VCO temperature stability testing chamber

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EATyourGUITAR
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VCO temperature stability testing chamber

Post by EATyourGUITAR » Tue Mar 17, 2020 3:55 pm

I read over on the EEVBLOG forum that someone was using this to do temperature stability testing. you can hack it to have the raspberry pi do the PID and the data logging for fully automated testing. this has been on my mind for a while but now it looks a bit easier to build now that I see someone doing it.

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Re: VCO temperature stability testing chamber

Post by jorg » Tue Mar 17, 2020 4:38 pm

EATyourGUITAR wrote:
Tue Mar 17, 2020 3:55 pm
I read over on the EEVBLOG forum that someone was using this to do temperature stability testing. you can hack it to have the raspberry pi do the PID and the data logging for fully automated testing. this has been on my mind for a while but now it looks a bit easier to build now that I see someone doing it.
That's brilliant and cheap! I imagine many folks here would use it just as is (no automation needed, e.g. for calibrating a VCO).
TempChamber.PNG
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Re: VCO temperature stability testing chamber

Post by jorg » Tue Mar 17, 2020 4:40 pm

Somehow quoted myself - oops.

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Re: VCO temperature stability testing chamber

Post by EATyourGUITAR » Tue Mar 17, 2020 4:43 pm

true. I was thinking more like a manufacturer. you need a lot of data. you need to data logging of conformity while you sweep the temperature range at different speeds. you need to test quick changes in temperature. I would rather do it in my sleep. do you record temperature, voltage, Hz manually? semi-automated? what does your current test setup look like?
Last edited by EATyourGUITAR on Tue Mar 17, 2020 4:44 pm, edited 1 time in total.
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Re: VCO temperature stability testing chamber

Post by EATyourGUITAR » Tue Mar 17, 2020 4:44 pm

double
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Re: VCO temperature stability testing chamber

Post by Synthiq » Tue Mar 17, 2020 5:39 pm

Interesting, but unlike real temperature chambers it lacks a port to bring in cables to it so the question is how to power the vco and bring out a signal.

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Re: VCO temperature stability testing chamber

Post by xaothewretched » Tue Mar 17, 2020 6:49 pm

Looks like fun. Post pictures.
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Re: VCO temperature stability testing chamber

Post by EATyourGUITAR » Tue Mar 17, 2020 10:17 pm

Synthiq wrote:
Tue Mar 17, 2020 5:39 pm
Interesting, but unlike real temperature chambers it lacks a port to bring in cables to it so the question is how to power the vco and bring out a signal.
I was thinking about this. two options. run the wires through the gasket in the door. or you cut some holes in things. don't drill through anything important. don't drill through live mains while plugged in. I say this now because I have no idea who is reading this.
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Re: VCO temperature stability testing chamber

Post by Flounderguts » Tue Mar 17, 2020 11:14 pm

Or just drill through that useless piece of clear plastic (it can't be glass, can it?) in the door. I'd recommend cable glands, since hot glue might melt when you're heating it. Or silicon, I guess :hmm:

Chances are it pops apart pretty easily...you could put some banana jacks in the floor...
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Re: VCO temperature stability testing chamber

Post by KSS » Wed Mar 18, 2020 12:55 pm

No link or pic in OP?
pic in first response is what's being discussed?
Price? Link please?

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Re: VCO temperature stability testing chamber

Post by EATyourGUITAR » Wed Mar 18, 2020 12:58 pm

turn off no script. the link is working. must be on your end.
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Re: VCO temperature stability testing chamber

Post by KSS » Wed Mar 18, 2020 1:22 pm

EATyourGUITAR wrote:
Wed Mar 18, 2020 12:58 pm
turn off no script. the link is working. must be on your end.
Where would I do that? No MW account settings available, and no link shows in your OP. Maybe give me a search term to use? Already tried 'eevblog temperature stability testing chamber'

URLs in other posts on MW are working for me

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Re: VCO temperature stability testing chamber

Post by EATyourGUITAR » Wed Mar 18, 2020 1:39 pm

if I type a link to a product on amazon, PHP BB will grab it and edit the link to turn it into an iframe HTML tag. I have no control over that. the forum is censoring the links I am trying to share. this is fine most of the time but it is not compatible with all devices and browsers. either the mods can fix it or I need to hide the links in a url shortener like bitly. here is the offending code that I got from ctrl+U (view source) in firefox.

Code: Select all

<span data-s9e-mediaembed="amazon" style="display:inline-block;width:100%;max-width:120px"><span style="display:block;overflow:hidden;position:relative;padding-bottom:200%"><iframe allowfullscreen="" scrolling="no" style="background:url(https://www.amazon.com/favicon.ico) center no-repeat;border:0;height:100%;left:0;position:absolute;width:100%" src="//ws-na.assoc-amazon.com/widgets/cm?l=as1&amp;f=ifr&amp;o=1&amp;t=&amp;asins=B07VF42J9S"></iframe></span></span>
and here is the link I guess

h t t p s : / / w w w . a m a z o n . c o m / d p / B 0 7 V F 4 2 J 9 S /
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Re: VCO temperature stability testing chamber

Post by KSS » Wed Mar 18, 2020 1:47 pm

Code: Select all

http://www.amazon.com/dp/B07VF42J9S/
Thank you EYG.

FWIW, I put it without the code tags and it disappeared in my post. Same as what I'm seeing in your OP. Adding code tags gives present result.

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Re: VCO temperature stability testing chamber

Post by Rigo » Wed Mar 18, 2020 2:10 pm

3 times the url ...

Code: Select all

[url]https://www.amazon.com/dp/B07VF42J9S[/url]
https://www.amazon.com/dp/B07VF42J9S

Code: Select all

[url=https://www.amazon.com/dp/B07VF42J9S]click here[/url]
click here

Code: Select all

https://www.amazon.com/dp/B07VF42J9S


... so the last one is missing

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Re: VCO temperature stability testing chamber

Post by Be Sandy? » Wed Mar 18, 2020 2:36 pm

It appears this is some built in feature of the new software that I haven't found a way to turn off yet. I think turning off urls completely would stop things like youtube etc auto-embedding and mean no clickable links which would be a pain.
The way round it is to remove the https:// from the start of the amazon url.

The full url gives us


Minus https:// we get:
www.amazon.co.uk/gp/product/B000MR8SN2? ... 616030b420

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Re: VCO temperature stability testing chamber

Post by neil.johnson » Fri Mar 20, 2020 4:02 pm

I use an incubator I picked up from eBay, and an HP 34970A data logger. It's quite close to what I use at work.

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Re: VCO temperature stability testing chamber

Post by devinw1 » Mon Mar 23, 2020 10:19 am

Regarding the cable pass-thru; We have some big bucks thermal/humidity test chambers at my day job and the cable pass through is simply just a hole. Then you have a soft foam-rubber cork that is split down the middle partially. Put the cables in and jam the cork in. Simple as can be and works great! :tu:

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Re: VCO temperature stability testing chamber

Post by Flounderguts » Wed Mar 25, 2020 7:18 pm

devinw1 wrote:
Mon Mar 23, 2020 10:19 am
Regarding the cable pass-thru; We have some big bucks thermal/humidity test chambers at my day job and the cable pass through is simply just a hole. Then you have a soft foam-rubber cork that is split down the middle partially. Put the cables in and jam the cork in. Simple as can be and works great! :tu:
I wish you'd just said "put a cork in it!"
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Re: VCO temperature stability testing chamber

Post by devinw1 » Thu Mar 26, 2020 10:47 am

Flounderguts wrote:
Wed Mar 25, 2020 7:18 pm
devinw1 wrote:
Mon Mar 23, 2020 10:19 am
Regarding the cable pass-thru; We have some big bucks thermal/humidity test chambers at my day job and the cable pass through is simply just a hole. Then you have a soft foam-rubber cork that is split down the middle partially. Put the cables in and jam the cork in. Simple as can be and works great! :tu:
I wish you'd just said "put a cork in it!"
:hihi: :hihi:

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Re: VCO temperature stability testing chamber

Post by EATyourGUITAR » Fri Mar 27, 2020 11:12 am

freeze your VCO to -47C instantly with this. the best part is that you can target one specific component on the PCB or you can spray it all over.
https://miller-stephenson.com/product/m ... eze-ultra/
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Re: VCO temperature stability testing chamber

Post by ricko » Mon Mar 30, 2020 11:53 pm

This is probably off topic. The thing I wonder about, with temperature drift measurements, is whether we measure the right thing. (Or, rather, whether other measurements might also be useful.)

The typical measurements seem to be to measure either drift of the response curve at a certain air temperature (ie "warm up" drift) or to compare between the curves at various temperatures after the component has warmed up to a stable state.

However, the current flowing through an exponential convert is exponential to the CV (isnt it?) and the amount of heat generated also depends on the amount of time (how many joules for how many seconds). So, for example, a single-frequency VCO drift test using the lowest input CV only will barely produce any heat, while a VCO drift test using high input CV will produce more. Similarly, a drift test using a chirp or fast sweep where there is barely any time at the heat-making higher CVs will also fail to show heating effects. It seems these factors make it difficult to actually compare drift measurements.

If my memory serves me, it takes less than a second for heat from a transistor to transfer into the plastic case (like a DIP), but 5 seconds for it to reach the outside of the plastic case and start radiating out. And similarly, if you are using an on-off heater design in the VCO there is thermal inertia too fir the heat to pass (through the substrate?) So I wonder about the temperature effects on pitch during the playing of notes: that kind of 0 to 10 second interval. How can we measure that kind of change? I wonder if the best approach is to do something like have the oscillator with all settings at the middle panel settings, cold start then 5 minutes at 0 volts input, then apply CV to get 10 seconds each of 50 Hz and 500 Hz for 5 minutes, do it at say 20 degrees C (68F) and 30 degrees C (86F). Testing response at standardized frequencies tells you the musical impact, IYKWIM.

I think that would give a wider range of information about how a module acts in closer to real (not extreme) conditions. And it test the module in use, not just the design. And it would allow better comparisons of any note- and phrase-time drift. If we had a VCO with zero drift on any one note held for 10 minutes, but it could be 50 cents out for the first 5 seconds of far-apart notes, would we regard it as wonderful? (Would we notice? :-) )

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Re: VCO temperature stability testing chamber

Post by KSS » Tue Mar 31, 2020 12:38 am

The question is whether it matters as much as all that.
Vintage analog synths have been using the simple method with 3% tempco parts -which are often much worse in 3350 PTC adherance than the 3% implies.
And yet we have generations of 'wonderful' music from them.

You can find on this site and others a few poste like yours seeking ways to improve the accuracy over temperature variations. It's not a bad goal. But it might be a how many angels can dance on the head of a pin kind of thing.

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Re: VCO temperature stability testing chamber

Post by ricko » Tue Mar 31, 2020 9:25 am

Hmmm: people make wonderful music with two sticks too. It is no reason not to try to understand things. Measurements allow engineers to pick appropriate designs: it is not a musical decision, it is pre-musical engineering information. And we dont seem to have this information.

An engineer/designer might decide that it is fine if, for the VCO they are designing, the exact initial tuning of every note depends on the notes just before it (which also describes portamento.) But if they decide otherwise (or want to make it a user decision) I am interested in what tests could allow comparison of alternatives.

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Re: VCO temperature stability testing chamber

Post by devinw1 » Tue Mar 31, 2020 10:08 am

double post
Last edited by devinw1 on Tue Mar 31, 2020 10:10 am, edited 1 time in total.

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