Test Equipment Anonymous (TEA) : Discussion and Group Therapy Thread

[tggzzz]

Unfortunately in times past too many junior engineers were given the boring task of providing a power supply for the interesting bits.

I wonder why the power supply had the reputation of being a principal failure point?

[mnementh]

Batten down the hatches.

Welp… that’s enough of that…

mnem
*fucks off back inside where there’s hot fresh home-made waffles and bacony eggs*

[mnementh]

This storm is projected to be much worse than the last one; supposedly 13-20"/33-50cm over the next 2 days, and they're warning that with expected freezing rain power outages could last 3-8 days. This is the first we've seen where the severe weather warning was more than the default 1-3 days you always get from NOAA.

Seeing that, yesterday I bought a bigger generator; one with 240V that'll actually run the heat as well as fridge & lights, etc.

Freaky part is I went to my local Horror Fraught (same company I bought my little 1KW unit from over a decade ago) and they had a 20% off coupon... (when does that ever happen when you need one!) which $100 off just aboot offset the special plug and 2 cans full of gas I bought afterwards.

Got back just in time to see the fluffy stuff coming down... hope we don't need any of it, but still not even imagining taking it back and paying the 20% restocking fee.

mnem
I have the powaaahhh!

[mnementh]

. .



a few pics from the last storm... I thought I had already posted these...

mnem
hold onto your butts!

[MED6753]

So far the "blizzard" here has been a non event. Yes, we have significant snow and some blowing but so far it's much less than the storm a month ago. Easily managed and dealt with. But not so in NYC, Long Island, and where Paul and Pat are located in Connecticut. I'm about 50 miles from the coast and the storm is more slightly off shore so they are getting hammered but not here. The storm is expected to continue thru today (Monday) with totals over 2 feet in some areas. I really doubt we'll get that here.

[mnementh]

Well, I foolishly bought another treasure on fleabay, without realising how big it is. I've decided to use it as scenery for a futuristic (no steam engines!) OO/HO train layout, representing some form of electrical grid installation.

Any comments?
Some of the above is true

Ummm... tzzzzzzzzzzzzzzzt...?

mnem

[mnementh]

So far the "blizzard" here has been a non event. Yes, we have significant snow and some blowing but so far it's much less than the storm a month ago. Easily managed and dealt with. But not so in NYC, Long Island, and where Paul and Pat are located in Connecticut. I'm about 50 miles from the coast and the storm is more slightly off shore so they are getting hammered but not here. The storm is expected to continue thru today (Monday) with totals over 2 feet in some areas. I really doubt we'll get that here.

Up here, supposedly the worst is yet to come; blizzard conditions thru Tuesday. And freezing rain is definitely a "big scary"; our infra is all pole-to-pole around here.

mnem
*hiding out in Mark Twain's back yard*

[tggzzz]

Seeing that, yesterday I bought a bigger generator; one with 240V that'll actually run the heat as well as fridge & lights, etc.

Surely you can just use the old skool technique: putting the fridge (and probably freezer) contents outside

Or prepare for next time and use the ancient technique: build an "Ice House" a.k.a. Ice Wells, Snow Pits. http://www.historyofrefrigeration.com/r ... ce-houses/

"This scientific project also enabled Charles to entertain and impress by providing chilled drinks and ices to his retinue and guests, even in the height of summer."
https://www.countrylife.co.uk/comment-o ... ered-20789


Plenty more: https://britishlistedbuildings.co.uk/10 ... ville-ward

[tggzzz]

Or other techniques...

Make your own freezer packs with 120g/l salt in water, in 75% full plastic bottles. That should work for a few days, but not a week.

To verify they worked and the temperature never rose, freeze some ice cubes and put them in a plastic bag. If the temperature becomes dangerously high, they stop being cubes

[tggzzz]

Back to our raison d'être...

I've recently tested a PSU set to 40mA 30V, with a 47ohm resistor so it should limit at ~2V. It output 30V for >100ms, then exponentially fell and undershot, and after a second got to the correct value!

Here are some results for PSUs available to me.

The good:

• AIM-TTI PL303QMD-P
• Rapid PS3025 / Manson EP-613
• Tenma T2-10505 / Korad KA3003D
• Power Designs 2020

The bad:

• Farnell PDD3502A

The ugly:

• Maplin N93CX / Manson NRP2050
• Eventek KPS305DF

I've added measurements of the output capacitances.

Most are 100-400uF, but the dismal Eventek is 2800uF. That is in the right ballpark for the over-voltage decay time constant (~150ms) with 47ohms.

[mnementh]

Pics from digging ourselves out yesterday after the 2nd "Storm of the Century" in the last month... we got lucky, as they were talking 13-20"/30-50cm and freezing rain with possible week-long power outages. (Our infra around here is all still pole-to-pole). Not regretting spending on the larger generator; rather have it and not need it than vice-versa.

mnem
I feel... juicy.

[mnementh]

Jeebus... just dug ourselves out, and now blizzard conditions again starting right in the middle of the morning commute. Fuck, but mother nature is being a cunt this winter.

mnem
ehhh… she probably saw Rump's State of the Onion Address last night…

[Cubdriver]

IMG_6754.png

[tggzzz]

IMG_6754.png

I have one like that at the moment. Can't correlate a tinkling (for want of a better word) with anything except >50mph.

Current hope is fan/etc in ventilation system.

Will have to get daughter to attempt to localise noise when she's here in a week's time.

[Zenith]

Back to our raison d'être...

I've recently tested a PSU set to 40mA 30V, with a 47ohm resistor so it should limit at ~2V. It output 30V for >100ms, then exponentially fell and undershot, and after a second got to the correct value!

Here are some results for PSUs available to me.

The good:

• AIM-TTI PL303QMD-P
• Rapid PS3025 / Manson EP-613
• Tenma T2-10505 / Korad KA3003D
• Power Designs 2020

The bad:

• Farnell PDD3502A

The ugly:

• Maplin N93CX / Manson NRP2050
• Eventek KPS305DF

I've never liked the idea of switch mode bench power supplies, although I'm sure if you pay enough for them they are excellent.

I've had a Manson EP-613 for years and found it fine. Mine's branded Altai. They had all sorts of brands put on them, Rapid etc.

The one I use the most now I'd guess is another generic one, but this is branded Velleman. It has a few irritating things, such as no fine control for the voltage. I suppose I could modify it to include that, but I've gotten used to the safecracker fingers approach.

I feel obliged to test them with a DSO now.

[tggzzz]

[I've never liked the idea of switch mode bench power supplies, although I'm sure if you pay enough for them they are excellent.
...
I feel obliged to test them with a DSO now.

I'm not sure that either price or manufacturer is sufficient to guarantee behaviour in this respect

Testing is fun, but the tests ought to bear a resemblance to how the PSU will be used. I note those tests are with a low current limit, 40mA, and that it isn't easy to set some of those PSUs to that value.