Recent Posts

1

Projects, Designs, and Technical Stuff / Re: Looking for transistor-based 32kHz quartz test circuit

« Last post by Benta on Today at 05:26:59 pm »

32 kHz crystals are extremely sensitive to overdriving. Power limit is usually around 1 uW (yes, that's microwatt!).
I suggest you use a 74LVC1GX04, it's made for the job.
The crystal needs a series resistor to limit power, usually 500k...1Mohm.
Two load capacitances are common, 12 pF and 7 pF.

2

General Technical Chat / Re: Morphy Richards Ductless Portable Air Conditioner funded by Kickstarter!

« Last post by tom66 on Today at 05:26:14 pm »

They're less efficient than a mini-split, sure, but "utter crap" they are not.  Both of ours keep our offices cool in the summer.  Yes, we want whole-home AC, but we're not sure if we're going to be in this house long term, so it doesn't make sense to make the investment in that yet. We only use the portable AC units for about a week a year on the hottest months so the energy consumption is negligible.

two hose or singles?

you can work the math out but the 5K btu 140$ window units are about twice as efficient as single hose ac's unless... you're not paying for the rest of the building to be cooled. so say its 85F outside and you're cooling just one office cubicle at 15 cents an hour. 140$ divided by 7.5 cents an hour is a long time.

Unfortunately, window AC is all but unheard of for UK homes as we don't have the lift-up windows that would be required to fit one of those.  We use single hose units - two hose units are a bit more efficient but I don't see many of those for sale.

The daytime electricity price here is about 22p (~$0.29) and the units use less than 1.2kW running combined (~27p/hr).  So if a proper AC install would cost ~£4,000 to get both rooms done and would then use around half the energy, it'd take about 28,000 hours to break even by my maths...  Given they probably get a total of 300 hours of use a year, it wouldn't make sense from a financial point of view.  It'd only make sense to get better cooling and/or cosmetically it looks a lot nicer.

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Test Equipment / Re: Siglent SDS804/814X HD or Rigol HDO914S for Mechatronics student

« Last post by Fungus on Today at 05:25:30 pm »

I have found only comparison threads between SDS804X HD and HDO804 and from which I can see that SDS804X HD is superior but how about compared to HDO914S?

I wouldn't get the HDO900 series, it has no real advantages over the HDO800. If you can get a cheap HDO804 then go for that instead. It can easily be persuaded to think it's a DHO924.

For Mechatronics you could also look around for a deal on a Rigol MSO5074.

4

Test Equipment / Re: Hioki IM3570 LCR & Impedance Analyzer

« Last post by KungFuJosh on Today at 05:24:18 pm »

I submitted the following suggestions to improve the IM3570:

• PNG format instead of BMP for screen captures (PNG is ideal both for image quality, and to be able to share with peers).
• Custom colors for screen and/or screen captures, or at least an option to invert the screen colors on capture.
• Axis markers for analyzer to make reading and sharing info easier (why is test voltage on the same line as the frequency axis?? A lot of screen space is wasted in this regard).
• Screen capture of any screen, instead of just measurement screen (to share settings, etc. Currently need to take photographs of the meter).
• A simple way to get screen captures remotely, either via software app or a built-in web server on the IM3570 (basic functional control, and/or only remote viewing and screen capturing would be fine, though full control would be great if possible). (The LCR Meter Sample Application is not sufficient, but not terrible either.)
• Screensaver option with options for: Off, 10 minutes, 20 minutes, 30 minutes, 60 minutes.

The service manager responded:

Thank you very much for sharing your valuable feedback and suggestions with us.
We truly appreciate the time and effort you have taken to provide us with your thoughts on how we can improve IM3570.
Your insights are extremely helpful, and we will carefully review your suggestions to see how we can implement them to enhance our offering including our HQ in Japan.
We are committed to continuously improving and your feedback plays a crucial role in that process
If you have any additional comments or further suggestions, please do not hesitate to reach out to us.

Once again, thank you for your continued support and trust in our company.

Hopefully, they'll do at least some of them, but the canned response doesn't give me a lot of hope lol. I guess we'll see.

5

Metrology / Ref80 - A competition to ADR1001?

« Last post by branadic on Today at 05:23:24 pm »

"REF80 is a buried zener, internal heater compensated voltage reference. The device is designed with an extremely low temperature drift and long-term drift. REF80 is also a low noise device."

https://device.report/m/158081276c8014e611d4be1e2e7e80c15bf10773f92c56a97763852ea16d52fd.pdf

Has TI really worked on a competition to ADR1001? HP3458A reading in figure 2-3 indicates a zener voltage of 7.577 V.

-branadic-

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Test Equipment / Re: Fluke 931B RMS differential voltmeter

« Last post by tatel on Today at 05:23:06 pm »

Yep. I'll probably do exactly that as last resort. However I hope there's some people here experienced with these devices, that could perhaps know what's going on.

7

General Technical Chat / Re: Submersible missing while visiting Titanic wreck

« Last post by johansen on Today at 05:19:48 pm »

After whistle-blowing happened there were enough people who knew the design was marginal. Somewhere above i already wrote that in mechanical engineering safety margins of 10 or 20% are very unusual, especially if human life is at risk. Safety checks cause delays and cost money. I think that business wasn't viable as it was nonsense from the very start.

Regards, Dieter

They thought they had a safety factor of 2.25 on the hull, which is something they should have been able to achieve given that the demands on a 5" thick hull 66" outside diameter is only 35,600 psi in hoop stress compression. the us navy did a lot of work on this in the 80's and some of their E2 fiberglass hulls had 110K psi compression strength, even though the samples tested were curved sections cut from the hull and compacted in a press.

I can't seem to find reliable data on the viewport. Stockton actually claims he was 8% off the charts and had a safety factor of 4 on the viewport, in the released transcript of Lockridge's interview. But the manufacturer said we'd only certify it for 650 meters. if you take the usual factor of safety of 6 or 7 for viewports.. this is consistent with one expert's testimony that the veiwport would last "a few dives to 4000 meters" (650*7 is 4550)

a factor of safety 4 viewport would have been more like what you see on the subs that have gone down to 36,000 feet.

8

Metrology / Re: Cost and who to adjust PM2525

« Last post by J-R on Today at 05:16:16 pm »

Can you post a link to the complete service manual?

9

Other Equipment & Products / Re: CFW for STM32 OLED Digital Soldering Station with T12 Handle

« Last post by Chris02 on Today at 05:16:06 pm »

Edit: It's similar to the KSGER v2.1 but seems to have some differences?

The display, encoder, PWM seem to be the same as the KSGER v2.1, but there are pins with unclear connections.

I didn't find anything about the CEIAH IC.
Seems  to be an independent voltage regulator for the analog? Or at least it sems to power only the op-amp and the stm32 VDDA.
I don't see the NTC anywhere, it's probaby in the handle like the KSGER. Or it might use the internal stm32 sensor.

I see the earth (PE, R25) is joined to the internal ground with a solder bridge. At least in mine, this causes a big reading offset > 70ºC.
I left the original 100K resistor there.

As a reference, check the v2.1 64 pin schematic.
https://github.com/dreamcat4/t12-t245-controllers-docs/blob/master/controllers/stm32-t12-oled/v2.1s-and-Ve2.1S/KSGER%20STM32%20Ver2_1S%20schematic%20rev%202_floobydust.pdf

Don't compare the pin numbers, but the pin names.
Ex.  PA2 is pin 12 in 48-pin package or pin 16 in 64-pin. If the same signal go to to PA2 in both, the firmware would work right away.

Hello,

is there any schematic how to make t12-955 C245 compatible? I'm sure anyone did it already, but I din't find something.

And I adapted a Quicko T12 soldering station to work with C470 cardriges (JBC Heavy Duty series). If it is interessting I can share it. Just some small HW modifications are necessary.

Regards
Chris

10

Test Equipment / Re: Portable Oscilloscopes List (cheap)

« Last post by Aldo22 on Today at 05:16:01 pm »

I didn't claim that it was better.
I meant that the oscilloscope is roughly equivalent but costs half as much.
If the DMM or the signal generator of the Owon is important to you, then the Owon is better.

Forget the bandwidth, there is no significant difference.