Headlights/Tail lights - other power source

[El Rojo]

I wired up the headlight circuit last night. I will work on a schematic and post later along with pics of the car itself.

What I ended up using was this:

A 3v lithium button cell wired to an NPN transitor through the collector and emitter, the base is wired to the "forward" tab on the bit board for the headlights (2 white leds). I used a 470 ohm resistor in line on the transistor base and a 330 ohm resistor on the Leds. Leds are very bright using the lithium cell. for the brake lights, it's basically the same setup, with the transistor base wired to the "reverse" tab on the bit board.

Wired like this, the headlights come on when going forward and the brake lights come on in reverse. I plan on modifying the circuit so that the brake lights are on, but dimmed in forward and get brighter in reverse.

El Rojo

[Gent]

Thanks for all the info everyone. Where are you guys getting your LEDs? I picked some up at Radio Shack, but unless you buy the variety pack, they don't have the really small LEDs, and I couldn't find any small white or blue lights there either.
Thanks.

[hbarer]

www.eled.com
www.allelectronics.com

[Gent]

Thanks for the links.

[El Rojo]

There are a variety of online suppliers of leds.

www.newark.com
www.mouser.com
www.allelectronics.com

Give any of these a try.

El Rojo

[El Rojo]

Well, I was intrigued by mjb's talk of a voltage diode, and sure enough, there's one on the bit board. Although the transistor set-up worked fine, I wasn't too happy about having that extra lithium cell on-board (kind of like driving arouund with a trunk full of cement...). Anyway, I broke out the digital meter, and sure enough, I could pull over 3.0 v off of the diode. So now, the setup will go like this:

Headlights (2x3mm ultrabright 3mm led) are wired hot to the diode, and grounded to the backup lead on the bit board, now I know what you are thinking, why in the @#$$ did he use the backup lead if the headlights are supposed to come on when going forward, well the answer is, the backup lead switches to ground (0v)when going forward only, this completes the circuit and you get nice bright white headlights only when going forward. I found that if you use the ground from the right side of the bit pcb, not only do you have lights that stay on all of time, you can only pull close to 2v, wierd huh?

The tailights are currently wired hot in the same way, but use the forward lead for ground when going backward. This produced an odd effect, if the wheels are impeded when going forward, as the wheels slow down, the brakelights get gradually brighter, so it looks like your little bit driver is riding the brake, which is much more entertaining than the carpet fuzz snagged around the axle that is the real culprit.

I'm actually thinking of wiring the brake leds hot to a lower voltage, as pulling much current from the diode has adverse affects (like overall voltage drop across the circuit).

I hope to post photos next week.

El Rojo

[Gent]

Rojo,

Your mod sounds really sweet, can't wait to see the pics so I can try something similar.

[Spanky]

since im clueless at this can someone pick a site, any one and then give me a rundown of the correct led's and everythign that i would need from that site to do a headlight mod.. i only want to do headlights... and if possible i want to have 4 beams...(led's) i have looked on the previously listed sites, but see many different led's for each color all of which have different specs. i dont know what they mean and dont want to buy the wrong thing. also if i need resistors. which ones will i need. i havent auctually seen a basic shopping list of what you need to do a light mod in any of the posts.. anyway i think it would be very helpful.

[ffctp]

Originally posted by El Rojo
Headlights (2x3mm ultrabright 3mm led) are wired hot to the diode, and grounded to the backup lead on the bit board, now I know what you are thinking, why in the @#$$ did he use the backup lead if the headlights are supposed to come on when going forward, well the answer is, the backup lead switches to ground (0v)when going forward only, this completes the circuit and you get nice bright white headlights only when going forward.

El Rojo: I tried doing the same thing with a Bensu clone, which may itself be the problem, but for whatever reason, wiring the LED to the diode and either forward/back lead causes the LED to light up regardless of direction. For both leads, any forward or back movement will light it up. This seems odd, and is frustrating because this would seem to be the best solution.
I could just do a separate battery, but like you said, it's extra weight. Since I'm supposed to race a friend monday, I want to out-floss him with my lights *and* win the race. Hmmmm.
Having both sets of lights come on (or possibly just going with headlights for now) when moving at all isn't so bad, but it kind of defeats the point of brake lights. I'll keep trying to figure this out.

[ffctp]

Hmm, also running the led to diode/left or right lead causes the led to be dimly lit at all times and brightly lit only when turning the appropriate direction. Maybe I should try these resistors again and see what happens.