标签: flashlight

Over time, I have developed a horror of replaceable, single-use batteries. I'm not particularly a greenie, but it just seems to be an incredible waste when rechargeable batteries are available. The LED torches you get these days are much more efficient battery users, but when I saw these LED torches in a local store for only $5 and bought a few, I still wanted to make them rechargeable, off a 12 V supply.   They use the square 6 V lantern batteries with the springs on the top. You do see rechargeable ones, but they're hellishly expensive. I'd picked up a box of these boards that someone was chucking out. Each board had five rectangular 400 mAH NiCd cells, a PCB, and some components. I'd removed and used some of the batteries in other projects. Those batteries were made by Sanyo and if there's one thing Sanyo do well, it is make rechargeable batteries. But could I use them for this project?   I took apart an old lantern battery to see what I could do with it. It had four compartments with one large zinc-carbon cell in each, each of which I removed. But if I removed two of the dividers, my Sanyo NiCds just fitted lengthways into the larger compartment. By forming them into 6 V packs consisting of three cells on top of each other and two vertically, I found I could fit 10 of my packs into a modified empty lantern cell case. That's 4 AH of battery, albeit in small chunks. The remaining space in the top of the battery pack was minimal. But I love challenges like this...   I decided I wanted the sharing components and a charging circuit inside the battery. Sharing is easy. Each battery pack had the negative terminals tied together, and a Schottky diode (to minimise voltage drop) from its positive terminal onto the common positive terminal. For charging, I worked on the principle that when it is charged, a NiCd will approach 1.5 V per cell. I used a 7809 regulator to give a 9 V supply, with a standard diode (0.6 V drop) and a 33-Ω resistor in series to each battery pack. If the cell is at 1.5 V, the charge current will be (9 – 0.6 – (5 x 1.5)) / 33 = 0.9 V / 33 Ω = 27 mA, well below the 1/10 C – 40 mA in this case—that is safe for trickle-charging a NiCd. If the battery is discharged, say at 6 V, the current would be larger, around 72 mA. The result was a fast initial charge tapering off to a low rate, which is safe if you leave it on for days. Since the battery packs had the Schottky diodes going to the main positive terminal, I thought I could use the positive terminal for charging as well. This was my circuit:   The small space left inside the top of the battery meant I'd have to use surface-mount components, something I'd never done before. More challenge. I got some SMD diodes, resistors, and regulators really cheap off Element 14's bargain pages and designed a PCB around them. The battery springs were mounted to the case with rivets. I drilled these out and used small bolts and nuts to connect them to—and securely mount—my PCB. I had a fair bit of PCB real estate available due to the small size of my SMD components, so I used some for a heat sink for my regulator.   Everything just fit inside the battery case. I used a couple of layers of plastic to separate the batteries from the PCB. The components were on the other side from the batteries but the bolt heads protruded through. I did not want any shorts. The torches worked well. I get a good few hours of light out of them on a fully charged battery. I did find a couple of minor problems: * The battery is not short-circuit proof. I did inadvertently short one once. It blew a PCB track under a diode, but no components. I have since modified the PCB to have a constriction in the main track away from any diodes, so if it does blow it will blow there, where it's at least accessible. * The batteries showed a far higher than expected self-discharge rate. Although there are diodes that stop the individual batteries discharging into the regulator, I failed to notice that the main common positive line goes, through a diode, to the regulator input. The 7809 regulator will not work with 6 V going into it, but it will draw a quiescent current. I kind of like it when this happens. It shows me that I'm not as smart as I think I am... * Fortunately I included a link on the board (LK1 In the schematic) so that the 12 V charging source can be connected separately. I opened the link and took a wire outside the battery. I could take this to a socket, but will probably put a couple of contacts on the body of the torches and build a charging bay for them. * When the batteries are very flat, the regulator tends not to give the full 9 V out. I found this was due to my regulators being the M type, which limit at 500 ma, though this wasn't stated when I bought them. It's not a problem, since it only limits the charge current delivered to a flat battery pack and as it charges the regulator very soon starts regulating correctly again. These batteries were not rated for fast charging, so this limit is probably a good thing! All in all... Cost: Less than $10 per torch. Running cost: almost nothing. Satisfaction: Priceless! Don Tavidash s ubmitted this article as part of Frankenstein's Fix, a design contest hosted by EE Times (US).  

I typically can't help myself when it comes to fixing things, especially electronics. My better half returned from a bargain-hunting day with a wind-up flashlight and charger she found for a dollar in a thrift store. She said she wanted a flashlight for an upcoming camping trip and a charger for her cell phone that she could use out in the wild. My wife loves a bargain, so she was pretty pleased with herself and asked me to help her hook up the charger. Unfortunately, she was disappointed when nothing seemed to charge. I had to investigate; I hate things that don't work. After some exploration I discovered the output was only 3V. Maybe that was why it was found in the thrift store. In her typical style she threw the offending item in the garbage, rolling her eyes in frustration. As I said, I can't help myself when it comes to fixing things so I picked it out of the trash and had a little look to see if I could diagnose the problem. I thought I could add a boost circuit to get it to 5V, but I didn't have the parts. I added it to the mountain of unfinished projects that used to be my desk. Eventually, the day came when I couldn't ignore Mount Electronica any longer, and I embarked on an expedition to the desk. Not long into the tidying session, I discovered an LED light bulb I had bought for the kitchen a while ago. I had made the rookie mistake of not checking the voltage that was required and picked up a 12V bulb instead of the one I needed. It had joined the pile and now it distracted me from my chore. I decided to strip out the 1W LED from the bulb for another project. Inside I found an MC34063 IC. Checking the datasheet, as we geeks do religiously, I identified it as a Step-Up/Down Regulator that was being used to step down 12V to 3V. I started work on transforming it to a step-down straight away. Lady Luck was smiling on me that day as the datasheet had an example, which meant that all I needed to do was pick the right resistors. The circuit needed to change completely, so out came the breadboard. After some cavalier soldering to mount a few of the surface mount parts, I was up and running. I'd only used two resistors extra to the original parts from the bulb. After the initial success I just had to cram it into the flashlight and I was done. On cracking open the flashlight I realised that I didn't have much room to spare. The breadboard simply wouldn't fit. Undeterred, I decided that a little PCB design was needed. I knocked together a single-sided board and mounted it on top of the existing PCB in the flashlight, placing the components to fit inside the curved case as best I could. I had no idea if it would actually fit or whether this last hurdle would be the one that tripped me. With a PCB etched and all of the components soldered, I fired up the converter for one final test before hacking it into the case. It worked like a charm, first time! The voltage out was as close to 5V as I was going to get: Now it was time to get it into the case. Unfortunately, Lady Luck was looking the other way. The case just would not close. A closer inspection gave me some hope. The PCB could potentially shed some excess weight. I took a deep breath and sanded down the PCB as close to the components as I dared and trimmed the wires as short as they could possibly be. I gave it another try. The case closed. It fit perfectly. All that was left to do was connect the switch and the winder, and I was on the home stretch. Then came the moment of truth: Would it actually charge? With the cell phone connected, I cranked the handle, building up speed and hoping for the best. Success! The charge light came on. I had done it. But it wasn't all good news. The flashlight wasn't quite what it once was, as the boost converter was draining the capacitor. It now needs a crank before every use. It's a small price to pay, though. One day I may do a rewire, but for now, my work is done. I had transformed the charger that didn't make the grade into something that actually worked. Sadly, it was a little late for the original camping trip by the time I had finished. Brice Harris is a father of three, husband of one, and he enjoys seeing things work. Together they raise backyard chickens and make maple syrup. He submitted this article as part of Frankenstein's Fix, a design contest hosted by EE Times (US).  

I have developed a horror of replaceable, single-use batteries over the years. I'm not particularly a greenie, but it just seems to be an incredible waste when rechargeable batteries are available. The LED torches you get these days are much more efficient battery users, but when I saw these LED torches in a local store for only $5 and bought a few, I still wanted to make them rechargeable, off a 12 V supply.   They use the square 6 V lantern batteries with the springs on the top. You do see rechargeable ones, but they're hellishly expensive. I'd picked up a box of these boards that someone was chucking out. Each board had five rectangular 400 mAH NiCd cells, a PCB, and some components. I'd removed and used some of the batteries in other projects. Those batteries were made by Sanyo and if there's one thing Sanyo do well, it is make rechargeable batteries. But could I use them for this project?   I took apart an old lantern battery to see what I could do with it. It had four compartments with one large zinc-carbon cell in each, each of which I removed. But if I removed two of the dividers, my Sanyo NiCds just fitted lengthways into the larger compartment. By forming them into 6 V packs consisting of three cells on top of each other and two vertically, I found I could fit 10 of my packs into a modified empty lantern cell case. That's 4 AH of battery, albeit in small chunks. The remaining space in the top of the battery pack was minimal. But I love challenges like this...   I decided I wanted the sharing components and a charging circuit inside the battery. Sharing is easy. Each battery pack had the negative terminals tied together, and a Schottky diode (to minimise voltage drop) from its positive terminal onto the common positive terminal. For charging, I worked on the principle that when it is charged, a NiCd will approach 1.5 V per cell. I used a 7809 regulator to give a 9 V supply, with a standard diode (0.6 V drop) and a 33-Ω resistor in series to each battery pack. If the cell is at 1.5 V, the charge current will be (9 – 0.6 – (5 x 1.5)) / 33 = 0.9 V / 33 Ω = 27 mA, well below the 1/10 C – 40 mA in this case—that is safe for trickle-charging a NiCd. If the battery is discharged, say at 6 V, the current would be larger, around 72 mA. The result was a fast initial charge tapering off to a low rate, which is safe if you leave it on for days. Since the battery packs had the Schottky diodes going to the main positive terminal, I thought I could use the positive terminal for charging as well. This was my circuit:   The small space left inside the top of the battery meant I'd have to use surface-mount components, something I'd never done before. More challenge. I got some SMD diodes, resistors, and regulators really cheap off Element 14's bargain pages and designed a PCB around them. The battery springs were mounted to the case with rivets. I drilled these out and used small bolts and nuts to connect them to—and securely mount—my PCB. I had a fair bit of PCB real estate available due to the small size of my SMD components, so I used some for a heat sink for my regulator.   Everything just fit inside the battery case. I used a couple of layers of plastic to separate the batteries from the PCB. The components were on the other side from the batteries but the bolt heads protruded through. I did not want any shorts. The torches worked well. I get a good few hours of light out of them on a fully charged battery. I did find a couple of minor problems: * The battery is not short-circuit proof. I did inadvertently short one once. It blew a PCB track under a diode, but no components. I have since modified the PCB to have a constriction in the main track away from any diodes, so if it does blow it will blow there, where it's at least accessible. * The batteries showed a far higher than expected self-discharge rate. Although there are diodes that stop the individual batteries discharging into the regulator, I failed to notice that the main common positive line goes, through a diode, to the regulator input. The 7809 regulator will not work with 6 V going into it, but it will draw a quiescent current. I kind of like it when this happens. It shows me that I'm not as smart as I think I am... * Fortunately I included a link on the board (LK1 In the schematic) so that the 12 V charging source can be connected separately. I opened the link and took a wire outside the battery. I could take this to a socket, but will probably put a couple of contacts on the body of the torches and build a charging bay for them. * When the batteries are very flat, the regulator tends not to give the full 9 V out. I found this was due to my regulators being the M type, which limit at 500 ma, though this wasn't stated when I bought them. It's not a problem, since it only limits the charge current delivered to a flat battery pack and as it charges the regulator very soon starts regulating correctly again. These batteries were not rated for fast charging, so this limit is probably a good thing! All in all... Cost: Less than $10 per torch. Running cost: almost nothing. Satisfaction: Priceless! Don Tavidash s ubmitted this article as part of Frankenstein's Fix, a design contest hosted by EE Times (US).

This has been a long week and I'm in for a bit of a laugh... Have you seen the "Missing Missy" thread on the 27bslash6.com website? This is really hilarious. According to a short piece in the Reader's Digest, art director David Thorn was asked by his demanding coworker Shannon to design a poster for her missing cat, Missy. This thread follows a series of posters that he sent her, along with her responses ( Click here to see the full thread). You know all the "Blond" jokes that go around that are usually unkind to ladies with blond hair? Well, I just saw a funny definition: "Blond Joke – A joke so simple even a man can understand it!" Actually, this month's Reader's Digest is jam-packed with interesting tidbits of trivia and nuggets of knowledge. Take the American martial artist and actor Chuck Norris, for example. It seems that as a result of his "tough guy" image, there's an Internet website called Chuck Norris Facts that ascribes various implausible or even impossible feats to Norris. For example: * Chuck Norris is so fast that his GPS speaks to him in the past tense. * Chuck Norris can strangle you with a cordless phone * Chuck Norris knows Victoria's secret But my favourite is "Superman owns a pair of Chuck Norris pyjamas." Actually, speaking of favourites, there was a really great joke (yes, it was in this month's Reader's Digest – how did you guess?). I live in the Bible Belt of America, which means that there are an incredible number of churches of every conceivable denomination. Bearing this in mind, the joke goes as follows: Once I saw a guy on a bridge about to jump... Me: "Don't do it!" Him: "Nobody loves me." Me: "God loves you." Him: "Do you believe in God?" Me: "Yes." Him: "Are you a Christian, Jew, or Muslim?" Me: "I'm a Christian." Him: "Me too! Are you a Catholic or a Protestant?" Me: "I'm a Protestant." Him: "Me too! What franchise?" Me: "I'm a Baptist." Him: "Me too! Northern Baptist or Southern Baptist?" Me: "Northern Baptist." Him: "Me too! Northern Conservative Baptist or Northern Liberal Baptist?" Me: "Northern Conservative Baptist." Him: "Me too! Northern Conservative Baptist Great Lakes Region or Northern Conservative Baptist Eastern Region?" Me: "Northern Conservative Baptist Great Lakes Region." Him: "Me too! Northern Conservative Baptist Great Lakes Region Council of 1879 or Northern Conservative Baptist Great Lakes Region Council of 1912." Me: "Northern Conservative Baptist Great Lakes Region Council of 1879." Him: "Hmmm, I'm Northern Conservative Baptist Great Lakes Region Council of 1912." Me: "Die heretic!" And I pushed him off the bridge. While we're on a religious theme, did you hear the real-life story about the Dutchman who is recreating a massive version of Noah's Ark to biblical proportions? ( Click here to see the full article article.) I love playing with LEDs, so I must admit to drooling a little when my chum Brian emailed me with a link to a YouTube video about a guy who has built himself a 500-LED Extreme Flashlight. And speaking of YouTube, my chip Alan in the UK sent me a link to a video of some water fountains in Dubai . This particular display is accompanies Time to Say Goodbye with Andrea Bocelli and Sarah Brightman: Do you know, I could keep this up for hours, but the weekend is calling me and I have a bunch of stuff to do before I can answer its siren song, so I must away...