LEDs are turned on and off very frequently (perhaps hundreds of times per second) so that they are off perhaps 75 percent of the time. The switching is so fast you perceive them to be continually on but at the average intensity (so 1/4 intensity) For flashing, this same on/off cycle is used, however the frequenct is reduces to something between probably 1 and 3 Hz. Maybe it even flashes SOS.

It is non-trivial to detect which mode the light s in. It certainly can be done, but not with just a few passive components.

Are you familiar with microcontrollers?

3. ### Tom Stark

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Jun 15, 2014
I can follow directions, and have assembled ECU's to run fuel injection and ignition on my car. Just to be clear, here is a link to the head light I am using, http://www.ebay.com/itm/Motorcycle-...Parts_Accessories&hash=item27e3ac39af&vxp=mtr
I was hoping I could have 3 LED's on the dash (I have yet to make the dash out of aluminum bar stock, THAT is where I shine, welding, cutting, machining, etc), but if I need to have just one LED and have it bright, low or flashing, that is cool too. Actually, really if I can just tell when the headlight is flashing that is what I really need. At night when I want the light on solid I can see if it is high or low beam, but in bright day light, I want to know if it is flashing. It is easy to lose track, because when you turn the bike on, it goes one mode, and when you hit the starter, it turns the light off, then back on when you release the starter button, and if the bike stalls, yeah, a change again. Flash your lights to signal a semi truck, and OK, wait, was I flashing, high or low? Gets confusing REAL fast. Maybe it would be easier to put a photo cell by the head light and use that somehow to detect flashing? On surface streets I can get stopped at a light behind a car and see, but on the freeway, yeah, hard to tell!
I really appreciate your help on this! Thanks!
Tom

4. ### Damian Mitchell

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Jun 5, 2014
Assuming the LED controller is changing the duty cycle of the pulses for high and low modes, this circuit might be helpful? http://www.edn.com/design/analog/4347834/Circuit-converts-pulse-width-to-voltage

The one normal (red?) LED - Bright/Dim for high/low (or 2 LED's with the help of some Zener Diodes and another Op amp)

Flashing - Just wire a diode to one of the Power LEDs, with the appropriate resistor as a flashing indicator...

5. ### chopnhack

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Apr 28, 2014
Tom, I won't be able to provide much help, but a question came up: How do you currently change the mode? It would seem terribly inconvenient to have to turn off the bike to change the mode. Perhaps in addition to the status light project maybe you can wire up a 4 position? switch: Off, + each mode - would seem to be real convenient that way. Seems like the light was manufactured with cost in mind as they omitted the switch and the extra wiring that might have been required. Best of wishes and welcome to a fantastic forum!

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6. ### Tom Stark

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Jun 15, 2014
LOL! Forgive me, I was trying to not provide too much info, just explain the problem. I have the LED wired to the high beam switch. If I switch to low beam, the LED is off, switch back to high beam and it is on in the next mode in the rotation. On my ride home today, (over 300 miles) on the freeway I realized I was not sure what mode I was in. Had a hell of a time figuring it out! LOL! Don't like to stop! In 300 miles I made 2 stops for fuel, (for the bike and for me!). In reality, on the freeway the mode I am in does not really matter. It is more important on surface streets where traffic is going in all directions. I need to be as visible as possible. On the freeway, we are all going the same way, no cross traffic, no one pulling out of parking lots etc. But I am a little (did I really say LITTLE?) OCD, so yeah I need to do something!
Thanks for your welcome! And Yeah, this is a great forum, I am sure I will learn a lot here! Hey, if any of you have machining, engine building, or fabricating questions, let me know so I can help you!
Thanks!
tom

7. ### Tom Stark

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Jun 15, 2014
I took a quick look at the link you provided, and if I can figure out how to get to the voltage supplied directly to the LED, I think that may be helpful. Will have to give it a better look when I have more time and am not so tired. Rode over 700 miles between yesterday and today! Now that is some riding! When I was young I did do that in a day, but that was 30 some years ago, so,... LOL! (I choose to think I am smarter now, not older!)
tom

8. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
I have a similar configuration for the headlight of my bike. I just stick my hand in front of the headlight to see what it's doing.

9. ### davennModerator

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Sep 5, 2009

ahhh the Spanish method ... el manual way

D

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10. ### KrisBlueNZSadly passed away in 2015

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Nov 28, 2011
Yeah... I was going to suggest adding a bit of shiny metal in front of the headlight as a reflector, but I thought "that's too obvious..."

11. ### Tom Stark

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Jun 15, 2014
LOL! Mine if a 77 GL1000 Honda Goldwing, with full Vetter gear. I can't reach within 2 feet of the head light when I am on the bike. That would be the easiest solution! I may buy another headlight, to dissect and see if I can't use it for what I want, firing a MUCH lower brightness LED. It is only \$20 so worst case is I lose \$20 and that is not bad!
Tom

12. ### KrisBlueNZSadly passed away in 2015

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Nov 28, 2011
If you do get another headlight and take it apart, feel free to post photos here. We may be able to suggest a way to hack into it to determine which mode it's in, or change it so you can set the mode with an external switch.

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13. ### Tom Stark

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Jun 15, 2014
I surely will! That would be great. Will be a little bit before I do that, have a few "priorities" just crashed in on me! LOL! (isn't that the way it goes!) Again, the help here is
GREATLY appreciated! You guys are the best!
Tom

14. ### BR-549

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Jun 20, 2014
Can you get a schematic of the bike? With the original light, were there 2 filaments in the bulb? Or one filament and a resistance was added to dim bulb? In other words....how is the hi-lo beam switch doing what it does? Is it switching between 2 voltages? Or is it adding resistance? Also, please confirm that one of the wires on the new light is ground. Can you live without the blinking? There might be an easy way to put your bike back in spec.

15. ### Tom Stark

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Jun 15, 2014
It is 2 filaments, so the way I have it now is hooked up to the high beam, so if I switch to low it shuts the head light off. Right now I have a few other things that popped up I need to address. 14 hours before I was to take a 700 mile ride, I broke the drive shaft! took 5 hours to replace. Now I need to design and build a fixture to rebuild these drive shafts as the one that replaced mine is also 35 years old! And a few other things popped up!
When you hit the starter it turns off the head light. I will look at the wiring diagram and disable that so the headlight stays on. Then at least I can turn the bike on before I get on, and see what mode the headlight is in, and not have to worry if I stall the bike as to what mode it changed to.
Tom

16. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
Ummmm, if it's a LED, how does it have any filaments at all?

17. ### Tom Stark

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Jun 15, 2014
Sorry, the ORIGINAL light had filaments. This is a 77 bike. The question was regarding a wiring diagram for the bike, so I answered the original configuration. The rest of the details are above. Simply put, original light was a sealed beam. Along the way some years after original production it got an H4 halogen, I switched to a 2 wire LED with 3 modes. When you type it all out, seems a lot more than really is! LOL! Sorry, tried to keep things simple.
Tom

18. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
No problems. I just wanted to be sure we were talking about the same thing

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19. ### Tom Stark

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Jun 15, 2014
I understand! I am always "I don't know what you mean, only what you say" I am pretty good with electrical issues, after all, "way of least resistance" and "makes a complete circuit" How many times have you heard people "Oh, this or that problem, CLEARLY a short circuit" when it is actually an open. I can relate! LOL!
Tom