Bike Cargo Trailer
By Gawain Tomlinson
San Diego, CA
Disclaimer: If you find this article useful, feel free to use it at your own risk. The author accepts no liability whatsoever for the information contained herein. No warranty is expressed or implied.
I found a pair of red LED trailer marker lights at the auto supply store for less than 5 bucks. They are perfect for tail lights.
I bought a pair of LED motorcycle driving lights for headlights on Amazon; they cost about $11.20.
2pcs Universal 4 LED Round Daytime Running Light DRL Car Fog Day Driving Lamp Waterproof White - Amazon.com
I made a fiberglass whip-mounted amber warning light for the rear of the trailer. The first version was pretty good, but I decided that it wasnít durable enough. It used a plastic prescription bottle for a lens. So I built Version-2 using a lens assembly from a commercial warning light, like they use on fork lifts.
I built an electronic controller which controls all of the lighting functions. I also built an 8 Amp/Hour battery box with a built in charger. 8 AH may seem like over-kill, but I figure I can power and charge laptops, tablets, cell phones, and whatever for a couple of people on camping trips. I plan to put brackets for a 15 watt solar panel on top of the trailer for camping. The electronics didnít cost much; a few parts from Radio Shack and Home Depot, plus parts I had lying around.
The light controller provides control for headlights and taillights, as well as the warning flasher. It fits inside a plastic quad receptacle sized junction box. It has a terminal block with +12V input and headlight, taillight, and warning flasher outputs. Two On-Off-On toggle switches provide control.
One switch turns on the headlights continuously in either On position. There is no electronic control of the headlights. +12V is simply switched to the headlights. The headlights are small DRL 4 LED running/fog spotlights from Amazon.com $11.20. The power draw is about 4W total, giving them about 24 hours runtime on an 8AH battery.
The other switch controls the taillights and warning flasher. The warning flasher operates in flash mode in either On position. The taillights are on solid, or on flashing, depending on the switch position.
The taillight switch is a DPDT switch. One set of contacts controls power to the LM556 timer, the other set of contacts controls the function of the taillights.
The flasher control is provided by an LM556 dual timer integrated circuit. The timer output drives two DC solid state relays (SSRs), which drive the LED taillights and warning flasher. Power transistors could have been used, but I used the SSRs because I had them lying around.
All of the parts except for the junction box and SSRs were purchased at Radio Shack.
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