Power/failsafe LED

[_jl_]

Power/failsafe LED

Depends on how the speedos look (electrically, that is). If it is 100% capacitive (which I don´t think it is) the LED would go out.

[_jl_]

Power/failsafe LED

So....is this silence to be interpreted as good idea or too stupid to be commented?

[teamchip]

Power/failsafe LED

Probably neither Jonas...more likely folk are just bored with how long this thread about a simple LED has gone on, everything has just about been argued to death.

Tom

[jim]

Power/failsafe LED

It may be simple to implement in your situation, but bear in mind that there are an infinite number of robots that are valid within the current rules. Saying this is simple without any qualifying comment gets us nowhere.

[_jl_]

Power/failsafe LED

Thanks for reading before you post...:P

[grant_ploughbot]

Power/failsafe LED

Oh btw, many people have been putting the LEDs directly onto the Battery eliminator curcuit, do not do this as it draws too much currunt from it and the receiver just shuts down.
Although if you have a seperate battery pack for the receiver, this may be a good simple idea

Grant-PloughBot-Team Rc Wars

[jim]

Power/failsafe LED

Really? What kind of LEDs are you using? and what kind of BEC? They shouldnt be drawing a large amount of current.

I run mine directly off the main battery, after the link.

[grant_ploughbot]

Power/failsafe LED

I use 12v standard LEDs, and i do run it straight after the link.
But i have known a few teams such as Rampage who have tried putting them straight to the BEC.
The BEC only gives out a very small current anyway, but even a standard LED will draw too much of it from the receiver.
Just incase people try to fit their LEDs on the day of an event, make sure you dont make that mistake or you might not realise why your robot wont respond!

Grant-PloughBot- Team Rc Wars

[jim]

Power/failsafe LED

Which type are you refering to when you say the BEC? Some are capable of delivering a couple of amps or more, and would have no trouble runnning a dozen LEDs with plenty left over for the reciever. Across the main battery is the way to go, though.

[fwsorg]

Power/failsafe LED

BECs should be easily able to handle the current an LED draws- but quite some considerable margin- remember theyre designed to run Servos. Im not entirely convinced that that is the cause of the problem.

[grant_ploughbot]

Power/failsafe LED

Erm, well i only know about this from electrolise, and its the same with a few people, so they must just have very low currents.

[talulah]

Power/failsafe LED

Grant, what do you mean by 12v standard LEDs? An LED will only drop around 2v when supplied with 10mA - which will be plenty bright enough.

Therefore for 10mA, if you are connecting an LED across a 12v battery, it should have a series resistor of (12 - 2)/10mA = 1kOhm.

If it is connected on the output of a +5v BEC, all of which can easily supply 10mA, then a series resistor of (5 - 2)/10mA = 300 Ohms should be used.

If you are talking about directly connecting a normal LED across the BEC, then it is quite likely that it will pull down the BEC output voltage - up until it burns out of course - since a typical LED will be pulling over 1 Amp with 5v across it.

[jim]

Power/failsafe LED

You can get 12V LEDs which are just LEDs with an appropriate series resistor built in for operation at 12V. Its a possibility though - what value of series resistor were Rampage using with the electrolize BEC?

[grant_ploughbot]

Power/failsafe LED

im not sure about rampage, as far as i know i think they put it directly across the BEC.
Im not too sure actually what resistor i use, its linked upto 24vwith a resister which i thought limited the LED to 12v. If not i must have this all wrong, oops. But i know i deffinatly connect them to 24v, but my dad bought the resistor and LED, so i must have got mistaken somewhere.

Thanks
Grant-PloughBot-Team Rc Wars

[jim]

Power/failsafe LED

I use high brightness LEDs which can handle 30mA and have a voltage drop of 1.2V. I use them at 24V, and (24-1.2)/0.03 = 760 ohms, so I use the next value resistor up, 820 ohms.

Connecting an LED directly across the power supply even at 5V will normally destroy it in seconds. At 5V, I would reckon on a 200 ohm resistor for a normal LED.

Note that at 24V the resistor is dissipating quite a lot of heat - (0.03*0.03*760) = 0.7W. Make sure you get a resistor rated for this amount. Most cheap types are either 0.25W or 0.6W.