Deadbugged LED Strobe

89201403972533359 [Steel 9] was looking around for a LED strobe light for reasons unknown. He couldn’t find any that he liked, and when that happened, he did what any normal person would do – make one himself.

[Steel] based this build around a Harbor Freight 27 LED flashlight. This flashlight is just that – a simple switch to turn the LEDs on and off, a button, and from the looks of things, not even a single current limiting resistor. A masterstroke of engineering, surely,

The added circuitry consists only of a pair of transistors, a few resistors, a capacitor, and a pot. Yes, [Steel] is too cool for a 555 chip, It’s just a simple multivibrator circuit and none of the component values are very sensitive.

[Steel] got exactly what he wanted without even having to break out a breadboard. Since he just deadbugged all the circuitry, he’s also reusing the plastic enclosure of the flashlight. That’s a win in any book.

26 thoughts on “Deadbugged LED Strobe

    1. It is definitely the work of the dreaded radioshack single temp pen/soldering gun. I recognize the use of painters tape to minimize cross-soldering anytime I see it and still use it for the IC stuff. We’ve all been there and peeling tape up is way easier than desoldering a little horn on a multipin IC and risking the whole project. Sometimes ya shoot from the hip and it ends up staying like that. Keep on tinkering Steel9 :)
      +1 on hanging garden vs deadbug @pcf11

      1. > It is definitely the work of the dreaded radioshack single temp pen/soldering gun.

        Nah. This is the work of somebody who is either still learning to solder, or just doesn’t give a damn (about the work, the tool, both, etc). Something like that.

        Soldering is a skill and an art; while better tools can help and are convenient – they aren’t the whole story. I have an old soldering iron from when I was a kid just learning – it’s probably worse than today’s “rat-shack single temp” soldering iron – with it I can do a damn fine job. All it takes is care and knowledge of what’s being done.

        Think about it this way: Have you ever looked at a professional soldering jobs done on old tube sets from the 1930s or so? Most of those were point-to-point (no PCBs back then) – very close to “dead bug style”. Do you think they had anything like today’s fancy temperature controlled soldering stations?

        Yet they had no problem building those radios and other equipment – and given the tools and sometimes seemingly tight spots – those assembly technicians arguably turned out works of art. Some of that equipment is still operational even today.

        As in many things in life – it’s generally not the tools, it’s the person wielding them.

        1. How about just a simple no next time? I think you are lecturing the wrong person. Then you, Mr Wizard, mysteriously lose your voice after the “Guns or Butter” speech and give him full pass. smh

  1. Just to clarify dead bug refers to soldering DIP integrated circuits upside down. If your circuit does not contain any ICs then you cannot really use the dead bug construction technique, because you’re missing the bugs. You can call your circuit either point to point, or a hanging garden.

    Here’s virtually the same circuit I made in the early 1980s

    It’s a little worse for the wear and tear today but it still works. It is hanging garden construction.

    1. No pictures, but a mate and I built a similar 2 transistor flip flop on perf board to switch two old telephone relays for “the Oz Machine” for a school play (more time ago than I care to admit, probably around 1980). The machine had a bunch of flashing 240V mains lights on the front, and trundled across the stage on castors with the mains lead trailing behind. I still have a scar on my left arm from slicing myself open spectacularly with a nail we hadn’t quite bashed in far enough. Lots of black tape was all that separated the operator (me) from a 240V zap… I doubt you would be allowed to even attempt such a thing these days, ‘elf and safety doncha know… eletrickery, school kids, trip hazards, it had the lot.

  2. Sometimes when cheap flashlights don’t appear to have current limiting resistors, it’s actually because the carbon glue that glues the less to the body has the resistance. Other times they just put LEDs and batteries in series and try to aim for the right spot on the voltage/current curve of the LEDs.

    1. Well – whatever they did to this HF flashlight, they did it right! I have more than a few of these buggers, and I have yet to have one not work when I needed it – or even for any of the LEDs to go out. They are definitely the cheapest of the cheap, and maybe that quality will or has changed recently (or did in the past). I guess I’ve been lucky with the ones I purchased. I know for most things, HF is terrible. Sometimes, though, there are some gems left around.

      1. The cylindrical 9 LED aluminum flashlights that Horrible Fright carries can develop a number of problems over time. I have them with defective LEDs but the most common problem seems to be the board connection to the aluminum case failing. The board is just wedged into a groove in the flashlight body. There are some solder pips on the board that crush into the groove. If the battery pack smacks into the board it loosens that connection up over time. I have had the switch fail too. I never pulled one of those apart yet to see what happened. I think what might also happen is the aluminum body develops an oxide film and that causes problems too.

        The 9 LED aluminum flashlights are a real pain to take apart. I’ve mounted them in a collet in my mill and used a hacksaw, but the last one I soaked the lens in acetone to soften it, then poked it out with an awl. After that I peeled the aluminum case like a banana with a pair of pliers. I was kind of hoping to dissolve any glue that was used to assemble the flashlight, but it didn’t work that way for me. I think it still worked OK though. From here on in I think that will be my go to method for harvesting LEDs from that style flashlight.

        They’re white LEDs, but they’re not particularly bright, white LEDs. Some tend to have a bluish cast to me too. I guess for nothing I shouldn’t complain. I don’t see how it matters but the black body Harbor Freight branded ones seem better than the blue, or red anodized ones? Besides the finish they look identical to me.

        I have one of the 27 LED rectangular plastic body flashlights too. It still works. Well worth the $2.97 they cost with a coupon. I have a 3 LED B&D flashlight that is much brighter though. I think I need to experiment a bit more with HF’s LEDs to see what they can do. See what kind of current they can take, etc. With no data sheet it will have to be sacrificial destructive testing though I’m afraid. muwahahaha!

    2. Or the LED(s) have a resistor built-in. They’re quite common…and make a lot of sense for situations where you are trying to milk every cent out of manufacturing costs. Eliminates one discreet component.

  3. I’ll just throw this out there. In the same form factor as a 555, you can get a PIC micro. I’m using one right now, in the SO8 package, as a pulse counter and solenoid trigger. Why settle for a single flash mode, when you could have many options?

    Of course, Some Programming Required(tm), but it opens up a world of possibilities in the same form factor, and you can change your mind without getting out the soldering iron.

    1. If you’re going to use a microcontroller, why not go for a 32-bit ARM? </sarcasm>

      I come from a CS background, so using an 8-bit micro is my temptation as well. However, I understand the draw of analog design, and wish I understood it better. Little circuits like this help with that understanding, and there is a beauty in in using the fewest components possible. In that regard, I’m counting the uC not as a single component, but as the hundreds or thousands of transistors that it’s composed of.

      And since you’re starting a flame war, why not use an AVR rather than a PIC? Easier to program (aka cheaper/simpler programmer), more libraries available, bigger user community, hardier IO pins, blah blah blah.

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