Another Take On The Rear-window LED Marquee


This rear-window LED marquee will help let the driver behind you know when you’re planing to change lanes or make a turn. But it also includes the ability to send a message like “Back Off!”. [Robert Dunn] was inspired to undertake the project after seeing the one we featured back in October. We’d say his has a better chance of being street legal since it uses all red LEDs.

The marquee is a matrix of 480 LEDs, all hand soldered to form the nearly transparent 48×10 grid shown above. This is important to preserve visibility out the back window of his truck. It makes us wonder about the feasibility of using SMD instead of through hole components. That would certainly make it even less visible when not illuminated, but the assembly process would be much more difficult. That’s because the 5mm LED packages fit nicely in the grid of holes he drilled in some plywood which served as the jig during soldering. The presence of leads also made the soldering process manageable.

Power to an Arduino board is provided from the cigarette lighter adapter. A set of six shift registers drive the columns while the rows are controlled by a 4017 decade counter and some transistors. Check out the blinker test video after the break to get a look at what this can do while on the road.

40 thoughts on “Another Take On The Rear-window LED Marquee

    1. Yes. Ginormous LED billboards are allowed to blind, flash, and distract. But put something blinking on your car and you are toast. Be sure to check your local vehicle code so you know your options.

      1. If you use amber LEDs, then you are allowed to use that in every state in the US at least. They are just considered the same as ‘caution lights’ as plows or utility worker trucks would use. No special purpose or licensing required for them. Blinking red LEDs are allowed for standard purposes like turn signals, and you aren’t allowed blue or white lights in most places.

        Given that these are so much less bright than even brake lights, I wouldn’t see anyone taking issue with this.

      1. You simply pass them at the next opportunity & let them catch up to you. I often pass someone who has just passed me to avoid kicking off the cruise, because they who where in a hurry wouldn’t move it on out. not that action irks me enough to put a message board on the rear of my vehicles, bat a dim ’em dammit light couldn’t be a bad idea.

        1. I installed a piece of plexi coated with a mirrored tint. I can see out, but if you are brighting me or are a moron in a pickup truck tailgaiting, It’s aimed so that the headlights of the truck will reflect into the eyes of the driver. Back off to a normal distance, and they dont blind him. it works great. Idiots that own SUV’s and pickup trucks dont ride my ass very long as they get blinded badly. One chick was so stupid she tried brighting me while tailgaiting. she backed WAY off after she did that and waited the 6.2 seconds for me to pass the semi truck and get over.

          1. Does not sound so difficult to make. Just have to measure how tall those sport utility vehicles headlamps are off the ground then what angle to make the mirror tinted plexi so the light is reflected back when too close. Just a few measurements and you are set. Plus having a friend to help with the project will make it easier.

    2. Most of the local forces I’ve checked with in Michigan argue that it’s only legal as long as it’s not “animated”; if you can and do change the pattern programatically to different pattern sequences they consider it animated. Doesn’t matter if it’s all red.

  1. whats wrong with using the horn to alert somebody of your prescence if you feel you have been wronged?
    I guess its because americans just beep the horn all the time for no reason being stuck in traffic and it has lost all meaning.
    Anyway antagonising someone on the road is a pretty stupid thing to do.

      1. really depends on what state for example here in florida is very quiet but when i went to new york it was a disaster ( at least the last time i went), people were in the middle of the intercetion beeping their horn non stop while the light was red and everybody was trying to go at the same time as if the street light wasn’t there.

    1. I have heard of people here in Alabama being ticketed for “unnecessary sounding of horn.” I kid you not. When I see people do something really stupid or throw lit cigarettes or trash (yes, people do this), out the the window, I lay down on the horn. Alabama is a beautiful state, but unfortunately many of its citizens do not appreciate this beauty.

      1. i once saw my brother get out of the car at a light and pick up a lit cigarette butt someone had tossed out their car window and pick it up and flick it back into their car while telling them “you dropped this”.

  2. At least once a month I seriously consider building one of these onto the grill in FRONT of my truck with messages (typically for PRIUS drivers) like “AT LEAST drive the speed limit” and “Does it really take 5 blocks to reach 35 MPH???”

    Either that, or a bumper stick printed in reverse for the front bumper that says “If you can read this, you’re not driving fast enough” :-)

      1. You can get in trouble for driving hazardously or interfering with the flow of traffic for driving too slowly, just as easily as you can get a speeding ticket for going too fast.

        They’re probably more likely to let it slide if you have a reason to drive slow(weather, fatigue, age, etc) but there is never a legit reason to go too fast.

        1. Check your state traffic code for sections on driving too slow, impeding the flow of traffic etc. If your state has such, write the police and kindly ask them to ticket all the a-holes driving 45 MPH on 65 MPH two lane roads.

          1. typically driving more than 15 mph below the speed limit in safe conditions is cause for a traffic citation. of course, driving more than 2 mph below the speed limit is cause for me to lean on the horn for a minimum of 30 seconds longer than it takes for the offending driver to get the hell out of my way.

  3. The blinker test is confusing.

    It simultaneously tells a following driver (1) I am about to change to an adjacent lane–as indicated by the turn signal, and (2) you should move to the adjacent lane–as indicated by the animated arrows.

    1. NateO is exactly right. Animated arrows are always to direct approaching drivers to go around in the direction of the arrow. This is very common on slow moving or stopped utility and road crew trucks of all kinds, tow trucks, plows, etc. You are going to cause an accident when someone tries to go around you because you do not understand what you are signaling.

  4. Nice hack, but in most EU countries it is illegal to modify external lighting of the car, when it is moving on public road. The list is different from country to country, but typically includes any modification to head- or taillights, turn signals, any additional license plate lighting decoration, undercarriage illuminations (yes, I’m talking to you ricers :-P), and any active (shining) displays on any window.

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