wiring question for newbie

[Neil Powell 1Participant @neilpowell1]

Hi,

I'm trying to get my head around wiring for my twin motor bait boat. I've drawn a picture(be kind!) of how i think it should work using a switch with an LED. I also want to put an LED in the circuit to show when it is on and therefore remind me to turn it off(oh yes i will forget). Let me know your thoughts

Thanks Neil

[Neil Powell 1Participant @neilpowell1]

[ashley needhamParticipant @ashleyneedham69188]

Neil. Go to the home page and in the centre column is a v helpful model boat electrics article by guru Dave Milbourn.

Ashley

[harry smith 1Participant @harrysmith1]

HI Neil

This will work.

Harry

[Malcolm FraryParticipant @malcolmfrary95515]

With a "3 pronged switch with LED", Harry's green LED and resistor is usually inside the switch. Probably safest to ignore the third connection and use an external LED.

An LED takes, and will stand up to, a miniscule amount of current. As per your original drawing, it would be an instant fuse. It would blow way, way, before the main fuse shown.  Been there, got that Tee Shirt.

Edited By Malcolm Frary on 18/02/2020 10:07:23

[Dave MilbournParticipant @davemilbourn48782]

I would imagine the "3-pronged switch with LED" would have the centre contact as the common one, in line with all of the similar switches I've ever used. Many cheap illuminated switches use neons rather than LEDs, so I'd agree with Malcolm and fit a standard switch with an external LED. I calculate the ballast resistor value should be 430R for a standard green LED and 390R for an ultra-bright one. Do make sure the switch will carry the current you expect the motor to draw when it's loaded up.

Dave M

[Dave Cooper 6Participant @davecooper6]

Hi Neil

From my own experience, I would say that a simple on/off ('2-prong&#39 switch will suffice, unless, perhaps, you may want a third "test" position for certain accessories or something.

As Dave M says, make sure the switch is rated for maximum current draw (eg mine is rated at 6 amps for use with a 2 amp fuse). This gives the switch a good safety margin.

I would bench test your twin motors running flat out (for a very short period), just to see what they are drawing. Under load (ie in the water) it could be more…Also, check that your chosen ESC has an appropriate current rating.

Good luck,

Dave

[Neil Powell 1Participant @neilpowell1]

Posted by harry smith 1 on 18/02/2020 09:14:49:

HI Neil

This will work.

Harry

Thanks for the advice. This looks a bit simpler. What am i looking for when i buy the resistor. Is that 180 ohms?

[Neil Powell 1Participant @neilpowell1]

Sorry another newbie question. What does the resistor do? What voltage rating does the LED need to be?

[Neil Powell 1Participant @neilpowell1]

Ok so these are the LED's that i am planning on using. THey are flashing ones with built in resistor. Using Harrys example i'm guessing i don't need to use a resistor if one is already in the LED. Also will the circuit still work if the LED flashes on and off or will the motor be intermitant?

https://www.ebay.co.uk/itm/Ultra-Bright-Pre-Wired-Constant-Flashing-9v-12v-LEDs-Black-Prominent-Holders/141336194100?ssPageName=STRK%3AMEBIDX%3AIT&var=441886800571&_trksid=p2057872.m2749.l2649

Thanks again and sorry for all the questions

[Dave Cooper 6Participant @davecooper6]

Neil

The resistor in Harry's diagram is acting as a "current limiter". LEDs will blow (fail) at quite low current values so the resistor is there to 'protect' it.

Harry suggests 180 ohms, Dave M 390 or 430 ohms dependant on colour / type. Look up the spec' sheet for the LEDs you want to use.

If you want to experiment, (low wattage) resistors are dirt cheap. You can get a whole strip for less than £1. Start with a high value one and work down in increments until you get the brightness you want.

I've no experience of LEDs with 'built-in' resistors, but again the spec' sheet should give you all the gen' on that.

To get a particular resistor's colour code, just enter the ohms value into google and you'll get a pretty picture !

Dave

[Dave MilbournParticipant @davemilbourn48782]

Chapter and verse LEDs

DM

[Neil Powell 1Participant @neilpowell1]

Posted by Dave Milbourn on 18/02/2020 22:37:24:

Chapter and verse LEDs

DM

oh yes printed this out today. very useful and easy to understand. thanks

[Neil Powell 1Participant @neilpowell1]

So I'm guessing that the 12v LED's that I bought some time ago, that on closer inspection have a resistor under the shrink wrap, are just normal run of the mill LED's but with a resistor lowering the voltage!

Think I'm getting the hang of this now.

[Neil Powell 1Participant @neilpowell1]

Final question then I promise I will leave this alone. If I fit a resistor will the voltage delivered to the led's drop as the voltage in the battery drops.

I am planning on using an action electronics power distribution board so that I can use the as same battery for all the electronics. The battery will be a 3 cell lipo, I'm just concerned that as the voltage drops the LEDs won't get enough voltage

[Malcolm FraryParticipant @malcolmfrary95515]

Posted by Neil Powell 1 on 21/02/2020 12:07:13:

Final question then I promise I will leave this alone. If I fit a resistor will the voltage delivered to the led's drop as the voltage in the battery drops.

I am planning on using an action electronics power distribution board so that I can use the as same battery for all the electronics. The battery will be a 3 cell lipo, I'm just concerned that as the voltage drops the LEDs won't get enough voltage

As long as the battery voltage is higher than the LED vltage, the voltage across the LED will remain constant. However, as the supply voltage drops, the current through the resistor, and therefore the LED, also drops,resulting in less lght emitted from the diode.

[Neil Powell 1Participant @neilpowell1]

Posted by Malcolm Frary on 22/02/2020 18:59:26:

Posted by Neil Powell 1 on 21/02/2020 12:07:13:

Final question then I promise I will leave this alone. If I fit a resistor will the voltage delivered to the led's drop as the voltage in the battery drops.

I am planning on using an action electronics power distribution board so that I can use the as same battery for all the electronics. The battery will be a 3 cell lipo, I'm just concerned that as the voltage drops the LEDs won't get enough voltage

As long as the battery voltage is higher than the LED vltage, the voltage across the LED will remain constant. However, as the supply voltage drops, the current through the resistor, and therefore the LED, also drops,resulting in less lght emitted from the diode.

Thankyou Malcolm

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