The power of junk

[@Xynudu]

UPDATE: I later reduced the generator pulley diameter to increase the RPM and am now able to get a maximum output of 3.15 volts AC and 2.70 DC with the Tarot Stirling engine. The pulley ratio is 2.8 : 1. Under load the engine is spinning at 770 RPM and the generator at 2156 RPM. This is within the design limits of the PC case fan. Cheers Rob

[@flyingshards595]

That's really cool!

[@kreynolds1123]

@@Xynudu given just over 400 milivolt drop it appears your using schottkey diodes that individually have between 200 to 300 milivolt forward voltage drop. Considering the low voltages here efficiency diode recitification is terribly inefficient. Have you ever heard of active rectification or synchronous rectification using mosfets as "ideal diodes" ?

[@Xynudu]

I only know a bit about bridge rectifiers. I don't profess to be any sort of electronics guy, so mosfets are way out of my league. Cheers Rob

[@shawnmcauliffe5072]

It's only junk until someone repurposes it and then boom, not junk.

[@kreynolds1123]

If you measure 2.5v ac, that's the rms (root mean square) voltage. The peek voltage can be calculated by rms_voltage × square_root_2, roughly 1.4142. The diode loss then is about 700 milivolt per diode and full wave bridge rectifyers always have at least 2 conducting diodes, which means the diodes are dropping 1.4v. 2.5vac×1.414(peek conversion)=3.535v(peek) 3.535v peek - 1.4v rectifyer = 2.135v peek pulsed dc 2.135v / sqrt 2 (converting peek to rms = 1.51v dc ripple rms. Since the diode loss is a significant portion of the generators output voltage, rectifying the output voltage waste a lot of the little bits of power being generated. You could use that transformer to bump up the ac voltage which would make the diode drop a smaller fraction of the output voltage so that you can get more of the power into a load rather than just heating diodes. 😊 Add a little capacitor to smooth the rectified output could hold output a little higher longer. Making the LED shine a little longer making it appear brighter with our persistence of vision.

[@Xynudu]

Thanks for that. I did think about adding a small capacitor to smooth the output. I have a few and will see how it affects the LEDs. This is only an experimental/educational exercise for me, so I don't expect any long term use out of this. Still very interesting when you think what I started with :) Cheers Rob

[@RetroSteamTech]

Nice one Rob 👍👍 You will get 400mV to 700mV drop across the rectifier depending on how much current you are drawing. If you attach the multimeter to the output from the rectifier and then connect more lights you should see this. I bet thousands of those wall wart powers supplies get dumped, so recycling the parts is a great idea. I even used the little transformer from one for a project once. Cheers, Alan.

[@Xynudu]

Hi Alan. I was going to build a small rectifier as I have a bundle of suitable tiny diodes, but then I though hang on what's in those useless low output DC power packs. Luckily I had one that was about to be binned, many are AC, and open heart surgery revealed treasure :) Not much voltage to play with, but enough. I could probably get another half a volt out of the genny if I tried bumping the speed, but I've proven the concept and will leave it there. That Stirling engine has really had some use lately and is a great machine. Good little project that kept the brain active. Cheers Rob

[@SeanBZA]

@@Xynudu You can use the fine wire in the transformer, and rewind the stator of the motor with more than double the number of turns of wire, and get a higher voltage.

[@Xynudu]

Wouldn't that would put extra load on the Stirling engine, which is already pretty much maxed out ?

[@SeanBZA]

@@Xynudu No, so long as you do not draw extra current, but a higher voltage will allow you to compensate for the diode drop. Best though to hunt up some 24V fans though, as they come with the more turns of fine wire already.

[@j.f.christ8421]

AC to DC isn't quite that simple. First up is the AC measurement is RMS (sorta like the average), rectifying it gets you the peak voltage. To get the peak you multiply RMS by the square root of 2 (1.4), so Rob's 2.8 VAC becomes 3.9 VDC. Then you drop 2 diodes (~1.4v) to get the 2.5 VDC shown on the meter. There's no smoothing capacitor so you're going to get some nasty 100Hz ripple, that'll cause the voltage to drop with higher loads.

[@ianlulham]

It's very hard to throw anyting away and this demonstrates why

[@Xynudu]

Yes Ian. I'm kicking myself over all the low output DC power packs I've tossed into the recycle bin over the years. Anything with less than 1 Amp output always got the toss. LOL What a waste. Cheers Rob

[@m8e]

The peak voltage of AC will be a bit more that the measured voltage. (Peak should be 41.4% higher than measured RMS voltage) When you rectify, you should get close to peak voltage, minus voltage loss of rectifier. 2.5V is perfect for charging 2 NiMH cells. (1.25v per cell)

[@Xynudu]

Thanks for that. I'm no electronics guy, so this is useful info to me. Cheers Rob

[@MrFactotum]

great to make something from junk. Rob i'm with you on that👍👍👍👍👍👍😉😉 atb Kev

[@Xynudu]

Absolutely Kev. Save the planet.

[@DavoShed]

Good to see you are still hard at it Rob 🤠

[@Xynudu]

Yes. There's usually something on the go Davo. These one off projects are a good learning curve and time waster. Cheers Rob

[@DavoShed]

@@Xynudu Your not wasting time mate :) I never thought of those things having a rectifier inside. Makes sense when you think about it. Has to go from ac to dc somehow 🤠

[@Xynudu]

Yes. It was so bloody obvious, but never crossed my mind until now. Strange how the old mind works. Certainly a handy item to salvage, even if it's just for the diodes. They are not all DC, quite a few are AC, so just bust open the good ones :)

[@SteamEngines-Jim]

This is just cool to watch stuff like this, electronics is above my paygrade.....lucky I have a mate in town Rob that I can lean on. They need to do another run of these Tarot engines, I don't think they are available at the moment as a few people have asked me where I got mine - Cheers Jim

[@Xynudu]

Hi Jim. Lots to learn with electronics. I have very limited knowledge on this, but am slowly picking up useful aspects. I see the two places that sell the Tarot beam engine are both sold out. I expect they will get more in as the web pages are still up. It's an excellent engine for this sort of stuff. Cheers Rob.

[@BigglesFlysAgain]

Maybe put a capacitor across the dc output to reduce the pulsing.

[@Xynudu]

I did that in a follow up video and it also raised the DC voltage.

[@SeanBZA]

Do ont throw transformer away, has $10 of copper wire in it, and it is easy to strip those laminations off.

[@tek4]

Boom. Hi. Cool.