Thank you for that information Graham.

Martin555.

Ready made resistance boxes are readily available on-line like this one.

Even cheaper from China, but goodness knows when they would be delivered.

Graham93

Thank you for the information Ianh.

Martin555.

Component Shop has all the Calcs Pretty Easy

Guten Appetit Marky 😋😁
😎

Sorry Fleet ,eating humble pie (could be apple)as I type my grovelling apology,"your workbench really is untidy" and is setting the right example to us all.🤣🤣🤣.
Cheers Marky 👍

Cheeky b****r!!😁
You DO want to make Captain don't you Commander?😉
FLEET//
😎

See you've tidied up the bench for the "photo shoot" Doug 😏.
Cheers Marky👍

Thank's Doug,
Much appreciated.

Martin555.

Hi All,
Just a coupla pics of a typical 'mess' on my 'electrickery' bench (that's electricackle for JB😁)
showing some breadboarding tests with LEDs.
From the left:-
- a simple flasher (😮🙈) for Ed's Brooklyn,
- the basic 'lash up' enabling me to test LED/resistor combinations in series and/or parallel at various voltages from my variable PSU and check the current draw and brightness,
- a lash up to test SMD LEDs for a mast arrangement,
- testing 5mm LEDs for Haig (Down Under) for an 'all round' strobe flasher. His will be All blue!

The 'chocolate block' octopus at the bottom is a work in progress, the result of me wanting to test the newly arrived Action RC switches, and getting peed off with the plethora of different connectors, or none, on stuff we buy🤔 So, instead of making up yet another pair of leads for the PSU I decided to make an adaptor/distributor for all the different connector types, plus open wires.😁 Provision is made for connecting an ammeter and/or external lab multi-meter.
I can also connect the little Wattmeter to it if I want to run motor tests, using LiPos on the input for more than the 5A the PSU provides.
A fuse board can also be connected in series with the input. Has a socket for car type fuses or a 30A circuit breaker. For brushed motor tests a two colour LED (red/green) indicates forward or reverse.
The little Robbe Servo Tester box on the far right can be added to test run Servos, switches and ESCs without having to fiddle about with the TX and RX.

Sometimes I think I spend more time making jigs and gadgets than model making.
But it will save time in the long run. Honest Injun😁
"Sometimes it is difficult to concentrate on your original objective of draining the swamp,
when you're up to your arse in alligators!"😮
Now then - back to the pink gin😋
Cheers, All. Keep healthy and sleep well👍
Doug 😎
PS The construction bench never seems to look much better🤔

PS
Just added a few breadboarding bits and pieces to your 'Corona Relief Package' list Martin.
Gotta huge bag o bits on special offer some time ago😊
Keep on modelling folks (NO! Not gents underwear🙄 U disgusting bunch😁)
Ouch! Other wrist slapped now😭
G'night all, 😎
(Stage direction: slopes off to man-cave (stage right) chuckling hysterically!)

Never does any harm to do a bit of brain storming Martin👍
" have not got a glue"
Sorry if things got a bit 'sticky' Martin 😁
Aw shucks! Slapped wrist from the Sea Lord again🤔
😎

Martin,

Not a waste of time for me. Gave me something new to think about. I might even have a go at making one if I can find some suitable bits in the spares box.

As Doug says, a plug in breadboard is really useful for trying things out like this before soldering it together. Makes it really quick to swap components.

Graham93

Thank's again Doug and Graham.
It has proven to me that i definitely have not got a clue when it comes to electronics.
Sorry if i has wasted everyones time today.
I will now disappear back under my rock.LOL!

Martin555.

Hi Graham,
I agree with every word you wrote👍
BUT; I first sketch the circuit(s), calculate the resistors, pencil and paper and calculator suffices. THEN I suck it and see.
I mock it up on a 'breadboarding' jig, chunk of Vero board and some PCB pin sockets strips, to test. See attached pics. These were for 3 or 5mm LEDs for tug setups, was easy to 'plug in' the LEDs and resistors and adjust as required.
I've also done similar for SMD LEDs but with the SMDs soldered onto Vero board.
I suggested 1/8th W resistors before Martin mentioned parallel circuits!
That changes things, 1/8th W is then not enough. See examples below.

I too have reservations about the multi-turn pots. Apart from low current capability.
I've used them for adjustments / trimming in timing, pulse decoding ccts and often find them too insensitive for accurate measurements. Need about a 50 to 100 turn pot, rare as rocking horse droppings and expensive🤔 But at least better than a mini carbon track trim potti.
Appreciate your efforts but I really don't think such a rig is worth the effort.
Each to his own👍 Up to Martin now.
Cheers, Doug 😎

Hi Graham,
Thank you for your help and advice.
After having a good look around through the odds and ends i have it looks like i will have to put this idea on hold for a while.
Tomorrow i will venture out in to the shed and have a look around.
I will go armed as those spiders are massive and attack in gangs.

Martin555.

Hi Martin,

The circuits you posted are fine. You would only need two banks of resistors - 10 ohm and 100 ohm. My drawing is basically the same thing but based on a couple of rotary switches rather than DIP switches. Something like this:
https://www.ebay.co.uk/itm/1-2-3-4-Poles-Rotary-Switch-Solder-Terminals-150mA-250V-Lorlin/254303918379?hash=item3b35b1d92b:m:mEgTeKtkfy0fqz-sR5t99GQ

Either of these circuits will work fine on 6v up to 12v+. The resistance range of 10 ohm to 1000 ohms should cover any requirement within this voltage range. As Doug says 1/8w resistors will be fine. Higher power 1/4 w even better.

As Doug says, it is easy to calculate the value of resistor needed for a defined current, but I find it is better to try it an see as the current doesn't tell you how bright a led may appear.

A multiturn pot is another option, but they tend to be expensive and most of them are not designed to carry much current. If you need 20mA to get the brightness you need with a LED, and hence you are using a low value of resistance, there is a lot of power being dissipated over a very short length of the carbon track in a pot.

Graham93

I reckon so Martin🤔
Woz only pulling your 'anchor chain'😉
😎

I just want to say to all of you guys a big thank you for all the help and advice.

Martin555.

Doug,
Ref: Flower class. OK. Maybe you could finish it off sometime like your U-Boat; transparent hull so we can see what's happening inside!?

I think that will be a lifetime of work and i don't think that even i have that amount of patience.

Martin555.

OK, will do👍
"It is looking more like i should continue with the way i have been bumbling around up until now."
That's fine for testing a few LEDs, just to make sure they work at all.
I use the little box in the pic for that. Works on a 9V block.
Only a few quid off the 'World Wide Market'.
Cheaper than I could buy components for, and not worth wasting time to build one😉
Use the calculator for complex LED circuits.👍
If you use the Guru it will give you combi series/parallel circuits, to reduce the total current or voltage needed for the same number of LEDs!

Ref: Flower class. OK. Maybe you could finish it off sometime like your U-Boat; transparent hull so we can see what's happening inside!? 😁
Cheers, Doug😎
Sorry to have squished your Deca Box idea😔 But it's not really worth the time and effort!

I have a Matchbox 1/72 scale Flower class kit that someone had started somewhere up in the loft.

Martin555.

Excellent Doug,
Yes please if you could i will be most grateful.
REF:- Deca box
It is looking more like i should continue with the way i have been bumbling around up until now.
Thank's again.

Martin555.

BTW #99 Martin😉
Have you already built a Revell 1/72 Flower Class Corvette, or have a kit for it?
Cheers, Doug 😎

"Should i fit a resister at the lowest end to prevent a dead short, if so what value ?"
Impossible to say Martin
As you can see from my example below;
If you have many LEDs connected in parallel you may need only a very low value resistor.
I.E 3.9Ω for 32 LEDs on 6V.
But if you fit that as your 'safety' resistor and then test a cct with fewer LEDs you'd probably pop them☹️ If you fit a higher value safety resistor some of your tests with more LEDs may not even trigger.

To be perfectly frank Martin!
I think this comes under the category of 'It seemed like a good idea at the time'!🤔
It would be a waste of your time, a little cash and above all your obvious talents as a model maker and innovator.
My recommendation is 'Do as the big boys do'!
Manufacturers run computer simulations before they fiddle with physical components, or even buy them! It's quicker, easier, safer and cheaper😊
Use the calculator given below and you won't go far wrong, or pop any components👍

BTW: Got curious, so just looked in my resistor rack and found some 3.9 and 8.2Ω 11W and 25W ceramics resistors😁
Used 'em for some audio amp experiments - without upsetting the neighbours😊
Have a few left over (came in packs of 5 and I only needed one or two).
If you're interested I'll add some to your 'Corona Relief Package' 😉
Cheers, Doug 😎

Thank's again Doug.
I am not having much luck in finding a multi-turn pot at the moment.
So i may have to totally re-think this through.

Ref :- Before you switch on to start each test make sure the pot is at the max resistance end and wind back down until all the LEDs trigger.

Should i fit a resister at the lowest end to prevent a dead short, if so what value ?

Martin555.

Parallel is even easier to calculate Martin.
Voltage is same on each LED, current may vary though, and thus brightness!
Taking average values of 25mA and 3V Vf for three LEDs on an 11.1V supply-->
Resistor exact value would be 108Ω. Nearest 'std' values 100 or 120Ω.
See attached calculator link, a good one cos it does series and parallel and shows you the colour code of the nearest 'std' resistor.👍
Many only do series.
http://ledcalc.com/#calc
Disadvantages of parallel arrangements-
1 For parallel arrangements you need higher Wattage rating (bigger) resistors though.
In above case 1W.
2 The wiring in the model gets more complicated, separate earth (-ve) leads to each LED🤔
Makes the wiring bulkier and more difficult to hide.
3 The circuit current is much higher, since you are adding all the individual LED currents.
Thus creating more heat in the dropping resistor and depleting your battery quicker🤔
The one advantage of parallel is that you can connect many more LEDs to a given voltage.
Example: Using your 6V supply and my 'std'/average values (3V and 25mA) you can connect up to 32 LEDs before the supply runs out of steam. BUT you'd need a big, hefty 3.9Ω 3W ceramic resistor to dissipate the ~2.4Watts of heat. Cct current would be 769mA.
Choice is yours😊
If you use a multi-turn pot I think a 1KΩ would do. Would give better resolution.
Maybe a second pot of 100Ω would be better for the lower ranges?
Plus a Range switch!
Before you switch on to start each test make sure the pot is at the max resistance end and wind back down until all the LEDs trigger.
Otherwise maybe 💥😭☹️
Cheers, Doug 😎

Hi Jack,
Thank you.
That is the type of thing i was thinking about.
Most of the LED circuits i tend to do are in parallel.
I will have to see if i can fined something like a ten turn pot.

Martin555.

Hi martin555,

How Odd.

I was just suggesting that for 6V i would just use a 10K pot with 10 or more turns, then once youve got the desired brightness then measure the value of the pot and choose a resistor close to that value.

Like RNinMunich has said anymore than 2 LED's in series and you wont have enough voltage to drive them.

If you have an android device there is an app called electrodroid. its got some pretty useful stuff including an LED resistor calculator.

I hope this helps👍

Jack

Hi jackwatts93,
I have had a notification that you posted but i am unable to fined tour post.

Martin555.

Hi Doug,
Thank you for the information.
This looks like it is going to be a bit more technical than i thought.

I normally test my Led's using two AA batteries that have a resistor in line. (I don't know the value of the resistor as it is covered with heat shrink)

As you have seen on U552 i have a few LED's and i have powered them up using my tester.
So like an idiot i thought all i have to do is make some sort of switch with resistors on it so i could connect up the LED's up and flick a few switches until i get the desired effect then i know ruffly what resistance to fit.
Or maybe turn a variable pot to do the same thing.

Martin555.

Hmm!
Sounds a good idea - at first 'glance' Martin, but-
6V won't get you very far.
Two 2.5V or 3.0 V LEDs and you're done! No resistor needed.
I suspect it would just end up as 'another gadget' to get in the way on the bench.

Calculating dropping resistors for series LEDs is easy anyway, as I've discussed several times here. Mainly in connection with lighting circuits on tugs for various folks.

Basically all you need to do is add up the voltage drop (Vf) on each LED and subtract the total (Vt) from the supply voltage to give the volts to be 'dropped' Vd. If you don't have the data sheets for the LEDs take 25mA as a mid range current (I) and 3.0V as a mid range Vf. Then use R=Vd/I. Attached pics shows typical values for various colour LEDs.
1206 chip LEds may vary! Beware also their Power Rating range: from around 400mW DOWN to only 33mW!!

Example 1: Three NAV lights, Red, Green, White. 11.1V supply (3S LiPo)
Vd=2.1V, 11.1-(3x3), I=25mA or 0.025A.
Therefore R=2.1/0.025 = 84Ω
Next 'standard' value is 82Ω. Or use 100Ω if LEDs are too bright.
See attached Standard Resistor table. Thes values go in decade blocks; e.g. 8.2, 82, 820, 8.2K, 820K etc.
Pw=IV will give you the resistor power rating you need: =0.025*2.1 =0.052W or 52mW.
So a 1/8W resistor would be fine.
If you DO build your gadget, I would use 1/8th Watt 1% tolerance metal foil resistors.
See attached table, type E96. E48 would also do at 2%.
Cheers, Doug 😎

Hi Graham,
My LED circuits are in parallel, but i want to use it on Single, multiple, Series, and parallel circuits.
I only said 6v as it will probably be the voltage used on the finished job.

I have to make it using whatever i can find and i know i do not have any rotary switches.
I do have these two diagrams that i can go by if i end up using the dip switches.
Also i am very limited with regards to electrical components and knowledge.

Martin555.

Hi Martin,

That’s a good idea.
Lots of variables to consider. Voltage, you suggest 6v, but wouldn’t it be useful if it would be useful for higher or lower voltages? Are you just considering a single LED or multiple LEDs in series?

With a single LED, you would probably need a resistance range from 200 ohms to 1000 ohms. This would give a current range from 25mA down to 5mA using a 6 v supply. With several LEDs in series, you would probably need some lower resistance values.

I think the way to do this is to use two 10 way rotary switches. One which would increase the resistance by 10 ohms for each position, and one which would increase it by 100 ohms for each position. That would give you a range from 10 ohms to 1100 ohms in steps of 10 ohms using 20 resistors. I’ll draw out a circuit and post it later (I ‘m off out ‘working’ for the next couple of hours)

Graham93