Recent Posts

1

Projects, Designs, and Technical Stuff / Re: How to make a one-transistor bjt 2KHz amplifer work over 3.3 to 4.2 V Vout=1-V

« Last post by magic on Today at 09:52:19 am »

Your circuit already consumes more than 25μA, because you have a few μA in the base voltage divider

Isn't it good enough as it is? Tweak it to get 1.5V across Rc and 0.15V across Re at 3.3V supply. Seems good enough?

If supply increases by 0.9V, base (and emitter) voltage increases 0.1V, collector voltage decreases 1V (but also increases 0.9V). Seems good enough?

2

Power/Renewable Energy/EV's / Re: Smart Meter Installed

« Last post by IanJ on Today at 09:49:05 am »

All,

In my system I am reading import and export power, but not from my EDMI Smart Meter, I fitted my own Owen Brothers modbus capable OB418 meter.
As I have stated before I also notice a residual import wattage when solar is making more than enough to power the house.......it varies between 1W and 20W, sometimes it is 0W.

Here's the spec, which may offer some insight as the EDMI Smart Meters are probably something similar:

From the OB418 manual:
-lref = 10A
-ltr = 1A
-lmax = 100A
-lmin = 0.5A
-lst = 40mA

Not from the manual, I believe this is the terms:
Iref (Reference current) = 10A: This is the reference current used for calibration. It’s typically the current at which the meter operates with its highest accuracy.

Itr (Transition current) = 1A: This is the current at which the meter transitions from low-current measurement mode to normal current mode. It’s a threshold below which the meter might use a different mechanism or mode for accurate measurement.

Imax (Maximum current) = 100A: This is the maximum current that the meter can safely handle and measure without damage or loss of accuracy.

Imin (Minimum current) = 0.5A: This is the minimum current that the meter can reliably measure. Below this current, the meter may not give accurate readings.

Ist (Starting current) = 40mA: This is the starting current, which is the lowest current the meter can detect and start measuring.

Ian.

3

Beginners / Re: Lifting and tilting 0402 SMD LEDs by solder paste while soldering

« Last post by kanaron on Today at 09:45:03 am »

Im using stencil from jlcpcb. 100um

4

Repair / Re: screws, bolts and fasteners used on vintage TE

« Last post by tatel on Today at 09:39:35 am »

After looking at the vernier of mi caliper through a printer loupe, I would say diameter is 3.46 mm +/- 0,02 mm

From https://en.wikipedia.org/wiki/British_Association_screw_threads 4BA has 3.60 mm outside diameter. 6/32 and 6/40 both have 3.5052 mm outside diameter and I'm unable to find anything closer to 3.46 mm so I'm going to try 6/32 set screws.

This AliExpress seller seems to be one of the cheapest and one can choose between 304 stainless and 12.9 steel. https://www.aliexpress.com/item/1005007168325606.html

Another Ali seller: https://www.aliexpress.com/item/1005006097897350.html

And one from Ebay: : https://www.ebay.com/itm/185383761203

Not really sure if 304 stainless would be better than 12.9 steel.  I guess, to avoid rounding the hex socket heads, on these little set screws, one should choose a good steel alloy. 12.9 sounds like plenty. When I was into speleology, we used metric 8 machine screws made from 8.8 steel to hold the ropes in pits. Would be 304 stainless tougher than 12.9 steel? Or would it be better because it wouldn't rust?  What would you choose?

I'm attaching a pdf with some pomona screws that at first glance looked as if they could be used on some Fluke devices to fasten covers, etc, but after a close-up look, that seems to be wrong.

If after some repair you happen to know what screws could be used in any vintage device, could you please report about it?

5

Test Equipment / Re: Rigol DHO914S high temperature / overheating probe inputs

« Last post by Elextro on Today at 09:38:18 am »

My oscilloscope, which is a DHO 802, also get a little hot at the BNC inputs and at the rear AWG output. It is not a very high temperature, but I confirm that it does heat up. I think that the front inputs get hot because they are screwed to the frontal metal chassis which acts as a heatsink and shielding at time. Greetings

6

Test Equipment / Re: Magnova oscilloscope

« Last post by Sorama on Today at 09:36:16 am »

The statistics function is also a great addition. While the numerical values are the most useful, seeing the variation on a graph is a real bonus. As for the math functions, they cover a wide range of logical and mathematical operators. However, some functions are still missing, such as the absolute value, for instance.

As Woody has already mentioned above, a software update is available. Among other things, the function you requested for the maths channels (absolute value) has also been added.

How to perform the update:

• Download the update from the following link: http://batronix.com/magnova/dist/stable/latest.updt
• Copy the downloaded file to a USB stick and initiate the update via the Magnova update dialog (Menu "Settings" -> "Update").

Alternatively, you can update the Magnova directly over the internet:

• Ensure your Magnova is connected to the network.
• In the update dialog, select the "Network" option to perform the update automatically via the internet.

We will create an web page with the update details, version and change information in the coming weeks. Currently, we are manually informing customers who have already received a Magnova.

tnx.

Btw, we ordered a BMO200 this morning :-)

7

Other Equipment & Products / Re: Brother (possibly also some Bernina) embroidery machine memory cards

« Last post by MarkMLl on Today at 09:34:15 am »

I've updated my PES-reader program at https://github.com/MarkMLl/pesdump after another user checked it and highlighted some compiler-version problems (my fault: I'd reverted to an old compiler and made some changes, then hadn't tested it with the most recent).

Discussion at https://github.com/MarkMLl/pesdump/pull/2 has this

I've tried to get some free PES sample files to play around. Interestingly, Brother themselves provide some here: https://sewingcraft.brother.eu/en/inspiration-and-events/projects-and-free-patterns

Even more interesting: the newer files from 2024 seem to use newer file versions (seen 0080 in the "Paw Print" and even 0100 in the "Easter bunny"). So this file format still needs to be extended with new features - I am surprised! Going further down the list, the "Magic mushrooms" (file name Embroidery202401pes.pes) is the first one that uses an older version (0001) and that worked with your tool.

I've not yes attempted to follow the new file format up. If anybody finds themselves needing it then please speak up.

MarkMLl

8

Buy/Sell/Wanted / Re: Lots of test equipment for sale on UK auction

« Last post by tggzzz on Today at 09:32:47 am »

PPAuctions has very variable quality items. Some are fine, some are only worth instant disassembly into component parts. (One such item yeilded only a decent OCXO and a piece of metalwork that enabled me to have a Christmas dinner; long story, not repeating it!)

It is located at a farm, and storage can be a barn. Look carefully at the pictures to see which items are in the barn.

I notice that they are now marking some items "spares or repairs". I haven't seen that before, and I'm not sure what to think about items not marked that way.

9

Projects, Designs, and Technical Stuff / Re: Recommendation Request - Neg to Pos regulator

« Last post by Zero999 on Today at 09:29:54 am »

Obviously trying to keep parts count and price low.  Any recommendations?

-24 to +5 is a sitter for a simple flyback converter. You just need to level shift the feedback.
A PNP matched pair transistor gives tempco matching, and 4 or 5 resistors will shift the +5V feedback to a typical 1.25V reference above the -24V

Something like this? I haven't simulated the switched mode, just the concept.

There are errors due to Q1's base current and the Early effect. Adding base resistor equal to R1 to Q2 will compensate for Q1's base current and cascoding Q1 with a small P-MOSFET will reduce the Early effect.

 voltage mirror.asc (1.72 kB - downloaded 1 times.)

I'd be tempted to use an op-amp and P-FET. The only downside is P channel JFETs aren't so common nowadays. It will also work with a MOSFET, but then there are the issues with the much higher gate capacitance and protection against exceeding the maximum V_GS rating. The J-FET solution also has the advantage of the op-amp been able to be run off 5V.

 voltage mirror op-amp.asc (1.22 kB - downloaded 1 times.)

10

Test Equipment / Re: Rigol MSO5074 Logic Analyzer issues

« Last post by tggzzz on Today at 09:25:02 am »

While using a USB streaming LA is a viable alternative for this scenario, once you understand the scope it should do what you desire. Using a scope for this kind of work is a different workflow to using an LA: with a scope it's all about the triggers, whereas with a USB streaming LA it's a data grab and post processing. There are pros and cons to both, and it's not really a one-size-fits-all. I use both on a daily basis, but typically I go for the MSO first as I've been brought up with scopes and triggers. YMMV, I can see the friction of a learning curve around the scope might well be a turn off.

With a decent LA it is all about triggers and filters.

The filters allow you to ignore irrelevant time-domain noise, and concentrate on digital domain signals.

Simplest example: only capture data at a clock transition, since anything between clock transitions is irrelevant.
Next example: ignore any of that data that isn't to/from a specified device.
And continue adding filters so you can concentrate on the useful information.

Protocol analysers do the same, but with messages not bits.