Instructables
Picture of Ready, Set, Go! Light
This is a project I'm currently working on for my local combat robotics club. It is an LED light system that will signal the drivers when the match will start. Here are the goals I was aiming for:

- Physically appear similar to an older style traffic light that suspends in the middle of the intersection.
- Be controlled without a microprocessor (i.e. no Arduino)
- Internal power supply that can run the system for several days.
- Be protected from shrapnel and flying robots.
- Incorporate sounds as well as lights.
- Be very bright and look cool!

Testing at home:



A video of it in action (with brightness toned down):



 
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Step 1: Circuit Design

Picture of Circuit Design
Like I said earlier I wanted to accomplish the timing control without the use of a microprocessor. I'm using the 555 timer IC as it is simple to use and also very inexpensive as well.

The circuit is designed to have a momentary switch trigger the first light, and the next light is triggered when the first light shuts off. Repeat as necessary.

The schematic I've hacked together here (props to kpsec.freeuk.com) shows how I've wired the red and yellow portions of the circuit. You have to add an additional 555 timer 'section' for each light.

I used 100k resistors to get an approximate time of 1.1 seconds for each cycle. If you replace R1/R2 with a 1 megaohm pot you can easily vary the timing of your circuit.

A typical 555 timer can sink up to 200mA of current which is more than enough for a handful of LEDs. In my case I am using 36 LEDs per 555 timer which draw approximately 120mA.

Step 2: Building the Circuit.

To solder my circuit I picked up a proto board from the local electronic supply store. Cost me about $5 and I could probably fit about 3 of these circuits onto it. I cut out the chunk that I needed with a dremel.

I tested the PCB with some single LEDs and it works quite well. The measured the circuit drawing about 30mA as it 'idles' with no lights on.
Robot Lover3 years ago
You could probably make a smaller circuit board if you use a 556 dual timer. :)
how much does this all come out to?
lks09124 years ago
VERY NICE STUFF...I AM WILLING TO TRY IT OUT..
tudgeanator5 years ago
 What actually happened to the one robot in the video? It just span around and then died, but why!?
travis7s (author)  tudgeanator5 years ago
It landed upside down and it wheels couldn't touch the ground. It looked like something broke off of it too so it might have lost power as well.
 
hemmikarl5 years ago
you could also use a the 4017 IC (decade counter) and a NOT logic gate to supply the power to the 555
(4017 pins
light1 = output0
light2 = output1
reset on 4017 = output2
not gate(in) = output2)
(NOT gate chip
the output of the not gate is to the power of the 555 and the input is connected to output2 on 4017(if using 2 lights))
to output up to 8 lights then you only need 3 IC's
RevZ5 years ago
I'm going to build a sprint starter light tree based on this idea. Any ideas how I can get it to work with four lights; 3 amber lights and a green "go" light? I need them to go on in 0.5 second intervals sequentially like this: 1 1+2 1+2+3 then stay on the green light #4 (or 1+2+3+4, doesn't matter) for at least a second or more. Any way how this can be accomplished? Thanks in advance for your help! Kevin.
frollard RevZ5 years ago
a 555 with a decade counter (each pulse from the 555 increments the light on the decade counter)

Have output 1 light up 1 led through a diode
have 2 output 1 and 2 led through another diode
/..etc
have output 4, 5, 6, 7, 8, 9 output to the 'green' led only, through a diode each.

http://bowdenshobbycircuits.info/page10.htm#traffic.gif
That follows the same idea, but uses a few transistors and runs a standard setup.
Sure, add some basic logic to a four-timer cascade. I've attached a simple block diagram, however Instructables handles images. (Never done this before - adventure!) Anyway, T1-T4 are travis7s' timer circuits, the diodes provide the logic for T1 to turn on only light 1, T2 lights 1 & 2, etc. T4 only turns on the GO light. (I left out power & ground connections.) Keep in mind you may want to add a driver stage for the LEDs - you'll lose about .8V in each logic diode (using basic signal diodes like 1n914 or even 1n4001s), so your LED's won't be as bright. It may work fine as-is, but keep that in mind if you have trouble. You should also be able to find info to calculate resistor/capacitor values for your .5 & 1 second delays without too much trouble, I think it's on the 555 data sheet, which you can find online fairly easily.
IMG_1090.JPG
travis7s (author)  TheOneTrueStickman5 years ago
That looks good to me. You could account for the diode voltage drop by adjusting the LEDs current limiting resistor no? I had the time calc formula on my schematic. using a 10uF cap and a 47k resistor gets you pretty darn close to .5 seconds. Find one close to double or just put two 47k is series for 1 second.
Ha, so busy with great ideas I didn't see the formula! And yes, the voltage drop could be helped by adjusting the LED resistor in this application. Hadn't thought that through completely. Other scenarios may present difficulties/oddities, though - Case 1: You end up with enough diodes to drop you below the forward voltage of the LED modules. Not likely with a 12V circuit, but could very well happen at 5V. Case 2: even with R adjustments, the way my logic is set up there could be either one or two diodes in there, which could make different lights run at slightly higher/lesser intensity. In this application I think that would look cool, but it might not be desirable. Also need to make sure the 555 has the power to drive all the LEDs/modules that need to be on at once. That's probably the bigger problem/reason to use a driver transistor, actually. Depends on the LED current draw.
Sorry the image is a pain to read, I wasn't sure how it would show up. Click for a bigger version.
travis7s (author)  RevZ5 years ago
Hmm.. I'm not sure if there is a way to keep mulitple lights on. I'm really busy right now but after this weekend I'll see if I can figure something out.
frikkie5 years ago
I like your idea.I know there is a circuit also doing the traffic light effect but which uses three transistors.
maestro85 years ago
The 555 is not a perfect source. Check out Thevenin's theorem for details; the actual source has a non-zero output impedance. In the simplest case, it acts as if it has a built-in resistance. Your selected current limiting resistor allows for plenty of source fluctuation. Good design there. In this case you don't have to worry about the output stage, but keep it in mind for future projects. If you really want to crank up the flash, consider adding an overdrive circuit (another 555 and transistor). Check out the data sheet for your LEDs, but you can pump a lot of juice into an LED for a very short amount of time without doing any damage...
maestro85 years ago
Just because the 555 can source 200 mA doesn't mean you should draw that much. The 555 wasn't designed as a stable current source, and LEDs need a stable source if you want to drive them safely and efficiently. How are you to choose a current-limiting resistor if you don't know the source voltage? Consider the case when one of the LEDs in your array dies. As the current put out by the 555 decreases, the output voltage will increase, sending more current to the other LEDs. This may lead to a cascade failure if you're driving the array near its limit. You don't need much more than a transistor and a couple resistors to make a suitable current source... why not put it in your design?
travis7s (author)  maestro85 years ago
I'm not sure I understand. I was under the impression the 555 outputs its input voltage, which is a fixed 11V battery. The current limiting resistors were selected for a source voltage of 15V (car alternator). Rest assured driving transistors was already supposed to be in the design, I just didn't have time for this version of the lights.
Gonazar5 years ago
Why is the second row of LEDs offset? Is there some sort of benefit to doing that?
travis7s (author)  Gonazar5 years ago
The main reason is there had to be that mounting hole in that spot for the original project. No real benefit.
Yeah, i noticed that too...?
AccountZ5 years ago
Definitely very bright, and very cool. I think it looks great.
lemonie5 years ago
It's good - what sort of match is this for starting? L
Kiteman lemonie5 years ago
Something messy, I'm guessing, since it need protection from shrapnel and flying robots.
lemonie Kiteman5 years ago
I would hope so. I've thought that blowing graphite-flake at your opponents might be a great weapon: dry-lubricant & electrical conductor? L
Kiteman lemonie5 years ago
In most combat robot contests, it is against the rules to use projectiles that detach from the robot. Unfortunately.
lemonie Kiteman5 years ago
Fire was used, that's borderline? (or was that just Sgt Bash?, long time ago...) L
Zilduli lemonie5 years ago
Is fire really a projectile? And if so, it doesn't really "detach" from the robot. It seems to me that the proper term would be "released".
lemonie Zilduli5 years ago
If the flame is not connected to the machine the burning fuel is detached. Projecting butane isn't much different to blowing graphite in terms of "spray". I wouldn't consider either to be projectiles. L
travis7s (author)  lemonie5 years ago
I double checked the rules at botleague.com, I think this would fall under "12.2.3. Powders, sand, ball bearings and other dry chaff weapons are not allowed"
Ah, thanks for that information. L
travis7s (author)  lemonie5 years ago
Flames are allowed at the discretion of the guy running the show. The graphite would probably not be allowed.
Kiteman lemonie5 years ago
The BBC version allowed the house robots to break the rules, including flammables.
travis7s (author)  lemonie5 years ago
If you ever saw 'Battlebots' or 'Robot Wars' on TV its the exact same thing, only on a smaller scale.
Yes I used to watch Robot Wars, there were some truly great machines, amongst the cac that got mashed... L