[sdiy] Caps, nerds, New Year's Eve and soakage

Rick Jansen rick.jansen at xs4all.nl
Wed Jan 3 20:43:02 CET 2018


Wow, a novel way to generate electricity!

Reminds me of those Atmos clocks, that are “eternally” powered by a helium filled can that expands and contracts with the day temperature. 

r.

> On 3 Jan 2018, at 20:01, Richie Burnett <rburnett at richieburnett.co.uk> wrote:
> 
> Interesting experiments Roman! ...but you bottled out only charging that 400v cap to just 32 volts! :-)
> 
> How constant do you think the temperature was during your experiment?...
> 
> I wonder if the voltage changes you measured could be attributed to a change of capacitance with ambient temperature. It is charge that is conserved, so terminal voltage would rise and fall slightly with temperature unless the capacitor has zero temp coefficient. 
> 
> -Richie,
> 
> Sent from my Xperia SP on O2
> 
> ---- SHELLY wrote ----
> 
> Roman —
> 
> I have also found unexpected soakage in polypropylene.
> 
> http://ijfritz.byethost4.com/super_sh_rand_web.pdf
> 
> Ian
> 
> 
> Sent from XFINITY Connect Mobile App
> 
> 
> ------ Original Message ------
> 
> From: Roman Sowa
> To: synth-diy at synth-diy.org
> Sent: January 3, 2018 at 8:15 AM
> Subject: [sdiy] Caps, nerds, New Year's Eve and soakage
> 
> As a last activity in the office the last day of 2017 (Friday 29th) I 
> have charged a bulky polypropylene capacitor up to 32.1V with the 
> intention to measure it after going back on first Monday of 2018 (here's 
> the New Year's Eve part of the subject).
> The cap is 1.5uF/400V from year 1987.
> To my surprise, after almost 4 days, or more precisely 88 hours, it was 
> still charged to more or less the same voltage. Unfortunately my meter's 
> input resistance is 10Mohm for ranges above 10V, so it started quickly 
> discharging during measurements. First reading was not too big as it 
> started in the middle of converter cycle, and next one was 31.2329V with 
> the next ones dropping by about 0.5V each. So assuming the meter was 
> connected about 1.5 cycle earlier, that indicates it was really about 
> 32V at the start. No drop whatsoever during 88 hours!
> To make more precise measurements, I then charged it to 10V, in order to 
> take advantage 1Gohm loading of the meter, and left it for another 29 hours.
> Yesterday's reading - 10.0004V
> Today's reading - 10.0277V
> Not only it did not drop, but voltage rised by 27mV! I think that's 
> dielectric absorption. After all, it was charged to 32V for 4 days, so 
> it could have soaked a bit. OTOH I wasn't expecting any absorption 
> effect to be aparent in polypropylene capacitor.
> So now I discharged it and let it rest till tomorrow to see how high it 
> can go by itself.
> 
> Roman
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