Answers to questions you could or should you be asking....
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Age Considerations (v:1.0 March '10)
Bare & Twist (v:1.0 March '10)
Connecting to a 12v Power Supply (v:1.0 March '10)
How to fit a Car Plug (v:1.0 March '10)
How to fit a Power Socket (v:1.0 March '10)
How will I Power my Kit? (v:1.0 March '10)
If Your Circuit Doesn't Work (v:1.0 March '10)
Insulation (v:1.0 March '10)
LED legs (v:1.0 March '10)
LED tester ('AA') (v:1.0 March '10)
LED tester (12v) (v:1.0 March '10)
Parallel Circuits (v:1.0 March '10)
Rechargeable Batteries (v:1.0 March '10)
Recommended Equipment (v:1.0 March '10)
Resistors (v:1.0 March '10)
Resistor Power Rating (v:1.0 March '10)
Safety Instructions (v:1.0 March '10)
Series Circuits (v:1.0 March '10)
Short Circuits (v:1.0 March '10)
Soldering (v:1.0 March '10)
Soldering LEDs (v:1.0 March '10)
What is an LED? (v:1.0 March '10)
12 Volt Batteries (v:1.0 March '10)
Some of our knowledge pages are less authoritative than others due to incomplete understanding on the part of your author.
I apologise for any omissions and / or mistakes.
If you find you can either suggest corrections / clarifications or would like to re-write the page so as to be more useful to us all (which will be credited and have links as appropriate), please contact us.
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How will I power my Kit
How will I Power my Kit? The answer is easy if you think about where you want your circuit to be used.
If you want to make it easily portable then you should build something that runs off 'AA' rechargeable batteries. We supply 'AA' kits with a battery box that holds 4 batteries. The battery box can be in a pocket or a hat, hidden in your artwork... wherever. Small wires to your LEDs can be totally hidden too.
If you are intending to use your LEDs anywhere fixed, then 12 volts is the way to go.
If you are in a small off-grid, solar or wind-powered home, you'll probably have 12v.
If you are in a vehicle then the available power is usually 12v (but make sure to ask someone who knows unless you are certain).
Sometimes vehicles have a 24v system... fear not, drop us a line & we'll recalculate your kit for you so as to run at the higher voltage.If you are living anywhere with mains power you will need a mains 12v adapter, which we can supply.
You could use an old vehicle battery if you can get hold of one. This will need to be charged form time to time. Have a look at '12v Batteries' for more information.
To Sum Up...
If you want to be totally portable, small & easily hidden, look at 'AA' kits.
For everything else, you should look at the 12v kits.'AA' kits are totally self-contained (although you will need to buy some batteries) but you may need some pointers as to how to link your kit up to 12v.
©LEDfantastic.com 2011 BACK
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Age considerations
Age-ism in LED Kit Land
Whilst there are always exceptions to any rule, we suggest that any of the kits on our site are unsuitable for any child under the age of 7 or 8. This is due to the small size & fiddliness of the parts and the level of concentration required.
With close supervision I'm sure your bright youngster could accomplish the easier kits but also you'd stand a good chance of putting them off for life...
In the best traditions of nanny-state-ism I think I have to say;
'Unsuitable for children under the age of 36 months. Contains Small Parts'
At the other end of the spectrum, please be aware, again, that the parts are small and may be difficult to put together without good light and a decent magnifying system if you are far-sighted.
©LEDfantastic.com 2011 BACK
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Bare & Twist
Use a wire stripper or small knife to strip away a small part of the insulation at the end of the wire.
If you are using a knife try putting the wire on a hard surface then gently rolling the knife over it where you want the insulating cover to be cut. If all the surface is scored then the plastic covering will usually pull away quite easily.
Wire strippers are a lot less fuss and save a lot of time if you are doing many wire-stripping operations.
This will leave the fine metal wires exposed. They may already be neatly twisted around each other, but usually not.
An easy method to get this twist is to hold the bare wires between thumb and two fingers of one hand & gently roll the rest of the wire between finger & thumb of the other hand. Let the bare wires rotate a little, but apply just enough pressure so they twist into one piece.
This makes them much stronger & easier to deal with.©LEDfantastic.com 2011 BACK
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Connecting to 12v
Connecting to 12v
12v Mains Adapter Power Socket How to fit a Power Socket
12 Volts comes from a battery or from a mains adapter.
The battery may be charged from the mains, a vehicle's alternator, solar panels or a wind turbine.
Find out more about 12v Batteries.MAINS ADAPTER
If you are using a mains powered 12v adapter then you can either cut the small plug off at the end of the adapter wire and 'bodge' your own connection or you can get hold of a socket to plug the adapter into.
If you get an adapter from us then the plug to fit is also available. We can't promise that other adapters will fit our plug, but bodging is an honourable solution...
Connector Block Terminal Block
WITH THE POWER PLUG SOCKET...
See 'Fitting a Power Socket' for more detail... or...
BODGE THE ADAPTER...
Cut the plug off the end of the wire furthest from the body of the adapter, to give yourself as much spare wire to play with as possible. But it's always sensible to leave 10cm of wire connected to the plug in case you want to use it later.
Bare & Twist the cut ends then either:
Twist join them to your circuit wires, check they are connected correctly, solder then insulate (for a permanent join), OR
Use 2 sections of a connector block and join the adapter wires into the female side and the LED circuit wires into the male (for an adaptable, easy connect join), OR
Use 2 sections of terminal block for a semi-permanent join.
IF YOU ARE CONNECTING DIRECT TO 12 VOLTS...
Big Crocs Mini Crocs Car Plug How to fit a Car Plug
Your options will most likely be...
Soldering or using terminal blocks to connect to wiring that already exists (you should be familiar with the electrics you are going to use);
Using Big Crocodile Clips to connect direct to the battery terminals;
Using Small Croc Clips to attach to small contacts inside old light fittings;
Using a 'Car Plug' to fit into a cigarette lighter socket.
The 'Car Plug' is the most elegant and you can see how to wire it up here.
Solder your wires direct to Mini-Croc Clips or screw your wires to Big Croc Clips.
Remember, LEDs only let electricity flow in one direction - but won't be damaged if you connect them backwards. Just fit your croc clips and swap the terminals you connect them to if the circuit doesn't light up.©LEDfantastic.com 2011 BACK
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Circuit not working?
If Your Circuit Doesn't Work...
The most likely problem is that you have the current going around the circuit in the wrong direction. The LEDs will only let the current travel in one direction. Reverse the + and – wires.
If your circuit still doesn't work when you've tried connecting it both ways round then its a fair bet that you've connected one or two of your LEDs the wrong way around. Check the leg lengths, look for the small cut-out on the edge of the LED lens or carefully look at the insides of the LEDs – they should all be oriented the same way.
Still not working? – check for short circuits and make sure all your joints are secure.
Finally check each LED individually (don't forget to use the resistor) to be sure you haven't damaged them.
Still stumped? Drop me a line detailing the problem.
©LEDfantastic.com 2011 BACK
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Insulation
If you make one of the circuits described on this site & it lies on the table with none of its wires touching, you probably won't need any insulation.
If you are going to use your LEDs in a practical manner, they will probably take a bit of a bashing and inevitably bare wires will touch. If this 'short-circuit' means the current can bypass the resistor, you will ruin all your LEDs.
If the short-circuit bypasses an LED, the other LEDs will receive too much power and burn out fairly quickly.
Electrical insulation tape is easy to find & pretty cheap. Don't use more than is needed to cover the bare metal, but make sure all parts are covered.
More tape can be used to join already wrapped pieces together.
Other tapes may work just as well ('gaffer' or 'duct' tape for example) but are often painfully difficult to strip off if you make a mistake.
Make sure your circuit is working properly before you add the insulation.
©LEDfantastic.com 2011 BACK
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LED legs
LED legs are somewhat fragile. They will take a bit of abuse but will snap if you don't look after them. If you repeatedly wiggle LED legs they will usually snap just where they enter the LED itself, making the LED pretty much useless.If you want to bend the legs on purpose, nip the legs tightly between finger & thumb halfway down their length. Then use your other hand to gently bend the leg. If you bend the legs here too much & they snap, you've still got enough leg left to solder onto.
©LEDfantastic.com 2011 BACK
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'AA' LED Tester
In your kit you will find a second resistor that you don't need to make your kit.
This resistor enables you to hook up your LEDs individually to 4.8v without overdriving them. It should have a label* that tells you it is for the tester.Here's what you do:
Bare the ends of the battery snap connector.
Twist one of the wires of your resistor around the end of the red wire of the battery snap.
Make sure the red & black wires are not touching or you will
short-circuit your batteries.
Insert 4x 'AA' rechargeable batteries.You can now test your LEDs. Touch the resistor wire to the long leg of the LED and the black snap wire to the short leg. The LED will light up, unless it's broken. Try touching the wires the other way round, then check your batteries before deciding your LED is dead.
*If you loose the label or it's not there, this is how you identify the resistor you need, it will be dark blue or brown. The blue resistor has 5 stripes which are, in order, brown, black, black, black & brown. The brown version has only 4 stripes, which are gold, brown, black and brown. This is a 100 Ω (ohms) resistor.
©LEDfantastic.com 2011 BACK
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12v LED Tester
In your kit you will find a second resistor that you don't need to make your kit.
This resistor enables you to hook up your LEDs individually to 12v without killing them. It should have a label* that tells you it is for the tester.
Here's what you do:
Cut three bits of wire - two that are 10cm long and one 20cm.
Bare & Twist all the ends.
To each end of the resistor connect one of the 10cm wires, twisting the bared ends around
the resistor's wires.
Solder the joints.
Connect one of the resistor-joined wires to the positive of your power supply.
Connect one end of the bared 20cm length to the negative of your power supply.
Make sure the wires do not touch each other or you will short-circuit your batteries.
Switch on your power supply.
Touch the bare resistor wire (positive) end to the long leg of the LED and the end of the
20cm wire to the short leg of the LED.
Your LED will light up, unless it's broken.
Try touching the wires the other way around, then check your batteries before deciding your
LED is dead.
*If you loose the label or it's not there, this is how you identify the resistor you need:
It will be dark blue or brown. If it is blue it will have five stripes which are, in order, brown, black, black, purple (very dark) & yellow. The brown version has only 4 stripes, which are gold, brown, purple and yellow (nearly invisible). They are both types of 470 Ω (ohms) resistor.©LEDfantastic.com 2011 BACK
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Parallel Circuits
The diagram represents a parallel circuit. If we think of it as a ladder, the power flows down either side of the ladder and the load (in our case LEDs) are the rungs.
This means that each LED gets the same current. The resistor sets the current level for each individual LED.
This type of circuit is mainly used when the supply voltage is low, for instance in our 'AA' battery kits.
Parallel circuits are only viable when all the LEDs used are of the same (or very similar) characteristics. They can only be guaranteed to work properly if you use the same colour LEDs.
Also note that the resistor is more likely to overheat in this arrangement than a series circuit - it has to deal with (in the above case) 3 times as much power as it would if the circuit only had one LED. This is not a problem in small arrays with a few LEDs, but once you get above 6 or 8 make sure you test the resistor for heat before building it into something flammable. This problem can be largely avoided by using a resistor with a larger watts (power) rating.
If you want to learn how to calculate resistance values for LED circuits go here.
©LEDfantastic.com 2011 BACK