Power/failsafe LED

Now I know the maths isnt hard, but I find this on-line resistor calculator very handy.

http://www.bit-tech.net/article/68/http://www.bit-tech.net/article/68/

All you need to do is type in the Supply Voltage, the Diode Forward Voltage, and the Diode Rated Current, and it gives your the value of the required resistor, including the power dissipation. It also gives the Next Standard 5% Resistor to make selection easier, and if youre not too hot on the resistor colour code, it tells you in words (e.g. Orange Orange Brown 330 ohms).

You do need to know the forward voltage and diode current for this to be of any real value, but these can be found in any Rapid or RS catalogues.

Made my life simpler anyway! :)

Thats useful for people, Bob. Note that 10mA is normally easily sufficient for an LED. You do not need to use the current in the datasheet that the forward voltage drop is specified at - less is enough normally.

Generally the datasheet will have a graph of voltage and current. For example, the LED here: http://homepages.which.net/~paul.hills/Temporary/Hewlett%20Packard%20HLMPK105.pdfhttp://homepages.which.net/~paul.hil...%20HLMPK105.pd f on page 3. The graph at the top left of page 4 shows the luminous intensity linear with current, but the human eye is sort of logarithmic, so halvingthe intensity doesnt make the LED appear half as bright.

Off topic this, but amazingly the retina cells in the human eye can actually detect just one photon!

Oh right. cool.

Mr Stu

is it not a good idea to mount a small peace of metal on to the removable link that could fit into fuse holder and then have the fuse holder next to the other half of the removable link on the robot then with a standard 9v battery power an led it would still go out when the link was removed and wouldnt go out just because there was a fault with the speedos in my mind it would be a lot simpler and possably more relyable would this be allowed

thats just trying to emulate the behaviour of a properly wired power led and acts as a get-around for the rules which is meant to be there for safety reasons and the led could go out if the 9v battery went flat and the robot could still be powered and a little punctuation in your posts wouldnt hurt nor would the odd capital letter :)

in all fairness jim i cant pic fault with anything youve said however i have no idea how to make the led come on without having it on a separate power supply because i have no idea where to put it on my speed controler if anyone knows where to place the power light on the 4qd ncc 70 i would be more than happy to do it but im not going to risk blowing up one of the most expensive peaces of kit in my robot for a rule that has more holes in it that a string vest and the reason i dont use puncuation as a mater of principal if we did without it before the 1500s we can do without it now :)

why do you have to connect it across the 4Qds? none of our power lights are connected across the speedos. We just use a 24v LED from RS, which can connect anywhere in the circuit.

Connect it between the main battery positive and negative leads after theyve passed through the link (with an appropriate resistor if necessary.) This is electrically equivalent to connecting it between the battery terminals on the speed controllers. Thats assuming you have a normal electrical setup.

I thought Id do a quick sketch to help you out with the wiring (see the picture on my profile) the Robot LED unit can be just a little panel-mount LED that you can get from Maplin, that will run at 24v (I used to make LED units, but I hadnt done the research and after Id started making mine I found maplin mass produce them which made them cheaper than the ones I sold :sad:) anyway, I hope that helps.

This is the final wording to be placed in the rules regarding failsafe lights. As agreed by the committee at last Saturdays meeting.

4.3
In addition to the main power light (See. Batteries and Power no. 6.8.) showing the main power is activated. An additional light may be fitted to indicate the robot is in a fail-safe mode. This will be at the discretion of the robot constructor. Even if such a light / indictor is fitted, the robot constructor will still be required to demonstrate that the robot is able to fail-safe under power. ref rule 4.2

Geoff Smith.
Chairman, Fighting Robot Association.

Hoorah!

The largest discussion on the forum finally has an end :)

We may not be quick... But we get there in the end! :)

But is the thread really dead, or has its power light just failed? :)

--
Fluppet

Andrew behave and shut up!!!! Let the thread die a natural death. We may mourn its passing but we may not prolong its agony.

Long live the next thread

wearing solomn black for the occassion.

Mike.

Ah so u do not actually need one then confirmed and understood.

we still havent decided on the color of the power yet, have we...

There is no preference to colour, so long as it is clearly visible.

can I have a neon strip under the robot like in the fast and the furious????? does that count as an LED cause it is a filamentless light....

lol
:)
Jamesbaker
troublemaker

No. Neons require a high voltage invertor which is in breach of the rules.

lol

You can now get LED strips that run on 12v like the Neon ones for under F&F cars just cost more but they look better, seen someone recently replace his Neons with LED strips. :proud:

Chris - http://www.featherweights.org/forum

what color led suits a black robot best ?

blacklight?

No its been resurrected!

The thread that needs an archive for its archive!

I would say white or blue

Green.

This could run and run lol!

IMHO blue looks best on most bots but is also the mose expensive.

Regards
Ian

Even though I shouldnt get involved here, I *will* say something (semi-)practical:
IMHO, itd be a bad idea to use a white LED. Itd be hard(er) to tell from a reflection of the arena lighting. Other colours Ill leave for other people to (re-)discuss. (Does alternating the colours on a multi-colour LED count as flashing? No, shut up Andrew...)

--
Fluppet

Sorry to start this again but I have 2 completly seperate circuits in my robot, 1is 24v and the other is 14.4v. I have two seperate links for these systems.

My question is, do I need an LED on both circuits or will just one do?

Regards
Ian

2

Yep.
Think about it Ian. If you pull the link or you lose power to the 14.4v drive side, you still have 24v power to your valve which is still armed and alive and ready to fire your pneumatic flipper. Even though the arena crew approach all robots as if they can potentially move/fire, it€™s miss leading that you have no LED on your weapon and it€™s armed. 2 LEDs like Ewan said.

Mr Stu

Yep 2 lights, Conundrum Mk1 has two lights one red and one green in the back because of the two systems and the link is joined together so it cuts both circuits off. Always passed safety checks.

Chris - http://www.featherweights.org/forum

Well you will probably all hate me for bringing back this thread but here we go,

If you were to use one of the fans to keep your robot cool as here http://www.overclockers.co.uk/acatalog/Online_Catalogue_Akasa_Fans_97.htmlhttp://www.overclockers.co.uk/acatal...a_Fans_97.html
and it was wired up to work exactly like the power LED which is required by the rules, would it count as the LED or would you have to have a seperate one?

This will make you lot unhappy from the sound of that IBC thread. In our pushy feather, Hellbringer, we had a 80mm computer fan with 3 rather bright LEDs in it. It was such a nice fan as it moved more air then my brothers desk fan. Anyway other then the lights on the IFI Victor 883s and the Volt Watch it was the only lights in the robot. It was also mounted on the inside surface of the robot with a 80mm dia hole to allow the air though and made it very visable.
Now for the bit you wont like. The fan was under the robot. With 10mm of ground clearance it caused a really nice red glow from under the robot. Everyone knew the robot was on. Do neons as we call them counts as power lights?

Why does the rules say Surface mounted rather then Clearly visable?

Im Australian and I dont think Ive every read any rules all in one sitting so you can ignore me if you want.

Let me hazard a guess here, quite a logical one...: in most of the arenas in Europe we have coloured lighting that changes constantly (spotlights) and that will drown out any glow that comes from underneath your robot. The issue is that we must be able to clearly see a distinctive lightsource on the robot.

Rule 6.8 - All Featherweights, Lightweights, Middleweights, Heavyweights and Super Heavy Weights, must have at least one surface mounted non-filament power light that is illuminated when power is supplied to the robot. (I.E. when the link is in.) The power light can be any colour but must be non-flashing and be in contrast with its surroundings.

I bought a blue coloured LED for my bot and then decided to read the rules afterwards (silly I know - shouldve read them first :)) The majority of my robot is blue and I thought to myself Well thats the LED useless since it doesnt contrast. But would it be suitable if the panel on which it will be mounted (which is clear to see, it isnt tucked away or anything) were to be painted completely white. This way the blue dot of the LED would be distinguishable. Would this be likely to pass a safety check seeing as it contrasts with the mounting panel or would the fact that the rest of the robot is blue count as its surroundings and not be allowed.

Regards,
Jamie

P.S. Theres a pic of it on my profile - imagine the panel with the Scotland flag was painted white with the blue LED in the middle

Why not put it in the middle of the St Andrews cross?

Lenny if its the type of blue LEDS alot of people use - im sure it will be more than fine.

Mr Stu

Cool, thanx for that.

Steve, I thought about putting it in the middle, but I wasnt sure about the contrast thing, but I might be tempted now :)

Sorry to resurrect such an old thread, but I didn't feel this question warranted its own thread....

I know the rule says surface mounted LED, but I've found my power LEDs are far more visible behind the HDPE armour, and also less prone to being damaged. Can I mount them behind white HDPE as long as they are visible, or will I fail the tech check on this?

Cheers,

Rhys

Obviously you mean with a hole for the light to shine through right?