Wiring up a generic brake light. [SOLVED]

[slaphappygamer]

Some a-hole kid kicked over my buddies bike and the brake light broke off. I can see where the 4 wires were soldered, but don’t know which went to what. Check the pictures below. I’m hoping someone has the same light, but intact. I also have measured the conductors when the brake lever is pulled and when it isn’t. Any input is appreciated. Thanks!

 

[E-HP]

What is the normal behavior? The left and right stay on as running lights, and the middle lights up upon braking, or all three stay on, and the middle gets brighter upon braking (or something else)?

 

[slaphappygamer]

On the PCB, I saw that only “N”, “GND”, “S-g”, and “S” were soldered to. I can tell by the blobs. The left and right (turn signals) never worked. They were not wired in. I saw the light once, when I put the bike together, this normally (outer 2 LEDs) is on (static) while riding and is brighter when the brake level is pulled. I think the middle light comes on when brake is active. I know it gets brighter.

 

[fill]

why not just test the pcb with a low powered battery or psu 6v should be enough to light up leds enough to see, gnd will be the ground or -ve connection so apply +6v to each other pad in turn and see what happens... if nothing try 12v . if still nothing try full bike battery voltage?? the big resistors appear to indicate it might have high power capacity but if im wrong applying too much voltage to start with could kill it.

 

[E-HP]

On the PCB, I saw that only “N”, “GND”, “S-g”, and “S” were soldered to. I can tell by the blobs. The left and right (turn signals) never worked. They were not wired in. I saw the light once, when I put the bike together, this normally (outer 2 LEDs) is on (static) while riding and is brighter when the brake level is pulled. I think the middle light comes on when brake is active. I know it gets brighter.

You can trace the ground terminals of the outer LEDs (flat side of the LED) to their common point for the black wire, GND. Do the same for the center LEDs, that point goes to the green wire, switched ground S-g. Interesting about the yellow and red. Is there any difference with the system powered up, vs off (switched)?

 

[slaphappygamer]

I was actually thinking of doing just that. Normally, there is full pack voltage. I figure I could use a 5v source, from usb power, as my test voltage. I'm not sure how would I be able to test the brake. The cutoffs are NO. Since the 5v is gone, when the brake is pulled, does that mean that the 5v gets grounded?

I thought that too, the red and yellow both carry full pack voltage. I measured twice to be sure. I'll have to check what the reading is when the bike is powered off. I only tested with the brake lever pulled and then released.

 

[E-HP]

If it's from the ebike brake circuit, then there is usually a pull up resistor that brings the signal line up to 5V, but the brake lever grounds that, cutting off the controller. I'm guessing the brake light leverages that circuit.

 

[slaphappygamer]

I'm guessing the brake light leverages that circuit.

Then the brake light will now have its ground to complete the circuit and it (led2) will illuminate? That sounds very possible. I'll have to test that scenario first. I have a very similar brake light on my bike and led 1 & 3 are always on, then led 2 comes on when the brake is active.

 

[E-HP]

Then the brake light will now have its ground to complete the circuit and it (led2) will illuminate?

Yup, that’s the idea.

 

[slaphappygamer]

I was able to gather more info on this. I tested and found that the bike display is off, the yellow has no voltage. When the display is turned on, the yellow gets 48v.

By using a 12v dc wall supply, I found that putting 12v to N and negative to GND, LED2 is active. When 12v on S and negative to S-g, LED 1&3 become active.

So I’m going to wire yellow to S, green to S-g, black to GND, and red to N. That should give me LED 2 always and LED 1&3 when the brake lever is pulled.

 

[E-HP]

I'm glad you're doing your due diligence and testing before wiring it up! Maybe your buddy will spring for some beers!

 

[slaphappygamer]

I'm glad you're doing your due diligence and testing before wiring it up! Maybe your buddy will spring for some beers!

Thanks! I quit drinking about 15 years ago. I’ll see if he has any ganja.

 

[slaphappygamer]

All wired up. Now waiting for the (broken) housing to dry since I had to glue the 4 pieces it shattered into back together. The bike is in a different location, so I’ll be able to connect it (the moment of truth) tomorrow.

 

[slaphappygamer]

Worked out great. A photo of the tail light and when the brake lever is pulled.

 

[E-HP]

Excellent!
Smoke ‘em if you got ‘em!

 

[fill]

Puff Puff,,

 

[slaphappygamer]

My buddy is giving me cash. So I’ll be off to my favorite local dispensary after work today. I appreciate all the input here.