How to repair a broken Long Led (and make your own !)

Recently I broke one of my Long Leds, the solid wires were separated from the little connector after bending them a few times…
After searching the internet I found the exact type of connector used:

JST 2-PIN cable #261B, sold including connected wires.

They can be purchased from Adafruit for $ 0.75 each:


Or in Europe from Kiwi-Electronics: https://www.kiwi-electronics.nl/

This is how I repaired my Long Led:
1.
Materials needed:
Broken Long Led
White heat shrink tube appr 6 mm diameter
New JST connector as mentioned above.

Remove the white heat shrink insulation from the broken Long Led.
Now you see a white and a black insulated wire.
Could be a little difficult because the plastic is a littlebit melted together…
One wire should be left a little longer than the other to prevent a short circuit.
Also cut the wires from the new connector different in length.

Solder both wires (Red on white and black on black).

Slide the new piece of white heat shrink tube over the wiring.
It should be as long as the wiring, I used a long knitting needle to push the tube over the Led until the end.

Shrink the white shrink sleeve tube (I used a candle) and ready !

Now you could also make your own long Led with different colors:
Insulate one connection with a small heat shrink tube to avoid a short circuit.
I used black heat shrink tube appr. 2mm.
Apply the same white heat shrink tube as above and you can make green, red or blue Long Leds !




:grinning: :grinning: :grinning:

note:
The light wire and the speaker and the fan and the IR led use the same type of connector, happy soldering ! :grinning:

4 Likes

Very cool stalk collection @alexpikkert!

I believe the resistor in series with the LED is 1000 ohms, so nearly any LED should work satisfactorily. IR, UV, pink, orange …

Some folks may have an old phone charger that uses almost the same jst connector. The one I found had a slightly bigger ridge on it than does the littleBits part. You can just nip that off:

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Hi Chris @chris101,
Indeed the long led is energized via 1000 Ohm on 5V, so it lights up with 5 milliamps. That’s not much, so using bright leds will better. The little JST connectors also seem not really ment to be used for frequent disconnecting and reconnecting, you must pry them in and out with a tool, so I will experiment a little with sandpaper to make it work in a better way, but anyhow, coloured long leds are a fine addition…

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Ah - I don’t have a jst puller, so I just yank 'em out. Shaving off the gripper makes that part easier. The pins provide more than enough friction to hold the stalk in place. And yeah, your color-splash stalks are GREAT! , and a good introduction to bit-modding too. Thanks for posting your easy-to-follow tutorial.

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Hi Alex,

I have a broken long led as well and am very happy I found your detailed explanation. I like the idea of using other LEDs, however I’m not sure what LEDs are compatible. I found an IR led at kiwi electronics that has the following specs:
Doorlaatspanning: 1.35V
Doorlaatstroom: 100mA

Can I connect that LED to the bit the way you described?

Thanks in advance!

Frank

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Hi Frank @cfsl
The Littlebits designers have used different diagrams for the LED bits o2 (long led), o15 (UV led) and o7 (IR led)…
The long led o2 uses an opamp output via a 1000 Ohm resistor, so the maximum current will be appr. 5 milliamps. I think any random led will light up. But maybe your Infrared led needs more current to work, just try it and see if it works in your project, you cannot damage the bit, (thanks to this 1000 Ohm resistor).

The UV led o15 uses a 330 Ohm resistor on the opamp output, so the maximum output current of this bit will be appr 15 milliamps.

The IR led bit o7 uses a switching transistor BC847 which has a maximum load current of 100 milliamps. in the diagram the output current is limited with a resisor of 22 Ohm (?) resulting in a max. current of appr.200 milliamps…(?)

greetings,
alex

Hello @alexpikkert,
You are right about the current of 200mA flowing through the LED.
However, when the bit is correctly used, it should receive a pulsating stream of current, so the IR LED will not be lit constantly.
In comercially made remote controls, the same kind of high pulsating current is used. This makes the remote control powerful to reach long distances to the IR receiver.
The IR LED can stand these high currents, but only for very short bursts of pulsating currents.
So it should be noted that the IR LED bit of littlebits may not be directly used after a switch or slider or any other bit that outputs a constant voltage.
If so, it could destroy the bc817 or IR LED. Uhohh.
It should be placed after an alternating source of current.
Greetings

Hi Frankje @Frankje,
You are right about the bursts.
I checked the IR led with a slider and a switch to activate it with a constant input. It works, the bit is not overloaded or destroyed, the load current is appr.15 milliamps.
the IR led can send audio signals (I tested with the oscillator and the MP3 player) and with a constant input… No problem.

If it can send IR signals from the Arduino IRRemote library is a different question…

Hi @alexpikkert
I just made a test circuit (since I don’t have the IR bit yet ).
It seems when a constant 5V input is fed, the voltage across the 22ohm resistor is about 0.85 Volts. This means that the current through this resistor ( and also through the IR led ) is 39 mA.
And even after a minute or so, the current increases to 41 mA ( the IR led conducts better through heating up).
Can you tell me how you measured 15mA by connecting a switch bit to the IR bit ?
It should be noted that 39mA is too much for the IR led. It will certainly break down after a certain time.
By feeding an alternating current to the IR bit however, it will not get defective, as mentioned before.
Greetings

@Frankje, fyi at least some IR leds can stand 39 mA easily. For example, this one has the following specs: 100 mA continuous, 1000 mA pulse: https://www.adafruit.com/product/387

It is this led I’m considering to use in a project, either connected to the o2 bit, or directly with a resistor through a proto bit (which I would need to buy). Or I can simply buy an o7. Not sure what IR led they use and how it compares to the one mentioned above.

Btw why is the circuitry of the o2 or o7 so complex when essentially one needs a resistor and an led?

Frank

Hi ! Indeed, they’ve probably used an IR LED which can stand higher currents.
And that’s where the transistor is needed. The output of the opamp is not strong enough. The transistor can deliver up to 100mA, as Alex mentioned earlier.

Hi Frank @cfsl and Frankje @Frankje,

My first test of the led currents was done with my self-made power monitor bit, but it seems rather inaccurate for small currents, the display shows steps of 10 mA…
See here: https://littlebits.cc/projects/voltage-and-power-monitor-for-littlebits-version-2

Now I tested the o2 and o7 leds connected to a P1power bit via a protobit with removed connector in the 5V line and my digital ammeter connected in series to this protobit.

I measured the following currents:

o2 bit with standard white led: 2.5 mA
o2 bit with IR led: 3.8 mA

o7 bit with standard white led: 30 mA (oi oi, short test, led shining extremely bright)
o7 bit with its IR led: 41 mA.

Then I tested the capability of sending signals by using power bit-oscillator-led as sender and power bit-light sensor-synth speaker as receiver.
In all situations the frequency from the oscillator could be heard, I think with just minor differences in signal strength (maybe some more testing needed).
:grinning: :musical_score:

The reason for the complex circuitry is to avoid using power from the SIG line (the middle connector from all bits). In every setup with bits you make, the GND and VCC (5V) lines are always in series, submitting power to all bits, and the SIG line takes care of all control and must not be influenced by the number of bits you have in your circuit… :bitstar:

Hi @alexpikkert and @Frankje,

Great data you provided! You’ve convinced me to buy an o7 because I think the current from the o2 bit will be too weak for an IR led. I’ve learned a lot through this discussion, thanks!

What’s a good place to get littlebits in Belgium (or the Netherlands)? Last year I bought them from Bart Smit but they don’t seem to sell them anymore. Do you know of discounts for the holiday season (in other words, should I defer buying)?

Frank

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I buy all my Littlebits from https://www.kiwi-electronics.nl.
They do not have holiday discount I think.
And here you can find all international retailers if you want to buy somwhere else…
http://littlebits.cc/international-retailers
:gift:

ps
If you want to use remote control the other way (sending signals into Littlebits) there is a bit i7 that reacts on any remote control you have , any signal button on a remote will switch this bit fully ON. With a large distance range… :slight_smile:

Hi @cfsl
I live in Belgium and the nearest most comprehensive shop of littlebits is Kiwi electronics. I always order my bits through their online store. They have also a fast delivery.
Greetings