design a scooter stop light

Firstly I want to say that I'm a newbie in electronics so please be patient.


I will try to explain what I want to do. I got a scooter for which I bought a top case similar to this one


There is this red plastic bit on the back of it which is not even reflective so I want to modify it to become more visible to other cars. What I was thinking of doing is to put some LEDs behind that red transparent plastic which will illuminate it. Basically I will drill many holes behind that plastic and stick LEDs into them. Now the tricky part is how to connect them. I want to connect them to the same power supply as the tail/stop lights. The scooter's lights are always on but when braking they illuminate more. I want the LEDs to do the same. I checked the connectors to the rear/stop light and there are 3 wires connecting to one Bayonet bulb similar to shown in this picture


Two wires connect to the bottom of the cap and one to the side. The bulb specification is 12V 21/5W. I assume one wire has lower voltage and produces less light (tail light) and the second wire more voltage and bulb becomes brighter (brake light). I was thinking of connecting some LEDs to one wire which will always make them switched on and the second wire to other LEDs and they will only switch on when the brake is applied.
Can someone please draw a diagram of how the LEDs should be connected together? Below is a diagram of how I was thinking of doing it. What specification LEDs do I need? Will they drain too much power from the main tail/brake light so it will not be bright enough. How many LEDs can I connect together so taht they don't cause any problems?

I wil appreciate all help, many thanks.

You got the jist of it- just need some fine tuning..
12V 21/5W- Both filaments are rated at 12V. One burns at 21 watts, the other 5.

Your wiring is missing an important part- the resistor. What I would do is to have all the LEDs on simultaneously, and use 2 resistors- 1 for tail light and 1 for stop light.

In the following example, we will assume the LEDs are rated at 2.0V @ 30mA. That means the string will use 10V @ 30mA, and we need resistors to 'dump' the 2 volts and limit the current to 30mA.

Brake Light- I would use a 100 ohm resistor, which will give you ~20mA
Tail Light- I would use a 220 ohm resistor, which will give you ~9mA
If both the taillights and brake lights are on, the current will be 29mA


You of course can use more than 5 LEDs. I would just copy it as needed- 10 LEDs/ 4 Resistors, 15/6 etc

Thank you for the reply.
I was thinking about using these SuperBright 10mm LEDs which have the following specs as shown on this site:
https://www.rapidelectronics.co.uk/rkmain.asp?PAGEID=80010&CTL_CAT_CODE=&STK_PROD_CODE=M35185&XPAGENO=2
Are these OK?
I will try to use 10 LEDs. If each LED is rated about 2V then will 12V supply be enough for 10 LEDs?
Can youy draw a diagram of how 10 will need to be connected.

Thanks

So to use 10 LEDs they will need to be 1.2V each? Do these exist?

One more question, if there are 2 positive wires (tail and break light) then each one probably gives 12V. In that case 2 separate strings of 5 LEDs can be used, one connected to tail light wire and the second to the break light wire. If I did do it this way I would need to use a 390 ohms resistor, right?

just to add my comment, if you want a wider viewing angle on the brighter leds, all u need to do is sand down the point on the leds, the less of a point the wider it gets ;-) hope that helps

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