Flashing Light Unit

[galacticprobe]

Okay. I just watched that video and this circuit will work on any voltage between 4.5 and 16 (the working voltage range of the NE555 Timer chip), so the 12V battery (or a wall adapter) will work with it. As for one of those things that recharges mobile phones? I'm not sure. I would need to know the max. current output of one of those because if the bulb draws more current than what that charger can put out, the charger will burn out; the same goes for the wall adapter. A 12V battery like the small ones used in Coleman-type lanterns (or two 6-volt batteries in series to make the 12 volts) will also work; so will a brick-sized battery like the kind found in back-up power supplies and motorized wheelchairs. Pretty much any 12 volt battery, or combination of batteries that totals between 4.5 and 16 volts. (Since most car bulbs are of the 12 volt variety, I would stick to 12 volts.)

For using this circuit to flash something like a car's turn signal bulb or a side-marker light (which is the same as one of the dash board lights), that 2N2222A transistor will be fine (the 2222 is almost as bullet proof as the NE555 timer). If you want to play it safe in case you're worried about the transistor overheating if using a turn signal bulb (which pulls more current than a dash or side marker light), you can always substitute the transistor with a 2N3055; it's a larger transistor and can easily handle a turn signal bulb without breaking a sweat. (Another of the old reliable, almost bullet proof electronic components.)

That 1,000 micro Farad capacitor (seen on diagrams as 1,000 uf) in this case is an "electrolytic" capacitor, meaning that it is polarized; it has a positive and negative side, as opposed to the standard "cap", which isn't polarized. With the electrolytic caps, you have to be careful when connecting it that you do not reverse the polarity (where have I heard that one before?) or the cap will explode like a firecracker. They do make variable caps, so you can substitute one of them for this electrolytic cap, and then you can use a small screwdriver to adjust the cap for a fading rate that suits your eye.

For the flashing rate, I would substitute a variable resistor (a.k.a. potentiometer, or "pot" for short) for the 1,200 Ohm (also seen on diagrams as 1.2k, or 1.2k Ohm, or 1.2k - Omega, the symbol for Ohms). Again here you can use a small screwdriver to adjust the rate to your liking, which is better than having to change out the resistor each time you want to try a different flash rate. You can also use a higher value pot if you want to slow the flash rate down even more, and even a 5k (5,000) Ohm pot can be adjusted down to 0 Ohms, just like any pot can, so you've got a wider range of Ohms to adjust through which in turn gives you a wider range of flashing rates.

The 150 Ohm resistor is the "ballast" resistor so the LED doesn't short the circuit. To the circuit, and LED (or any diode), when current is flowing through it looks like nothing more than a piece of wire, so the resistor is needed to "put the brakes on", so to speak. This resistor can be eliminated if you're using a bulb instead of the LED because the bulb's filament (that tight springy thing you see inside the bulb) has its own natural resistance, and it's that resistance that builds up the heat which is given off as light (as things get hot, they start to glow, and when they cool down, the glowing fades away). Another thing to note is that a bulb, unlike an LED, has an inherent "fade in/out" due to the heating up and then cooling down of the filament. So with this circuit, you could find the bulb's fading is a bit slower than normal for the bulb due to having that cap in there. (This is why I would suggest using a variable cap to control the fade time; if the bulb fades fine on its own, you can just adjust the cap down to its minimum, or just eliminate the cap altogether, replacing it with a simple wire.)

The rest of the circuit is straight forward as explained in the video, and this guy explains it extremely well. I think just about anyone can draw out a wiring diagram if they use the old "Pause" control as the vid progresses step by step. The same goes for drawing a schematic diagram from this (which I'll work on, and then post it here to show how all of these components connect together). I'll draw it as the vid shows it in case some people want to use a high-brightness LED, and also modified for use with a car turn signal or dash/side marker bulb.

It might take me a day or so to draw things up, but I will get it posted as soon as I can.

Dino.
P. S. How's that, Nate?

[warmcanofcoke]

That is amazing Dino. Good advice, and well explained.

I was looking at one of the batteries I mentioned before. Made by PNY Model: T2200 Li-ion Battery  - Capacity: 2200mAh/8.1Wh Output: USB 5V= 1A

So I could use a series of these to equal 15V. Just under the 16V you mentioned.

What is you opinion on using a step-up transformer? Like this one: Pololu 12V Step-Up Voltage Regulator U3V12F12 https://www.pololu.com/product/2117

Could I use the one 5V Battery with this unit? Or should I stick to Double A batteries and forget about this thing?

[galacticprobe]

I took a look at that step-up gizmo. Their numbers are a little confusing, and they really don't explain the operation in much detail. With things like this you have to take into account more of the Ohm's Law equations:

E(Voltage)=I(Current) x R(Resistance) In this, E is the constant and has to be balanced by the other two factors. So if you're stepping up E, and R (the circuit) stays the same, then I has to be lowered.

The other equation is the "PIE", or P(Power, in Watts)=I x E. In this one P is the constant. So if your input voltage is 2.5 (min. as it says on that web page) with an input current (I) of 1.4 Amps, you've got a power level of 3.5 Watts for that circuit. Then if you step up that output to, say, 12 volts, to keep the Power constant at 3.5 Watts, your current is going to drop to roughly 0.3 amps (0.279 amps). That wouldn't be enough to drive a car's side marker light.

Putting the batteries you mentioned in series to get a 15 volt output would be fine for the flasher circuit since the NE555 can handle it, as can either the 2N2222A or 2N3055 transistors, but then you have to remember that you'd be flashing a 12 volt bulb, and those extra 4 volts would burn the bulb out almost instantly. What you would need to do is place a variable "pot" in the circuit where the video says to place the 150 Ohm resister so you could adjust it to give you only 12 volts (or 11 volts for a bit of wiggle room) to the bulb. That, or put a 7812 regulator (that's a 12 volt voltage regulator) on the input between the 15 volts and the flasher circuit. Then you can forget about that pot and not have to worry about adjusting it for 12 volts to the bulb because the 7812 voltage regulator automatically does that for the entire circuit. (I can draw that out while I'm working on the diagram as described in that video.)

Believe me when I say there is more to electronics than the average person thinks: Power levels, Voltage, Current draw, Resistance of the "load" (the thingy being powered - in this case the car bulb)... even though it looks simple (which I'll admit the circuit is), the factors that go into making that simple circuit work without blowing up aren't as simple.

I hope this hasn't caused any discouragement; it was intended to be educational, and I hope it helps everyone understand how things work a little better.

Dino.

[warmcanofcoke]

No this has been an educational experience. Also, I'm accessing some memories from my college years, as I can follow the thread of the conversation. 

[Rassilons Rod]

Dino.... I wonder if this is a US/UK difference. I learned it as V=I x R..... Where V would be the same as your E.

Interesting

[hb88banzai]

I was taught it as V = I x R here on the west side of the US as well (along with P = I x V for computing Power), so don't think it's a US vs UK thing.

Does E perhaps stand for Electrical Potential in this particular usage? It usually designates Energy, in physics at least, which is a bit different.  East Coast vs West Coast, or perhaps just an idiosyncrasy of professional training? Makes me curious as well, regardless.

[Rassilons Rod]

I had P=IV too.

[galacticprobe]

I'm not sure where the difference comes in, but in electronics school (at least also in most of the electronics books they gave us to read and teach from in electronics school, including a several-inch thick book written by a guy named Schrader), E was used for voltage because it was short for "Electromotive Force"; I was short for a French term meaning Current Intensity and named so by the person who discovered current flow (I can't remember his full name, but he was French and his last name was Ampere, which is where the term Amp (or Ampere) comes from to denote the amount of current flow, and why Amp meters (or Ammeters) are labeled in Amps, or milliamps for low current. R, well, Resistance is sort of self-explanatory.

I'm not sure why there is a difference in the labelling of voltage (E vs. V), especially when you consider the person that discovered the Volt was Alessandro Volta. Across the pond I can understand there being a difference, as in US gas (gasoline) vs. UK petrol; or the US vacuum tube is a UK valve, etc. But from US east coast to US west coast? Now that one has scrambled what's left of my brain, especially when you consider that the Coast Guard moved our ET (Electronics Tech) School from Governors Island, NY (east coast) to Petaluma, CA (west coast), and all military electronics training is standard.

It could have to do with a difference in the type of training; even in the military (where all services are virtually identical with training), we have headaches between ETs and EMs (Electrician's Mates). ETs are taught that current flow is the excess of electrons flowing from the negative source towards a positive source, whereas EMs are taught that current flow is the positive Proton particles flowing into the "holes" (the negative source) left by electrons. But since current flow is the flow of negatively-charged electrons, then it only makes sense that current flow is from the excess of negative to the lack of negative (positive). Not so to EMs; to them it's just the opposite.

So, I guess, long answer summed up... I have no idea why there is a difference between E vs. V.

Dino.

[galacticprobe]

Back on the "Flashing Light Unit" front:

I've been working on that circuit as described in the video, and I've got several versions of it (starting with exactly how the vid describes things). The post I've got planned for it is going to take a little longer than I've got in me tonight. (Today was the day from hell; aside from another vertigo episode it was "Hell's Bells" from the word go; on a scale of 1 to 10, with 10 being 'someone just dropped a fully functioning TARDIS on my front porch' and 1 being 'my house is surrounded by Daleks on the left, Cybermen on the right, Slitheen blocking the front, Clockwork Droids looking for spare parts in the back, angry Silurians burrowing their way through from underneath, and a Sontaran Battle Fleet overhead'... today was a -5!)

So with luck sometime tomorrow I'll have a nice post ready to go so everyone and anyone can get their lights flashing to their satisfaction.

Sorry for the delay.

Dino.

[galacticprobe]

Sorry once again for the delay. I'm still working on this. This day from hell isn't letting up (still in the -5 range on that scale from 1 to 10), but honestly, I'm working on this so anyone can use the circuit for - well - any flashing light they want to use. I really was hoping that I'd have it all ready for posting tonight, but life has gotten in the way like a razor ribbon wire fence! (Another point to illustrate just how much reality sucks!)

I'm giving myself an end of the week deadline to get my post up. If I haven't gotten it up by then, I'll just post my address, and the member living closest to me can come over to my house, string me up, and beat my like a piñata!

Dino.

[warmcanofcoke]

No rush. Take the time you need. We are interested in making the circuit. I've ordered a set of 12v 1000uf capacitors from Russia - oddly hard to find the 12v variety on eBay... 35v , 16v, 10v, 40v etc easy peasy lemon squeezy.

But just so you know, your health comes first.

[galacticprobe]

Thanks, Nate. And the 12V caps are somewhat difficult to find as in most circuits the designers err on the side of "a little extra for safety". Most 12 volt circuits use caps that are 16V or higher just to make sure the cap doesn't blow if the voltage drifts a little over that 12V working voltage. (As in most US car electrical systems, the alternator puts out 14 volts to charge the battery while also running the car's systems; even the bulbs for the lights are actually 14-volt bulbs.)

So for using a 12-volt power source, a 16V cap is the better choice. What has the effect on how the cap charges and discharges (and what controls the flashing/fading rate) is the Farad value; a higher value cap will give a slower fade than a lower value (i.e. a 1,000uf cap will fade an LED/bulb much slower than a 100uf, but much faster than a 10,000 uf cap, regardless if the cap is rated at 12 volts or 36 volts; in variable caps it's the Farad value that you'd be adjusting, and usually it's the max. f value that's shown on diagrams).

Caps are touchy things. If they're polarized and you install them with the polarity reversed, they'll explode. If they're rated for 12 volts and you charge them to 13 volts, they may also explode, though it may take them a few minutes (constant charge), and then they may not explode (varying charge, like in the fader circuit).

I once had a student working for me, and he rebuilt a transceiver that we had problems with. The thing worked fine when we powered it up for testing. So just to be sure, we left it running for a while to break it in. He'd sworn that he'd double checked everything as he was reassembling the transceiver. Unbeknownst to me, the "polarized" main filter cap (one about the size of the cardboard tube at the center of a toilet paper roll), he'd installed with its polarity reversed. And because the cap was so large (physically and electronically) that it ran fine for about 30 minutes or so. (It took that long for the reversed polarity to overload.) Suddenly I heard what I would best describe as the sound of a phaser on overload.

I looked around the room (which was about 18 feet wide and 40 feet long), and finally zeroed in on the transceiver on the workbench at the far end of the room - about 35 or so feet away from my desk). I saw the flash. I heard what sounded like a small cannon going off (so did half of the building!). And I saw this transceiver launch itself about three feet off of the workbench and towards my face! (I dropped behind the desk and heard the crash as the transceiver landed on the floor in the center of the room.) The transceiver weighed about 25 pounds, so that cap, when it blew, had some serious force to it. (The student rebuilt the transceiver - again, this time under closer supervision - and the thing worked like a charm.)

The size of the cap in this fader circuit would never blow with that much force - I think I said in an earlier post it would be like a firecracker - so there wouldn't be that much to worry about: only having to rebuild the circuit board. The negative side of those electrolytic (polarized) caps is clearly marked so getting the polarity right won't be a problem. Just try to keep the source voltage at or just under 12 volts and you should be just fine.

Dino.

[warmcanofcoke]

Very interesting anecdote. I'm lucky to have also purchased some 16v 1000uf caps as well .... at the time I had suspected I had made a mistake in ordering them, and sought out the 12v variety as replacements. Now, I still haven't purchased the potentiometers for the circuit to adjust the flashing rate, or the resister to finish off the circuit. I expect I'll receive the bulb and the caps and the timing circuits later in the week. Take care my friend.

[galacticprobe]

Thanks again, Nate. Things are starting to settle out, albeit a little more slowly than I would like them to. Still, I'm working on that diagram as I can, and also a narrative so people know what they're looking at, and have some helpful hints to use while building the circuit.

Dino.

[galacticprobe]

Well, here it is (at long last): the light flashing circuit. I watched the video several times just to make sure that I had all of the connections as described in the vid correct. I've got the circuit diagram showing everything just as the person making the vid has his wired, and looking at it from the electronics theory of it, this circuit as wired shouldn't work, but obviously as seen in the vid, it does. (Sort of like a bumble bee that shouldn't fly, but does.)

He mentions in the vid that he's "modified" the circuit from its original design, so for giggles I followed his link and looked at the original:

In this version the circuit is designed to alternately flash/fade two LEDs, and this could come in quite handy for people trying to replicate the alternate flashing red LEDs of the beryllium clock chip from the McGann console. (You'll have to experiment with the values of the cap and the 20k Ohm (kilo Ohm, or 20,000 Ohm) resistor to get the alternating flash as close as possible to what we saw on screen, but that shouldn't be a problem if you replace those components with variable ones; the cap should control the fading, and the 20k potentiometer ("pot") should control the timing. This large value would be good for the pot because it gives you a very wide range of timing to play with.) The 150 Ohm resistors connected between the transistors and the LEDs control the brightness and also act as a "brake" because the LED, like any diode, is just like a piece of wire when it's conducting and without that "ballast resistor" would short out the circuit, so some pots in there wouldn't go amiss as you might not always find two LEDs with the same brightness levels, and with pots you could adjust for that.

You'll notice in the above circuit the arrows of the LEDs and the transistors point in the same direction, and this is normally how the circuit should be wired. (Current flow is always against the arrow - don't ask why, I'm not an engineer and didn't invent these components or design their symbols, so I can't answer that one.)

A quick lesson in basics:

Whenever you see lines in the diagram cross with a black dot in the intersection it means those lines are connected, so when building the circuit those wires (and components) are wired together.

When you see lines cross with no dot in the intersection it means those wires are not connected.

While explaining the diagram above I mentioned those arrows in the transistors and the LEDs (or any diode, actually; LEDs are just diodes that put out light, and that's indicated by the arrows - straight or wavy - "emitting" from the diode symbol). Those arrows always point to the negative lead of the component; in diodes it's the cathode, in transistors it depends on the type, but the arrow will point to either the Emitter (as in the one labeled "NPN") or the Base (as in the one labeled "PNP"); in both of those cases the "N" is for "Negative" and the "P" is for "Positive".

The capacitor symbol shows the positive side, but on the actual component - depending on the manufacturer - it will show either the positive side with a +, or the negative side with a -. (Non-polarized caps won't have any such markings.) Also, the cap symbol may or may not have the curved "plate", but that doesn't really matter; it's all dependent on who draws the diagram and with all of the equipment I've worked on, I've seen it done both ways many times. The important thing is to look for the + on the diagram, and either the + or - on the component. When working with adjustable caps, you'll want to use a proper Tuning Tool to make adjustments. A cap is basically two thin metal plates (these could be as thin as foil) separated by paper, air, or some other non-conductive (dielectric) material, and a charge builds up between the plates, and then discharges through the circuit (which is what makes that LED fade in and out). If you use a metal jeweler's screwdriver to adjust a variable cap, the metal in the screwdriver will affect the cap's value; that is, the cap will think the extra metal is part of it and you'll get an erroneous fading of the LED or bulb, and the fade will change when you take the screwdriver away. A Tuning Tool is mostly plastic, with just enough metal on the tips to be strong enough to turn the adjustment screw, and that won't affect the cap's value so you'll get a more accurate fade as you make adjustments.

Resistors or pots aren't polarized, so no need to worry about those. There's also no need to worry about the metal in a jeweler's screwdriver adversely affecting the value of a pot since the pot is constructed of completely different material than a cap. I won't go into the color code for the stripes on the resistors that tell you what the Ohms value is; it would be easier to look or ask for the value you need (it would be written on the package), and then just keep the resistors in their respective packages until needed. (Not meaning to insult any technical people here, but I'm trying to make this as easy as possible for everyone, especially those with no electronics experience.)

Counting pins on the IC (Integrated Circuit) Chip: The chip in the diagram above shows a "U"-shaped notch at the top; this is the orientation notch and normally only seen on the component itself, though some circuit designers draw it on the symbol if the pin layout is exactly the same as it is on the component. On chips that have the notch Pin 1 is always the one closest to and to the left of the notch when looking at it from the top. Some chips will have a small "dimple" instead of a notch, and that dimple will be right next to Pin 1; in both cases it's referred to as the "locator notch". The pin numbers run straight down the side from Pin 1 to the last pin (in this case, Pin 4), and then starting with the next number (in this case Pin 5) up the other side to the last pin on the chip.

So enough of the basics; now, on to how the circuit is described in the video...

I've drawn this circuit exactly as described in the video. As you can see by looking at the arrows on the LED and the transistor, they're pointing in the opposed directions - which is why I say from an electronics tech's viewpoint, this circuit is a bumble bee. But... in the video it works just fine so I'm not going to overanalyze it.

And while it's not mentioned in the vid what voltage his battery was, I've drawn this circuit running off of 12 volts like from a car or smaller motorcycle battery, or even one of those gel cell batteries you'd find inside a computer's uninterpretable power supple (or UPS) so car bulbs can be used in the circuit. As described, the cap C1 controls the fade time (how long it takes the LED to light up and dim out), and R1 controls the fade rate (how long it will be between "flashes"). It would be good to have these as variable components so you can experiment with different values without having to change out the components. The circuit should work fine without the transistor Q1 since the NE555 Timer Chip can easily handle running an LED, but as you can see from the original circuit, this one has been modified enough, so let's restrict any other modifications to just making R1 and C1 variable. Power supply connections are easy; the positive side of the battery is indicated by the "+12V", and the "-V (Ground)" is the negative side. Also, going by the size of the resistors in the video I've labeled them as 1/2 Watt; they could be 1/4 Watt - it's hard to really tell - but 1/2 Watt would be easier to handle as 1/4 Watt would he about half the physical size of a 1/2 Watt.

Now to make this circuit work with a car bulb (side marker or turn signal):

(You'll notice I've got some * in the circuit. I'll get to them soon.)
This circuit is basically the same, only I've substituted the symbols for pots for R1 and R2, and a variable cap C1. Adjusting those components will do the same as in the above mentioned circuits (though I doubt R2 will be needed unless you're using a bulb that's less than a 12-volt bulb - say a 6-volt bulb; then you'll need that resistor to adjust things so the proper voltage reaches the bulb).

Bulbs have an inherent fading of their own due to their filaments having to heat up before they put out any light, and then as the filament cools down, the bulb has a natural fade to it. Still, if you want more of a fade to the bulb, this circuit will certainly do that for you.

In this case here, you  will definitely need to use the transistor as the bulb will draw more current than the 555 Timer can handle. This way the transistor acts like a traffic bypass; it lets a little current flow through the 555 Timer, while diverting most of the current through itself to flow through the bulb.

I've also left out the wattage on the resistors because you might need larger than 1/2 Watt for R2 if you use a resistor there. R1 should still be good at 1/2 Watt because not much current will flow through it, but if after a short bit you feel what you think is too much heat coming off of R1 when you put the back of your finger near it (DON'T TOUCH IT!), you can always replace it with a 1 Watt, which is the next size wattage up. And when you're working with pots that are of higher wattage, you're probably going to be using those larger, round ones that are adjusted with knobs rather than jeweler's screwdriver or tuning tool. So keep that in mind when picking out the project box you'll be building this circuit in.

Which brings me to the first *. The transistor you use will depend on the type of bulb you use. If you're using a car side marker light (or a dashboard light - they're the same bulb most of the time), then a 2N2222A will work fine.

This is the standard "spade base" dashboard/side marker bulb (at least on most US cars). It's rated at 14 volts, so the 12-volt supply won't tax it, and it has a max. current draw of 270mA (milliamps). The 2N2222A can handle a max. current of 800mA so this sort of bulb is well within that parameter. (And this is where the ** comes in.)

If you use a side marker bulb with a "bayonet base"...

then you may need the larger 2N3055 transistor I've mentioned in other posts. This type of bulb draws up to 1.8 Amps of current (that's 1,800mA - well above the 2N2222's limit). If you're using a turn signal/brake light bulb, then you could be pulling between 2 and 5 Amps depending on the bulb. The 2N3055 may be a bit overkill since it can handle a max. current of 15 Amps, but you'd never have to worry about it overheating and burning out.

The two transistors are both general purpose amplifiers; they have a very different appearance to them, but in both cases E=Emitter, B=Base, and C=Collector:

This is the 2N2222A. As seen in the video it's rather compact, and I've drawn it here larger than actual size for clarity. The markings on the side of the case are pretty much standard. The little "locator tab" on the casing is closest to the Emitter, with the Base in the middle and the Collector on the other side (which I believe is attached to the case, so if you have to test it with a meter you can just touch the meter lead to the case). Also remember that so you don't accidentally touch the case when the circuit is running.


This is the big honking' 2N3055 "power transistor". It's still a general purpose amplifier, but it can handle much more current. This one is drawn close to actual size. There is no locator tab on this type of casing. Instead, the location of the leads on the transistor tells you which lead is which. Looking at the bottom you'll see the two leads are off to the side. Holding it as I've drawn it, the Emitter is going to be the "top" lead and the Base is the Bottom lead. The case itself is the Collector (so again, be very careful when working around this one while the circuit is running, especially if you're using a larger bulb that pulls more current). The markings on the top of the casing are pretty standard; the "AAWW" is the month and year of manufacture, and the "XXX" is the three letter code for the country of manufacture.

When wiring this transistor into the circuit, you'll have to use screws to hold it to the circuit board (hence the screw holes built into the casing). So to connect the Collector wire, simply wrap the wire around one of the screws, or attach a loop terminal lug to the wire (sorry I don't have a pic of one of those, but I can find one if someone needs to see what it looks like), and then slip the screw through the lug and tighten it to the case. As I said, this one might be a bit of overkill, being able to handle up to 15 Amps, but it will never overheat even if using both filaments in a brake/tail/parking light bulb. And if you're using one of those, then you definitely want to use a pot for R1 to adjust the flash timing, and a variable cap for C1 for the fading time because those larger bulbs might not need any additional fade thanks to their natural filament fade.

The longevity of your battery will depend on what type of "light" you use. Bulbs will naturally draw more current than LEDs, and thus drain the battery faster, and larger bulbs will drain the battery faster than smaller bulbs. Of course, if you've got a +12-volt power supply that has enough current output and can plug into a wall outlet, then there's nothing to worry about (provided you've got a way of getting the power cord from the wall outlet into your TARDIS... or console).

And that's about all I can think of for this circuit. It will work well with either bulb, or even one of those "LED stalks" from a modern Coleman-type lantern. In any case I've got both circuits here for anyone to use, copy, distribute, etc. to anyone that's looking for such a circuit. (And of course, the original circuit whence these came from so someone can try it out for that beryllium clock chip). The person making the video didn't mention where that original circuit came from, so if anyone recognizes it and knows who deserves the credit for it, please let us know.

If anyone has any specific questions about the circuit, or thinks of something I might have left out, just ask away and I'll do my best to answer them.

I know this was a long one, but I hope people find it helpful.

Dino.

EDIT: One thing I forgot to mention while writing this is that it's a good idea to use sockets for the "active" components when wiring up the circuit board, namely the IC Chip and the Transistor. Those are the components that do all of the work (aside from the LEDs or the bulb, but those will presumably be outside of the circuit box, and in sockets of their own). This way you can wire in the sockets, and just plug in the 555 Timer Chip and the Transistor. Then if one should fail you just have to unplug it, and plug in the replacement without the hassle of de-soldering and re-soldering. (And while the NE555, 2N2222A, and 2N3055 are all pretty well "bullet proof", there is always the possibility that one could fail - they are all made by Earthlings - so it's better to err on the side of ease of replacement.)

The socket for the chip is known as a DIP socket (Dual In-line Pin) and come in various sizes, so just ask for an 8-pin DIP socket; also while wiring things on the circuit board, it would be a good idea to mark Pin 1 of the IC Chip socket on the circuit board with a dab from a paint pen, just so there's no confusion if you have to replace the chip. For the transistors, ask for a small transistor socket for a "twenty-two-twenty-two type"; for the larger one, ask for a "power transistor" socket (and specify a "thirty-fifty-five type" if you happen to be dealing with a pudding brain). You'll still have to secure the 3055 transistor with screws, but the rest of it will be plug-in once the socket is soldered in place.

There: now hopefully I haven't forgotten anything else!