I found this very interesting energy harvesting set up today http://qrp.gr/energy-harvesting/ I found the 0.082v start up piticularly impressive. Almost as low as my lowest starter. Which needs germanium transistor to start from 0.06v and around a milli amp (Video here). I think this is the first evidence I have seen of silicon transistors starting under 0.3v though, and most of the ones I have in silicon that start low, need more than a milli amp to start, so not really any good as energy harvester. For me a good energy harvester will start anywhere under 0.5v and not need a full milli amp. preferably run on micro or nano amps. While being capable of supplying charge to a AAA or greater. I have about 4 oscilators that can do this. The ones that start really low (under .4v standard silicon limit) mostly need near the full milli amp to run, some of the higher starters, in the 0.4-0.6v range, can run on a micro amp or less. as long as the input can be measured in nano watts I'm happy. Low milli watts can be ok too.
So the above site really got my attention... Its showing a really nice output waveform too. So I would like to do a replication, or variant with another depletion jfet.
It brings to my attention (again) my poor level of transistor knowledge. I guess I am doing ok, a year ago I could hardly get npn transistors to do what I wanted. Now I have them pretty mastered, and am getting better with pnp's and n Chanel mosfets. Of which I have been able to salvage lots of. Gone are the days of saving up for weeks to get a $12 transistor, only to have magic smoke on the first day. Now I pull transistors out of stuff I find in bins, and they rarely let out smoke (unless I want to "See what it can take" so no accidental smoke would be more accurate) Cant say I have found too many j fets though. Or any depletion mode fets. I have an atlas dca55 semiconductor tester, which can save a lot of time googling serial numbers. But I can only recall one occasion of finding a jfet. I think from a plasma tv?
So what stuff am I likely to find in bins and on nature strips, that could be a source of depletion mode jfet's or other depletion fets? I still have a lot of boards from Plasma tv's that I have not got round to de-soldering, should I look more there? Or is there some other common appliance I would find these parts in? I have a stack of VCR's DVD's audio amps and other common household stuff, as well as all the parts from 4 rear projection tv's and an 8 foot high stack of microwaves. (My Daughter says I'm not allowed to collect any more broken things till I sort out what I have) Surely there is bound to be a few depletion fets in there somewhere? SMD is ok, although through hole wold be preferable. I have a really bad habit of breaking legs off the smaller smd transistors making dead bug circuits. Its a real bugger to solder them back on when broken inside the case... I only have about 50% sucsess rate where the transistor doesn't get cooked...
So the above site really got my attention... Its showing a really nice output waveform too. So I would like to do a replication, or variant with another depletion jfet.
It brings to my attention (again) my poor level of transistor knowledge. I guess I am doing ok, a year ago I could hardly get npn transistors to do what I wanted. Now I have them pretty mastered, and am getting better with pnp's and n Chanel mosfets. Of which I have been able to salvage lots of. Gone are the days of saving up for weeks to get a $12 transistor, only to have magic smoke on the first day. Now I pull transistors out of stuff I find in bins, and they rarely let out smoke (unless I want to "See what it can take" so no accidental smoke would be more accurate) Cant say I have found too many j fets though. Or any depletion mode fets. I have an atlas dca55 semiconductor tester, which can save a lot of time googling serial numbers. But I can only recall one occasion of finding a jfet. I think from a plasma tv?
So what stuff am I likely to find in bins and on nature strips, that could be a source of depletion mode jfet's or other depletion fets? I still have a lot of boards from Plasma tv's that I have not got round to de-soldering, should I look more there? Or is there some other common appliance I would find these parts in? I have a stack of VCR's DVD's audio amps and other common household stuff, as well as all the parts from 4 rear projection tv's and an 8 foot high stack of microwaves. (My Daughter says I'm not allowed to collect any more broken things till I sort out what I have) Surely there is bound to be a few depletion fets in there somewhere? SMD is ok, although through hole wold be preferable. I have a really bad habit of breaking legs off the smaller smd transistors making dead bug circuits. Its a real bugger to solder them back on when broken inside the case... I only have about 50% sucsess rate where the transistor doesn't get cooked...
