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LED Bulbs pt2

Further help please

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Gary Murphy 120/02/2019 14:11:02
411 forum posts
14 photos

Hi Guys, Sorry to post again. I really know nothing about electronics and can not find the info I need. its not laziness. The sound side and power connection I have found on youtube vids.

I now know about the LED and resistors BUT when I looked at connection at the unit,its beyond me and the manual which I have linked below does not help me.

I will post a picture of the unit ,the 10 strand multi ribbon on the right is where you connect leds. The only tip I can find regarding light connection is, split the ribbon into 2 ,5 wires each and use 1 per vehicle side for neat wiring!

I have no idea if 1 led is per strand? is the black wire neg for all led`s?

If anyone can make heads or tails out of it,that would be great. And keep simple for a dimwit



Frank Skilbeck20/02/2019 14:23:46
4674 forum posts
101 photos

Gary looking at the circuit schematics, this is 10 "outputs/returns" from each LED (you need to include the correct resistor to go with the LED) and these are all the -ve connection, the +ve supply is common from connection no8 on the opposite side of the unit. The +ve supply voltage is the same as the supply battery so you will need to select the resistor to go in series with each LED appropriately.

Plummet20/02/2019 17:51:23
1418 forum posts
41 photos


As Frank has said, the connection should go from "8" on connector X1 [LHS] to one of the pins 1-8 of X3 [Lower LHS] as shown in the manual on page 46.

The X1 pin 8 is the +ve supply. The X3 pins are switched so that when switched on current can flow from +ve supply, through your leds, and to 0V (the other side of the battery.

You ask about leds in strands.

I am not sure what you are asking.

A. You might have some ready mounted strips of LEDs in some form of ribbon.

B. Or you may be wishing to put several leds in series, linking the +ve of one led to the -ve of the next.

C. Lastly you might be wishing to put a number of LEDs in parallel, that is, all their +ve s connected together, and all their -ve s connected together.

An answer about the resistor requires that we know which of the three you are trying, and also what supply voltage you are using.


Gary Murphy 120/02/2019 18:26:49
411 forum posts
14 photos

Thanks guys ,I will have to sit and read that several times for it to make sense to me. That is way more than I got from the manual gargon.

Plumet, regards the strands. I see 10 wires in that ribbon connector so wondered if 10 leds was all it could take? Split 5 per side.

Being a RC truck, it needs running light,dipped and main. I think 1 bulb can be used for all three,varying brightness by voltage.

Winkers/hazards , 6 bulbs so far.

reversing lights , 8 so far

fog , 10 far

This is just rough estimate till I sit and see if some can double up for use

Can I get more bulbs by using series or parallel ?

Once again thanks for taking time to help

Denis Watkins20/02/2019 19:06:31
4325 forum posts
104 photos


The Schematic Diagram tells the whole story

And if you look through, this modular approach makes the job simpler

There are 12 LED outputs


Fogs can be parallel

Reversing Lights parallel

The 6 winkers, 3 each side need switching for L and R but then a new bit of programme to

Switch all 6 Hazard lights On and Off simultaneously

Headlights need full power, then switched less for dip

All that is less than 12 outputs, so you have plenty

Your programme would then Sound the motor etc etc

Plummet22/02/2019 12:49:14
1418 forum posts
41 photos

OK, so I understand that the "strand" is the 10 way cable that is attached to X3.

This means that you can control up to 10 LEDs or groups of LEDs.

Consider this (rather scruffy) circuit diagram.


Here we are controlling two groups of LEDs. The two switchy things at the bottom left hand corner are playing the parts of two channels of your controller thingy.

The leds in group A are in series. Those in B are in parallel. The two boxes at the bottom are two resistors.

Now suppose that your battery produces 12 volts, and that each LED drops 2 volts when shining and needs a current of 15 mA (0.015 Amps)

If you want to think of electronics as being a bit like plumbing, then the Voltage is like water pressure, and the current is the amount of water flowing. We might say that the watery battery generates a pressure of 12psi. and that each LED will have a pressure drop of 2 psi across it. The resistors are there to limit the current in each branch. If they were not there then too much current would flow and the diodes would expire.

Looking at branch A. The same water/current passes through each LED. So the total current in the branch, and flowing through the resistor is 15 mA. However each LED is dropping the voltage/pressure by 2, so the 4 LEDS drop a total of 8 Volts/psi. Thus the resistor must drop 12 - 8 = 4 Volts/psi.

Compare branch B. (First we must assume that all the LEDs are identical. This assumption is not always possible to satisfy, so using LEDs in parallel is often a bad idea.

There will be 15 mA flowing through each LED, so a total current of 60 mA must flow through the branch B resistor.

The volt drop across the LEDs will be 2 volts. This means that the resistor must drop 12 - 2 = 10 volts.

By Ohms law ...

V = I R


R = V / I

Resistor A must be 4 / 0.015 = 266 ohms,

and resistor B is 10 / 0.060 = 166 ohms.


Gary Murphy 124/02/2019 17:53:16
411 forum posts
14 photos

Dennis,Plummet, Thanks for the detailed explanation. I wish I could say "i get it now" because I do not BUT I understand more than I did.

I am one of them people who can not read stuff and make sense of it. The Module makers have several vids on power connection,watching them I knew what to do BUT reading the manual prior I was lost! Just not very bright I suppose.

I am determined to use this module RATHER than a more basic plug and play Tamiya unit.

Dad_flyer24/02/2019 20:46:40
278 forum posts
306 photos

Diagram A from Plummet will work well. LED brightness is set by the current, and in that setup all the LEDs get the same current, going through one then the next. It would even be ok for different colour LEDs if they are designed for the same current. You need a high enough supply voltage for the sum of the LED voltage s.

Diagram B shares the current between several LEDs. If the LEDs were identical, then the shares would be equal, however the characteristics of LEDs make that unlikely even for LEDs from the same bag. They will take different current and be different brightnesses. The brightest may even blow. To put the LEDs side by side, each column needs it's own resistor to set the current. You can combine them together after the resistors and before the switch.

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