Flashing LED tail light for e-bike

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1

Hi Core forum team,

I have made an e-bike using a mid drive 52v motor (TSDZ2) and 52v 17Ah LiPo battery.

I have connected a dc dc converter (20v/60v to 5v 10A) to the battery, and have connected a flashing LED headlight to this which works a treat and is nice and bright, which I like for safety reasons.

I have a few rechargeable tail lights, but since I have the 5v available from the dc dc converter, I would like to make use of that, and have a connected tail light, to avoid needing to recharge multiple devices.

I have looked for existing 5v lights, but they all seem to have rechargeable batteries with max charge of 1A, or are cheap lights powered by 2 AAA batteries. I thought, why not build my own (because that will be fun). Here is my plan…

  1. Purchase these or something similar…
    https://core-electronics.com.au/led-3w-aluminum-pcb-5-pack-cool-white.html
    or
    https://core-electronics.com.au/led-3w-aluminum-pcb-5-pack-red.html
  2. Build a circuit to flash the leds
  3. Insert the leds and circuit into an existing motorbike or trailer tail light housing or if using the red leds, possibly encase them in epoxy.
  4. Connect to the dc dc converter

Assistance I require…

  1. Advice on the best circuit design to perform the flashing of the specified leds, taking into consideration they draw 750mA, so the circuit will need to be able to withstand the current draw of the leds.
  2. Is a relay required?

Also please feel free to suggest alternate bright leds that might be a better option.

Cheers from Emma

2

Welcome to the forum,

This may not be as simple as you’re imagining. Not because it’s a difficult electronics problem but because there’s little you can buy off the shelf for 5V. If you can get 6V to 12V it would be much easier. The reason is, you need to current limit and also switch those LED’s on and off and everything I could find requires a minimum of 6V.

IF you electronics knowledge is good and your OK with designing circuits you can use a 555 oscillator driving a DIY buck converter. If that threw you read on.

The current limiting can be done with some big resistors but they’re going to get hot and you’re going to need a MOSFET to switch the power. Alternatively you could use an off the shelf buck type LED driver. Unfortunately the only off-the-shelf units I could find require a minimum of 6V and maximum of 36V. If you can get a higher voltage (6-36V) then you can use the below driver and switch it using the control inputs.

The flashing circuit can be done with a 555 time circuit or a microcontroller but if you don’t have the electronics and or programming knowledge that’s not going to be easy. There’s lot’s on the internet on how to make 555 timer circuits.

An alternative if you can get 12V is to use some motorbike LED indicators and a flasher unit. You may be able to find some 6V units that are likely to work at 5V. I couldn’t find any in a quick search. Most motorbikes now are 12V.

Good luck!

Note: I don’t work for Core-Electronics. I’m just another forum member.

Shaun

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3

Thanks so much for your reply and suggestions @Shaun21504

Your information has made me consider other options. I have found a 25/60v dc to 12v 10A dc converter, and have now more options for off the shelf 12v lights.

Cheers Em

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