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Projects, Designs, and Technical Stuff / Re: Making an LVDT
« Last post by moffy on Today at 06:58:42 am »
This Linear Technololgy note describes a nice simple LVDT interface:
The 2 ranges for the current setting make some sense, kind of an alternative to a 10 turn pot. One quite often needs current limits well below the full capability of the supply.
There is no real need to overdo it with the resistor accuracy in the set part, as there is anyway the pot to set the values. It would only be the read back part that may want reasonable stable / accurate resistors. For the voltage regulator the offset of the OP-amp should not be that relevant. So a TL071 is OK there. It is mainly the current part that may want low offset / low drift, so that the reading of the set point has not to much offset from the final actual current limit.
Test Equipment / Re: TC1 lcr-meter transistor-tester fix
« Last post by madires on Today at 06:52:50 am »
Sorry, I don't provide compiled firmwares.
I'm sure a lot more concerned by wide misuse of public money on dead-end projects, rather than individuals trying funky (or just plain stupid) stuff and talking about it in videos. They make money from the exposure, sure, but at least they're not taking money from people without their consent. So I don't have much problem with that. And there are enough of us to debunk the stupid stuff.

I agree with Nominal that just getting people interested in those topics and experimenting is a good thing.
Other Equipment & Products / Re: Any opinions on the Aixun T420D?
« Last post by digger on Today at 06:44:51 am »
actually, i got the set with all three handles because it ended up being about a dollar cheaper, lol. by spending slightly more, a better coupon triggered. i guess i'll see how it goes.

still, if anyone knows the answers to my questions, i'd love to hear more.
Are you sure it is set up properly?

No idea :D  Can you configure/tune hysteresis and control loop params in these consumer units?

I've got the user manual and install manual but they don't mention anything about software setup or tuning.  (EDIT: both available online under "Downloads").  The user manual straight up says that you specify the "desired" temperature with the remote, which is what I would expect but don't see.

Heck, are you sure it is actually what you think it is?

Yes, I've checked the model number on the outside unit and Rinnai's site says it's an inverter unit.  Its current draw also varies quite a bit (I've made readings that roughly equate to around 300W and 600W).
Now I can learn something about electronics.

...and book binding, freshly printed editions?  :palm:
Repair / Re: 30v Power supply does not go over 7.9 volts
« Last post by FIXITNOW2003 on Today at 06:28:51 am »
if you search "power supply K305" you will find loads off post on these units, lots off Chinese makers but all the same unit lots off faults mostly poor soldering and duff diodes
My process is as follows:

1) Get the pin alternate names by exporting from STMCube to CSV (or copying off datasheet).
2) Use a concat formula in excel to add in the "/" where required.
3) Setup a new symbol with the correct number of pins you have and select all the pins.
4) Open up the schlist panel and sort by designator.
5) Copy and paste in the concatenated names.
6) Open the symbol wizard and re-place the symbol.
7) Change the display name in the schlist or directly in each pin to the default name, usually it's GPIO or Power pins. This is what will show in the symbol library. If you don't do this your symbol in the library will be a mess.
7) Place the symbol in schematic and turn on/off the relevant functions to suit your design.

Notes: The schlist on its own won't work to paste in the alternate functions hence why you need to do this in two steps. Schlist, then symbol wizard.
This is because the Symbol wizard will not sort nicely. It sorts as 1,10,11,12 rather than 1,2,3 etc which the schlist does.

If you define pin electrical type / description / IEEE symbols etc then those have to be manually updated. I'm ok with that as the value is in the ability to 'see' the alternates if needed and only show the one you are using making the schematic more readable.

Repair / Re: Weird USB oscilloscope ground issue?
« Last post by 2N3055 on Today at 06:23:13 am »
This is not ground loop question. Something is wrong.

240mV voltage drop with 180mA current suggest 1.3 Ω resistance.

I don't often disagree with you but here I'll have to, not on the fact that the resistance is rounded down from 4/3 \$\Omega\$  ;D
There is a ground loop sketch it out, you'll see... Probe ground, USB ground and PC ground are all common now if you connect the probe ground to another length of wire leading to the PC's PSU inlet ground connection you create a loop which is also an additional return path for the supply current to the Picoscope. This alternate return path runs through the Pico's frontend ground tracks and probe ground wire which also have resistance (say approx. 1.3 \$\Omega\$) so measuring anything is offset by the voltage drop across the probe's ground wire.

Edit: OTOH you weren't saying there wasn't a ground loop, rather it wasn't the problem. It still looks the most plausible problem to me considering it's DC.

My English. Sorry.

There is a wire loop. Always is when you measure with any scope.

Problem is that voltage is DC and is huge. That is what I meant.
Ground loop is not source of the problem, it is what allows us to measure that something is injecting current to ground. And it should not. And even if it does, impedance of grounding should be lower.

10-30mV is normal.
250mv means something is wrong.

All the stuff on your desk should be connected to same grounding point.
Connected with short cables, there should be order of magnitude less potential difference in what essentially aspires to be equipotential net.
Something is not right with grounding and/or power distribution wiring.

In addition to DC current being injected into ground from somewhere. Also not right.
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