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| Wondering about recycling of electronic power adapters |
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| Konkedout:
The media has frequently mentioned the proliferation of excess old power adapters. And the EU has pushed for standardization around USB-C. I do not like USB-C so much because it seems too small and flimsy. Maybe good for a smartphone but not so much for bigger things such as a laptop. But that is not where I am going with this. I have my own collection of old power adapters. Many were my own and a bunch were the result of dumpster diving when I worked at a well-known company. In my experience, these things usually outlast whatever they were powering. For some years now, I have a laundry room "dimlight" powered by a power adapter from an old cordless phone. This has four 1W white LEDs but each one is running at about 15 mA. Our laundry room has no windows, and this light allows walking through (and other quick basic actions) with doors closed and without having to turn on the overhead fluorescents. For hobbyists and anyone who likes to tinker with electronics, many of these power adapters are worthwhile! They handle the risky part of powering your electronics; that is the AC/DC power conversion and isolation. I particularly like laptop power adapters, which typically provide 18V - 20V at 40W - 200W. Those make a very useful starting point to produce other voltages. So often on this forum, a novice wants to do AC/DC power conversion. That is a bad idea for anyone (even me who has designed many AC/DC power supplies) to do as a hobby project. Does anyone have any experience or thoughts about old power adapters being dropped off (and separated out) at recycling centers, so that hobbyists etc. can pick them up for free? |
| Zero999:
I don't know about recycling centres, but I know they're available from many charity shops for a low price. Somewhat off topic: have you tried changing the feedback divider to get different voltages? |
| Konkedout:
In theory that ought to be possible in some cases. The power adapter in my dimlight is unregulated with a mains frequency transformer. I do not remember the ratings, but with load current far under the rating, the output voltage is much higher than the rating. So I do not expect any regulator IC or feedback divider in that one. I assume that many of the older/smaller units may be similar. Second is that most of these power adapters are sealed shut. Either they are glued or ultrasonically welded. Third; whether it is a linear or switching power supply, the transformer (and maybe other aspects) will limit the range for any adjustment. I guess that adjusting an 18V converter down to 12V might not be too difficult if you can figure out the schematic and layout adequately. |
| magic:
Flyback switchers are tricky to convert because peak primary voltage and auxiliary supply for the PWM controller are determined by output voltage times transformer turns ratio. You may blow things up or simply cause it not to work if you don't know what you are doing. Small adjustments are straightforward, though. |
| CatalinaWOW:
I do the same, but there are some things to think about. 1. "It handles the risky part..". In principal yes, and probably pretty well on supplies that were associated with higher end gear like laptops. But the low end wall warts were often somewhat dodgy. Just be aware of this and don't make unwarranted assumptions. 2. They are no less susceptible to drying/failing electrolytic capacitors than any other gear and much more difficult to repair. One experience I had. A supply for my security camera system failed and I drug out a replacement from my bin. Same specs as the failed unit (voltage and current rating). But it didn't work at all with the security cameras. Checked voltage with my DVM. Spot on. Wasn't until I got the oscilloscope on it and found that the output filter had totally failed. Under load it was going to zero and about twice nominal output at the line frequency. No clean way to open it up and repair so I added an external filter and it is in service now. 3. Some of these require a minimum load to operate. They will shut down if the load they are expecting isn't there. |
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