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Author Topic: Leds on MTB Exhausts  (Read 1222 times)

Captain Flack

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Leds on MTB Exhausts
« on: June 12, 2017, 02:40:55 PM »

Many, many years ago I read an article about a modeller who had installed red lights (it might have even been before leds were popular) into the exhausts of his MTB which glowed linearaly? %) when power was applied.  Try as I might I cannot find the article, despite putting it somewhere really safe for future use, and now am at the stage where I would like to do the same thing for my MTB.
Does anyone have any idea how this might be achieved?
Any help would be much appreciated.
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Martin [Admin]

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Re: Leds on MTB Exhausts
« Reply #1 on: June 12, 2017, 04:04:36 PM »


If you are using DC motors, you could link connect LEDs direct to the motors, probably though the judicious use of a resistor Voltage divider circuit......  Malcolm Frary will know all about this stuff!

https://en.wikipedia.org/wiki/Voltage_divider

( Different kettle-of-fish for not using Brushless motors! )
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malcolmfrary

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Re: Leds on MTB Exhausts
« Reply #2 on: June 12, 2017, 04:48:31 PM »

Following the usual rules about restricting the current through the LEDs, there is no reason why they should not work when connected across the motor terminals.  However, if it is a reversing motor, and if they are to work more than once, each LED in the chain will need another connected in parallel, but reversed, to protect its mate when reverse voltage is applied.
Use blue ones if warp speed is anticipated.
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dazzle

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Re: Leds on MTB Exhausts
« Reply #3 on: June 15, 2017, 08:08:56 AM »

This for leds,

Easiest is a small bridge rectifier smallest rated is about 1 to 2 amps rating is not important as leds only draw milliamps (ma), 20 ma  is the maximum i use even though most have a maximum rating of 30 ma above 20 ma will shorten their life, the high brightness ones are normally bright enough at 10 to 15 ma, i always use a separate resistor on each led to limit the current as even if from the same batch the brightness of each may be different,
 i e only example values, you may need a 330 ohm resistor on one and a 390 ohm on the other to get the same even brightness.
The  bridge rectifier will come with the ac side and the + positive and - negative output marked,
Two wires soldered to the ac side go to the motor though marked ac a bridge rectifier will accept a dc input on the ac side as well, the motor can be reversed the input polarity will change swop sides but the output + and - will remain constant and will not change, the leds  connect the same + to + and - to -
The bridge rectifier will put no load on the motor what so ever.

You could use 4 silicon diodes in a bridge configuration but what confuses most peeps, the ring marking on a diode denotes the cathode - negative end it is the two - cathodes soldered together is the positive + output, early metal ones were marked with + and - signs, idiot who brought out the ring system of marking what a doughnut.


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dazzle

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Re: Leds on MTB Exhausts
« Reply #4 on: June 15, 2017, 09:46:44 AM »

More fun if i had added the rest,

The two anodes + are soldered together and are the negative - output

One has then 4 ends left the positive anode is soldered to the negative cathode the same is done to the other
side the positive anode soldered to the negative cathode these two junctions are the input and can be from an ac source
or a dc one that can be a negative or positive input on either side hence the motor can reverse so the input will swap from a negative to positive one side and positive to negative the other side, the output thank gawd will remain the same.
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boneash

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dazzle

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Re: Leds on MTB Exhausts
« Reply #6 on: June 15, 2017, 08:17:19 PM »

Yep there the little beasties i use, normally i get a pack of 10 from the bay, ta boneash save me trolling through my purchase history on the bay to look up the wo8m 1.5a number also knew that would be the easiest for Captain Flack,
other handy thing about them, with two bits of heat shrink on them to insulate from the other two legs, you can push  the legs of the bridges ac input straight into the small red two wire battery connector plugs, plug wires go to his leds,  red matching battery socket its two wires go to a small  screw terminal connector that go's to his motor.
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Captain Flack

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Re: Leds on MTB Exhausts
« Reply #7 on: June 16, 2017, 12:03:14 PM »

I knew you chaps wouldn't let me down.  Thanks very much for your input, much appreciated.
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