Looking for insight on building an AFAD trailer

[crazybry79]

Ok, here's my project.

I work at a manure hauling company. We drive semis from the farm full of brown gold to the field. When we get to the field, we park on the side of the road and dump our contents into a roadside dumpster.

If we do this on a county road, seeing we block a lane of traffic, regulations dictate we must have "flaggers" (stop/slow sign operators). Only problem is finding labor willing to stand out in the elements.

I dug around, and according to the FHWSA, we can use AFADs (Automatic Flagger Assistance Device). More simply put, a trailer that sets where the Flagger would normally be. It must have certain operations (I'll describe in a second), and it may be remote controlled.

So here's my plan. I am currently building (2) AFAD trailers. At the rear most part of the trailer, there will be (2) 12" LED lights (red / yellow - picture a portable stop and go light, minus the green light). Immediately in front of the stop/slow light post, there will be a gate that drops down when the red stop light is activated. When the yellow light is illuminated, the gate will raise vertical, at the same time it will raise a shorter "slow" sign that will display.

On stop signal, the red light must flash for 5 seconds, then remain on steady. On slow signal, the yellow light must remain on steady.

On stop signal, an arm must be lowered (similar to a railroad crossing gate). The gate must have 3 lights along the gate arm. The furthest must remain on, the remaining 2 must flash alternating. (These 2 alternating flashing lights will also be wired to the tail lights, those will alternate flashing as well). The gate arm will be operated by a DC motor (think power window motor out of a car).

The AFAD will be powered by (3) 12v deep cycle batteries. They will be recharged via a small engine connected to an alternator.

The AFADs will be remote controlled, not automated (I will start another post on that issue)

I have drawn up a diagram that I believe will work. I'm looking for input on my diagram. Maybe someone can see a fault I made, or a better way to do something.

I appreciate the concern if anyone is wondering, but this plan / the AFADs are DOT/FHTSA approved.

Thanks in advance!

 

[Martaine2005]

Is this why they call you Crazy Bry?
That's a nice project.. Can you not find a secondhand unit that needs restoration of sorts?
Or possibly buy a main board and remote as spare parts from HERE.
Some nice information and specs HERE.
As much as I hate to say it, this is a job for a microcontroller.
Anybody else interested here is the info..

Martin

 

[crazybry79]

I think you've got the Crazy Bry thing figured out! ;-)

Those trailers in your first link are what we are attempting to replicate, just with a few more features. I'm a touch confused on those trailers, they state that the takers meet FHWSA guidelines. FHWSA states that AFADs may not display 2 slow signals at once, and the red must flash for 5 seconds before the gate drops. Either way I guess it's irrelevant.

I've looked for used AFADs, and when you can find them, they are cost prohibitive. My boss wanted to build a set of these, but didn't understand the electronics to make them work, so he lost interest. This is the point I decided to build these, and rent then to my boss.
The reason I used primitive / simplified electronics is I want the AFADs to be easily diagnosed when there is problems, and pasta to be readily available. BUT, if I knew a bit more about micro controlers, and if they're not cost prohibitive, I'll look into them.

And Google away I go!

 

[Martaine2005]

Hi Crazy Bry..
Good idea to rent it to the boss!!
Are those switch thingy's on the motor lines limit switches?
The drawings look ok. But it seems like everything will happen at once?
Getting the lights to flash for 5 seconds and then on constant seems to be a problem. That's why I mentioned a microcontroller. But I have no experience with them at all.
Somebody might be able to come up with some ideas. My only idea other than a micro would still involve a circuit and relays. But whether it would work is trial and error. That would be a 555 timer and a decade counter.
But I am sure somebody with auto wiring experience will have much better ideas.

Martin

 

[crazybry79]

Yes, the switches in line to the DC motor are limit switches. The DC motor operates the gate arm. When the gate arm in down, and the "go" signal is transmitted, power is applied to the relay (top one in the diagram). The relay will close (normally open), connecting power to the yellow LED. At the same time, the motor relay (center diagram) is given power and closes. This powers the motor that raises the arm. When the arm get to vertical, it opens the switch interrupting the power to the motor.

When the "stop" signal is transmitted, the receiver cuts power to the motor relay, as well as cuts power to the amber LED relay. It then supplies power to the red LED relay.

When the amber Led relay opens, it closes the 87a (I think) circuit. This circuit has a flasher in it (automotive style) that creates an on/off/on/off etc power to the red LED. At the same time, the red LED relay is energized. This turns on a 5 second delay relay (normally open timed close relay). This holds the circuit open for 5 seconds (the red led Is already flashing from the yellow relay's 87a). After 5 seconds, the timed red relay closes the circuit to the red led, giving it constant power.

The gate arm down is run off of the 87a of the motor circuit relay.