| Recently I looked at an old 3-LED VistaLite rear light and thought about chucking it and buying one of the new VistaLite Super Nebulas, a 5-LED light which is supposedly even brighter than their previous 5-LED light (the one with the silver plastic reflector behind the LEDs). But I decided to try to upgrade the LEDs on it instead. The circuit board is easy to get at, you just remove a couple of screws and you can flip it over to look at the backside. Looking closely at the circuit board, I found that the power tracks were parallel and the LEDs straddled it, and there were holes for 5 LEDs! I went to Maplin and bought some Hyperbright and Extreme brightness LEDs. The Hyperbright ones had a 30 degree viewing angle and light output of 3.5 candles, and the Extreme brightness ones an 8 degree viewing angle and light output of 7 candles. Installing the new LEDs was easy. Both the LEDs I took out and the new ones had a flat edge, so I put the new ones in so the flat edge was the same place as flat edge of the old ones. The Hyperbright ones were both brighter and had a wider viewing angle than the ones that were in it before. A definite win. I installed one Extreme brightness LED, but it had such a narrow viewing angle that most of the time it weren’t contributing anything to the light output. So I removed it. Still curious, I went back to Maplin, wanting to try out their 60 degree (1.5 candle) Hyperbright LEDs. I bought a few, but was a bit disturbed to find out that they had three legs and a completely round top. The shop guy said that they were basically two LED devices stuck into one clear plastic package. The Maplin catalog says that the LEDs share a common cathode (not that that means much to me) so there were three legs, not four. So I had to figure out how to install three legs into two holes. I compared the metal bits inside the LED with a standard LED and figured out that the middle leg (the shared leg of the two devices, which was the longer leg) hooked up to the same part as the longer leg on the normal LED, and on the normal LED this leg was opposite the flat part of the LED. So I soldered the two outside legs of the 60 degree LED together, and cut one of them off. I soldered the LED into the circuit board with the remaining side leg attached to the place I’d put the flat parts of the normal LED, and the longer middle leg on the other side. (The Maplin catalog says that the 60 degree LEDs have a common cathode, and they also say that the cathode is the part marked with a short lead and the flat spot on a normal LED . However, the shared leg of the 60 degree LEDs was definitely the middle leg, and it was longer, and it clearly corresponded with the longer lead on the normal LED. So they’ve got something wrong there!) And it worked! I found out that the LED is 60 degrees in one direction only — it puts out a beam that’s much wider than it is tall. This is what you’d expect from two LEDs side by side, and it’s perfect for LED rear lights, since you need more side-to-side visibility than up-down visibility. The plastic bit of the LED is wider in one dimension than the other, so you can figure out how to install it so the wideness of the beam is oriented in the right direction. Although the 60 degree LED has a lower brightness (candlepower) than the 30 degree LEDs, its much wider viewing angle increases dramatically the angle at which you can see the VistaLite, making it a clear win. Happy with my results on the old VistaLite, I went to butcher the other ones (I have quite a collection of VistaLite rear lights!). I discovered that the LEDs used in the 5-LED lights that include the silvery plastic reflector are identical to the 30 degree Hyperbright ones, so it wasn’t any use replacing those. Still, it was worth taking one or two of them out and putting in 60 degree ones instead to improve the viewing angle. The LED butchery went along fine until I came to the last VistaLite I had. I opened this one up to find that its LEDs looked like they were soldered in backwards! The flat spot on the LED was opposite the flat spot printed on the circuit board. So what was happening here? Were the voltages flipped around on this circuit board, or did it have strange LEDs, with the flat spots on the opposite side? I didn’t want to experiment with my last 60° LED, so I used one of the too-narrow Extreme brightness ones. I first put it in so its flat spot lined up with the flat spots of the other LEDs. It didn’t work. I then took it out and reversed it, so the flat spot lined up with the flat spot printed on the circuit board. And then it worked. Which meant that the voltages of the circuit board were normal, it’s just that the LEDs installed in it had the flat spots opposite the place they normally were. So I then installed the 60° LED the way I had in the other VistaLites, with the side leg soldered next to the flat spot on the diagram and the longer middle leg soldered on the opposite side. Success. I think the moral of this story is, if the circuit board has any printed diagrams, put the longer leg opposite the printed flat spot. I took a look at a Cateye LD500 I had around to see if I could upgrade that, but the circuit board seems solidly soldered into place, so I gave up. If you feel like upgrading your VistaLites (or any other LED light where you can easily get at the back of the circuit board) the Maplin part numbers are: CH22Y for the 60 degree Hyperbright ones with 3 legs UK20W for the 30 degree Hyperbright ones with 2 legs For further details visit Myra’s bike page at http://www.cl.cam.ac.uk/~mvi20/bike/index.html |  VistaLite with new LEDs. The 60 degree LED is the one in the middle, and the other ones are the 30 degree ones.  Bare LEDs. The top one is the 60 degree Hyperbright LED and the bottom one the 30 degree Hyperbright LED. The middle (longer) leg of the 60 degree LED clearly corresponds with the bottom (longer) leg of the 30 degree LED.  Beam pattern of modified VistaLite. I held the modified VistaLite abour 1" from the wall to get a picture of the beam pattern it makes. The 60 degree LED in the middle clearly has a much wider beam than the other 4 LEDs.  Looking straight at VistaLite with light on. This shows that viewed from staight on, the 60 degree LED looks more or less like the others.  Looking at the VistaLite from the side. However the middle LED clearly improved the side viewing angle! |
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