Good Source for Pre-Made LED Circuits

[The14thDr]

I wasn't too sure where to post this, as this could be useful for pretty much any type of build (TARDIS consoles, TARDIS models, or any number of gadgets), but here's hoping that this section is fine.

In my searches on Amazon I found this little LED circuit kit, that includes all of the parts needed for a flashing LED circuit.

https://www.amazon.co.uk/gp/aw/d/B01JBQVTY4/ref=mp_s_a_1_67?ie=UTF8&qid=1470924100&sr=8-67&pi=AC_SX236_SY340_QL65&keywords=led+circuit

One thing I am wondering about is that the kit doesn't include any sort of power source (battery holders, etc.) or switches, so would these have to be bought separately and then wired into the circuit?

Or would it just be easier to buy all of the components separately and wire them up myself?

Kind regards, The14thDr

[galacticprobe]

This wasn't an easy one, for several reasons. First and foremost, as I started this last night, Verizon struck again and decided to take down the system in my area for "maintenance and upgrade" so I lost internet, and they said it wouldn't be back up until morning. Secondly, because for some reason that Amazon UK link wasn't working for me. (I could get to the page, but it was nothing but links and the image of that circuit was really small.) However I did managed to search for the name (Pggpo 5Mm Led Simple Flash Light Circuit Production Board Diy Kit Set) on Amazon US and found several sources for it, some showing better images than others, but each one has the same description of the product and they all list the same components. So here's what I've been able to determine (my comments next to the description, when needed, are in italics):

All have the same Circuit Board size - 2.3cm x 2.3cm square - so it's nice and compact;

Work voltage: 3-14V - this means that a 9-volt battery would be good for powering things in small spaces; if you have more room, a 6- or 12-volt Coleman-style lantern battery would do equally as well since they both fall within the work volt parameters. Also, two 1.5-volt torch/flashlight batteries would also work if connected end to end as in a torch/flashlight because they would give you the minimum 3 volts needed. You can buy inexpensive battery packs for both 9-volt batteries and AA (or any size torch-sized) batteries if using this in a confined space. Just make sure the battery holder pack is wired for use "in series" or you won't get the 3 volts needed; not an issue with the 9-volt battery pack;

Package includes:
PCB board x1 - good news; everything is pre-etched for circuit runs and drilled for the component leads, and labeled on the component side so you'll know where each component goes, and which way it needs to be oriented on the board;
9014 transistor x2 - this seems to be the same type of "pre-amp" transistor as the 2N2222A; the voltage rating is certainly the same, and both are NPN transistors; these are most likely used to drive the LEDs;
LED blue 5mm x2
30K resistor x2 - without having the schematic diagram for this, just going by the component layout on the board, I'd say these are biasing resistors for the transistors, to place the correct voltages on what looks like the transistors' Bases (remembering from other posts that transistors have an Emitter, Base, and Collector - in standard configuration, the Collector is the output, the Base is the input "control valve", and the Emitter is the main current flow path through the transistor from the negative side of the circuit to the positive side via the Collector);
510 ohm resistor x2 - again judging by the location of these resistors on the board, in relation to the LEDs' locations, these are the ballast resistors for the LEDs, which add resistance to the circuit (since an LED is a "short" when conducting), and also control the LEDs' brightness; (if the LEDs are blinding bright, trying a slightly higher value resistor would dim the LED some); these are also most likely the resistors normally found on the transistors' Emitters - sometimes on the Collectors - depending on the circuit it's about 50/50 as to where these resistors will be; if this kit comes with a diagram - and it should - all this will be laid out on the diagram;
22uf electrolytic capacitor x2 - again, without a diagram for the circuit, I can only guess that these are biasing components for the transistors; note that they are "electrolytic", so they are polarized;
Wire x2 - this looks like the input wiring for the board's power; photos to follow.

Here is an image of the board, rotated so some labels are easier to read.


Here are all of the kit components laid out.

(If you open this in a new tab or window you may see it a bit larger.)
You can see the labels on some (like the caps), and the resistance color code on the resistors. (Learning to read the color code is something that takes time to absorb. I'll try to get it into easy to understand terms and post that; but again, there are books in libraries and tutorials on YouTube if anyone wants to look into it while I put my blurb together.) The one thing you can't see are the transistors because they've positioned them face down, and it's on that flat face where you'll find the E, B, and C above the leads corresponding to the Emitter, Base, and Collector. You'll also find the transistor number on there as well.

Finally, here's a look at the kit after it's been fully assembled:

(Again - new tab or window; we all know this drill by now. )
You can see the wiring coming into the board on the left. It almost looks like it's coming into the board from underneath, which means there could have been a plug added with leads for the wires to plug into, or onto, since both ends of the wires have some sort of connector-type cover on them. This would be good for making the circuit more modular, and easy to remove for cleaning and maintenance if one of the components needed replacing.

Now, just because the LEDs are shown wired onto the board doesn't mean they need to be wired onto the board. You can wire them to a remote location with extension wires, just make sure that you get the polarity for the LEDs correct. (You won't get them burnt out if you wire them backwards; they'll just either not light up at all, or light up together if they're supposed to alternately flash. Just... erm... reverse the polarity... on the LED that's connected wrong way round to fix that.)

Which brings me to another "guess". Looking at this board and how it's laid out, it looks like what they've done is taken a 555 timer and "exploded" what you would find inside the chip and used a transistorized circuit to do the same thing - create a "clock chip" for an alternating flasher for two LEDs. There's nothing wrong with that; it just shows you that there are several ways to accomplish the same thing. (Although, when working with a TARDIS console, you have to admit the transistorized version is more befitting what one would expect to find inside an old Type-40 console.)

Anyway, I've rambled on long enough and hope I've been helpful in my babbling.

Dino.

[The14thDr]

Thanks Dino!! This was super helpful (especially for me, as I know next to nothing about electrical circuits )

I'm thinking of buying a few of these kits for various projects, so I'll take more photos of what's inside if anyone is interested.

For the battery packs, would this be the sort of thing I should be looking for?


Thanks again, Dino!! (Seriously, I can't thank you enough for the amount of help you've given me with questions about electronics, etc.)! Thank you!!

Kind regards, The14thDr

[galacticprobe]

You're more than welcome, 14th. It's my pleasure. That battery pack you've posted would work if it's wired so the batteries are in series, meaning that they're essentially connected end to end so when you put a volt meter to the wires, you get 3 or so volts, which is the minimum needed to run the circuit. (Most of those "1.5 volt" batteries - when new - will actually have a little more voltage in them, so you could see around 4 volts from that battery pack.)

They also make packs and snap-connect contacts for 9-volt batteries, which is also well within the operating limits of the circuit.


Here's one of the 9-volt battery boxes. It's just a little larger than the battery, but it makes things easy for using the 9-volt battery (which would probably last longer than the two AA batteries). Some of these boxes even come with little "On/Off" switches in them.


And here's the snap connector version. No option for a built-in "On/Off" switch with this one. You'd have to wire in your own and the battery would have to be velcroed in place, or otherwise secured. Of course you'd have to secure the box above as well, but at least you could stick the velcro directly to the box and not have to worry about it when it came time to replace the battery. With this snap connector, of you had velcro on the battery, you'd need to cut a new strip of velcro every time you replaced the battery because half of the velcro would go in the bin with the spent battery.

There are several ways of using velcro to secure these battery packs in place so you'd just have to experiment to see which way works best for what you're using it for.

And as always I hope this was helpful.

Dino.

[The14thDr]

Thanks Dino, as always this was very helpful.