R.I. Duallys self-made modulator

[craque]

Hi all,

I just lost my entire essay-of-a-post by accidentally closing the tab; one of the reasons I'm not a forum dweller. I'll try again.

I bought a pair of Rigid Industries Duallys back in November 2013 for my '87 BMW K100LT. My primary reason was because at that time we were suffering many bouts of heavy fog and on a few occasions I had to drive on unlit country roads in pitch black. I felt like the BMW lights weren't really cutting it for me.

The lights I received are fantastic, of course I bought them from BikeVis otherwise I wouldn't be posting here! I hooked them up and they looked fantastic, I went ahead and attached them to my motorbike. They couldn't look more well-suited if they tried!

I'm writing here because I produced a modulator for them. I was considering buying some more DRLs to increase my visibility as well as having these ultra-bright spotlights that I can't keep on all the time, but it seemed a bit silly adding more lights to the bike. My modulator consists primarily of a L7805, a 555, and a MOSFET. It takes in 4 wires: Ground, dipped beam (for modulating the spotlights), full beam (constant on for spotlights), and the forth for sinking the load of the spotlights (since they're wired in high-side for the simplicity of the MOSFET configuration). The dipped and full beam wires actually operate the modulator with use of 2 diodes. The astable configuration of the 555 uses 330KΩ and 1.5KΩ for R1 and R2, and 0.047μF for C. This enables me to achieve a 99.55% duty cycle at 92Hz. Because the 555 isn't able to go lower than 51% duty cycle, I simply inverted the signal to achieve a final output of 0.45% duty cycle.

The unfortunate thing is that they are actually still too bright for my liking, but I comfort myself with the fact most other motorists drive around with dipped beams brighter than my modulated spotlights. I say that because I can't actually make them any dimmer! The constant current circuits built into the spotlights start to mess up when pulsing 12VDC any less than 45 microseconds (the result of 0.045% duty cycle at 92Hz is actually 49 microseconds). I could maintain the on-time of 49 microseconds and increase the off-time therefore lowering the frequency, but I'd rather not give the driver ahead a photosensitive seizure. The constant current circuitry can't handle the short Voltage bursts and start to boost the output by missing pulses and eventually lowering the frequency regardless of the 555.

I really do care about other motorists, I stop many times along side the road and walk several yards and see the effects of the spotlights, I move up and down, side to side to really get an idea of light distribution and to get an idea of how other motorists see me and my lights.

Anyway, I'm more or less happy with the outcome. They're connected to my dipped and full beam. I have them on a separate switch should I ever want to turn them off completely.

This is my first electronic circuit used for an actual project of mine, so it's on veroboard for now:

... and yes, I didn't think about plotting component locations, ha. The L7805 and MOSFET don't require a heatsink because they operate cool when used this way, there's no heat produced at all.


IC1 = L7805 regulator. IC2 = 555. T1 pauses the 555 trigger for full beam (I know, could have been done better, but it works and it's already made now). T2 works to invert the signal generated by the 555 and saturates T3, the MOSFET. D1 and D2 serve to power the circuit without sending power back to the other headlamp filaments but still used to change the modulator mode. Some resistors thrown in for shits and giggles. I should probably sleep now.

I will post some more images later when the bike is together again!

Pleasant regards,
J. W.

[Fluke]

Hi

Thanks so much for your post, and gutted for you that you had to start over.... I hate computers sometimes!!!!

Yeah it's a real problem trying to dim constant current driven LEDs... but a great solution and nice little circuit!.

Are you going to pot it up for permanent install ?, looking forward to the finished results.

ps: I like the high beam disable function and the inverted 555 output is cunning :) (at least for my puny brain)

[craque]

That's fine! I don't have much in the way of telling people about the things I make, so I enjoy it.

It won't be a permanent install just yet. This bike is very much my love, but maybe I'll start on it again in the future and make it more permanent and professional.

The constant current drivers in the Duallys aren't too problematic, it just means the output isn't how I'd like it. Also, I didn't mention that when testing shorter 12VDC bursts, the output changed when the engine was started (from the spotlights, not my circuit) but I guess that's to do with the voltage changes in the system.

The wiring I have so far is non-invasive to the bike's harness, it just piggybacks the connections from the H4 bulb socket (not to power the lights, just the controller).


I need to waterproof the controller box properly, attach it somewhere out of view. Reduce the length of wires because all my testing is over, solder up and heat shrink all the connections. Simply add in the switch to the circuit, I'm certain adding it in-line between the battery and spotlights should be fine (because it's a high-side load meaning it's always live).


BMW dealers sold me a switch for £30! Madness. I chose to go for the fog light icon. There is a momentary push mode (when you push the switch upwards). Not sure what I could use that for, so it's unused at the moment.

I'll get to the end result pictures eventually!

Update: Well, I spent a good few hours taking out all the lengths of wire I didn't need. I'm still piggy backing the H4 socket, I don't want to cut into the harness. It's all nice and neat, and the switch is wired in.

All that's left to do is waterproof the controller box (wired in using spade connectors, so I can just take it out and waterproof it another time). Also, secure some wires and the controller box to the frame so it's not just hanging by the wire. Lastly, to put all my panels and bits back so that everything is concealed again.

Update: The controller box has been waterproofed with a fine layer of silicon glue. Wires and box have been secured. All the bike panels and such have been put back together.

Only one problem to be had: As I was driving once in the evening in heavy traffic, I noticed that my headlight wasn't on, but the spotlights were. People were flashing me even though I had just the spotlights on. Where I was piggy backing the H4 socket, the socket actually disconnected from the back of the headlight bulb. It's been put back on, and I'll see if it continues to be a problem. This was 3 or 4 days ago, hasn't happened yet after about 150 miles of driving. It could have just been from when I secured the wire and the box, I may have loosened the connector during that time only. Now, after installation I've secured the plug again, it shouldn't come out.

[Fluke]

Thanks for the update. Looking great!

A £30 switch!!... quite some mark up then :(. Looks neat though

Trying to think what you could use the momentary push for, but I think you have all functions covered

Regards

[craque]

Well... I've been meaning to get some shots of what the K100LT looks like with the Duallys spotlights attached at night so I've used my helmet camera to capture a bit of it.

Here are some shots in GIF form because the video is super long and I have nothing to edit it with. Hope they load ok for everybody.

Spotlights completely on:


Spotlights completely off:


Comparison (doesn't really do it any justice to be honest):

Due to the nature of my fish-eye lens, it makes distance-related demonstrations a bit moot, but it lights up those trees really well and will blind someone very easily at practically any distance.

Completely on (just after installation):


With my PWM controller (which is hard to demonstrate in picture; that's dipped beam):


I'll see if I can capture a bit more of it in a dimmed PWM mode since that's what this thread was meant to be about. Unfortunately I've just been so busy these few months and my attention has been drawn to other things, but I haven't forgotten!

Pleasant regards,
J. W.

[Fluke]

Hi

Thanks for taking the time with the gifs and photos... I think the results are amazing!!. Glad they still going strong!

These add a seriously large 'layer' of safety to your BMW.

Regards