Recent Posts

1

General Technical Chat / Re: Why suffer a Farington ? (Maybe because I'm a Farington, also)

« Last post by themadhippy on Today at 01:53:36 pm »

The popularity of Gaynor as a girl's name has really dropped during my lifetime. I can't imagine why

No need to be afraid,  she will survive

2

Repair / Re: Help Identifying Vintage Component

« Last post by Drjaymz on Today at 01:50:20 pm »

Future me here - I've been flying this thing for another year or so and occasionally the Over Voltage relay kicked in and no problem I just turned off the ALT switch, turn it back on again and all is well for the rest of the flight.

When using the landing light at take off (thats 100W) and selecting flaps in, when the flaps hit the stop (there is no limit switch) it crow-bars the 12V bus due to the heavy load.  This causes the charging system to work harder and the voltage occasioanlly overshoots resulting in the Over Voltage relay tripping in.  Except now, it will NOT reset until the engine is shut down.  So this means that current is still flowing through the over voltage relay thereby latching the SCR.

I have supplied the entire charging circuit including the over voltage module we reverse engineered last year.
At the time I realised I cannot reset the alternator I had to land but something else is now.  In the cockpit the ALT warning light has now decided to work after all these years.  It comes on when the ALT switch is turned off.  Now I never saw this light before, it did used to work.

Looking at the diagram the ALT warning light has one side connected to the 12V bus and the other connected to regulator.  That means current is flowing from the main bus to ground via the warning light - and if the OVR is tripped then it has to be via the regulator or via the OVR.

I have checked and this is the way its been wired for 50 years but doesn't make a lot of sense to me.  The warning light looks like it may prevent the OVR being reset by providing some current to the SCR resetting.  Secondly how does the warning light work - because if the switch is off, then the other side of the bulb must be seeing a low / 0V.  Input I on the regulator can't pass current to ground because it has a diode (except for the resistor network) - it has to be passing it through the OVR coil.  If thats the case - how you supposed to reset it in flight?

Last time this happened I tried turning the master off and that didn't reset it either.  I think thats because the alternator has its own ground and therefore if even the tinyest current flows through the fild coils, it will produce an output unless the engines stops.  And sure enough when you turn the engine off, it resets.

Now - this is Aviation and therefore this is a terrible design with long thin wires carrying large current, its also 1970s and on top of that its French.

So what is my actual question?  That ALT warning light that has just decided to start working - do you agree with me, that is preventing reset of the over voltage relay?  What is that light supposed to indicate - you'd think it means the alternator fault but its a bit ambiguous, because it could be off and the generator isn't generating.

3

General Technical Chat / Re: Why suffer a Farington ? (Maybe because I'm a Farington, also)

« Last post by AVGresponding on Today at 01:38:12 pm »

Forenames, at least here in the UK, go in fashion cycles to some degree, and also depend on what current actors/pop stars etc are named

4

Test Equipment / Re: Hacking the Rigol DHO800/900 Scope

« Last post by arturmariojr on Today at 01:38:07 pm »

Is not the 914 model that has more options?

814: Parallel, RS232/UART, I2C, SPI
914: Parallel, RS232/UART, I2C, SPI, CAN e LIN

5

RF, Microwave, Ham Radio / Re: Which NanoVNA?

« Last post by tszaboo on Today at 01:37:34 pm »

Lack of a screen is not larger.

I did take a look at the LibreVNA. I would like to have a standalone device. Plus the heating of the device and the subsequent changes in calibration are annoying.
joeqsmith I did watch some of your videos, and I think it was one with capacitors measured and ESR on the screen which convinced me that I'm missing out on features. So I've been watching VNA videos now...

Guessing that was someone else as I pretty much only use them in conjunction with a PC and my software.   I've had people ask me about this one which has a 7" screen and N connectors:

https://www.sysjoint.com/index.php?tpl=product_detail&pid=11&uid=17&id=12&sno=1&list=2&lang=en 

I don't know anything about it but guessing there is a group for it.

It might have been your software (which is something I wish to try). The videos often go on the background, and I split my attention. The SV6301A you linked is 950 EUR (expensive), and as I said, the reviewers say it's a downgrade in terms of firmware/software.

6

Repair / Re: PreSonus Eris E3.5 broke when turned on / teardown pictures

« Last post by shapirus on Today at 01:37:26 pm »

Found this thread due to having a similar issue.  In my case I am certain it is simply the power switch itself, I have been having intermittent issues for a couple months, which I typically would solve by rocking the switch back and forth just slightly to get the monitors to stay on.  I was investigating a bit further and the rocker fell off with the slightest tug.  Going to look into replacing the switch with something more robust.

Haha, I'm joining the club.

In my case, the switch seems to be broken mechanically. It's stuck in the "on" position. I haven't yet taken the speaker apart, so no idea what happened.

I wonder if it's some standard type/size switch, or I'm out of luck if it has to be replaced. The rocker button itself looks quite standard, but the whole assembly I'm not sure.

Have you found anything to replace your switch with yet?

7

Altium Designer / Re: Altium Libraries

« Last post by bostonman on Today at 01:36:46 pm »

My PCB design experience is with (no laughing) PCAD 2006. Years back my old company was upgrading and gave me a full licensed copy. With the exception of periodic glancing over the shoulders of the PCB group whenever I roamed over to the department, I didn't know anything about laying out a PCB.

Once I tinkered with PCAD, I was able to design the schematic symbol, PCB footprint, schematic, and PCB. Ignoring I don't know all the design rules, I successfully made a few PCBs (although I haven't made a PCB in about ten-years).

I've tinkered with Altium here and there, but technically I don't have any experience. Since I've seen most companies I work at use Altium, I've had an interest in trying to understand it better. From what I can tell, the steps are similar to PCAD, except much cooler since it will generate a 3D model of the PCB.

The PLCC socket has a .step file on DigiKey, and I placed it FreeCAD just for fun to view it (I think 3D models are cool), but not certain whether a .step file contains necessary information for pad spacing and stuff associated with making a PCB. I thought the .step file I had was mainly for 3D modeling/printing.

I have a small Altium library collection, don't remember where I got it from. Maybe at some point I was able to access a library at my old job, so I copied several items from the Altium server, but I'm uncertain. I vaguely remember accessing an Altium library and saying: let me get as many as I can so I have them in the future.

In any case, it seems I have basic transistors and stuff, and, for some reason, a boat load of FPGA libraries.

As mentioned above, the steps I know is: create schematic symbol and footprint (followed by creating a schematic, transferring the net list, and then making a PCB). Those are the only two steps I believe for making a component that will be used for all other PCB design steps.

Does the .step file provide all that information and I already have it because I downloaded the PLCC socket .step file?

8

Test Equipment / Re: Siglent SDS800X HD 12 bit DSO's

« Last post by bateau020 on Today at 01:36:20 pm »

Just so to make it clear what happens with the .csv files: when using csv dump instead of image dump when pushing "save", the file name is like "seg{n}.csv" with n is a 5 digit number. The header in the csv file is like:

Code: [Select]

Record Length,Analog:400000
Sample Interval,5.000000E-10
Vertical Units,V,
Vertical Scale,+5.000000E-04
Vertical Offset,+0.000000E+00
Horizontal Units,s
Horizontal Scale,+2.000000E-05
Model,SDS824X HD
Serial Number,**REDACTED**
Software Version,3.8.12.1.1.3.6
Source,CH1
Second,Value
-1.0000000000E-04,+2.187500E-04
-9.9999500000E-05,+2.052083E-04
-9.9999000000E-05,+2.208333E-04
-9.9998500000E-05,+2.739583E-04
.....

This will also come with a "metadata file" called "C1.awg" that I imagine being for feeding into a AWG, with the following content:

Code: [Select]

sample_rate,2000000000.000000
amplitude,1
run_mode,countinuous
wait_trigger_type,zero
burst_count,1
burst_hold_type,Start Value
trigger_mode,button
timer_interval,0.001
trigger_edge,raise
interp_mode,zero_hold
length_strategy,length
increasing_strategy,interpolation
decreasing_strategy,decimation
file_type,SDS

segment_0,seg00001.csv,-0.000001,0.004259,400000,1,-1,next,0,0
segment_1,seg00002.csv,0.000300,0.002048,400000,1,-1,next,0,0


Not aware of these files following an industry wide standard, but it looks like it is a Siglent inter-device standard.

So: no dates or times, other than relative time.
I do think that adding dates in either the csv file or in the "metadata" file would be a nice addition.

9

Beginners / Re: Determining RGBS Sync Levels

« Last post by jzx on Today at 01:35:32 pm »

15.734 Hz is the official line frequency for ntsc, 15.7 must be an abreviation. Some screens have trouble with interlaced (or with non interlaced signals), the standard for ntsc TV is interlaced, but some consoles give non interlaced signal. (I dont know what does SNES).

What is the model of the screen?

10

Microcontrollers / Re: Lightweight Scripting Language for MCUs

« Last post by Picuino on Today at 01:35:32 pm »

https://github.com/totalspectrum/tinyscript

Introduction

This is tinyscript, a scripting language designed for very tiny machines. The initial target is boards using the Parallax Propeller, which has 32KB of RAM, but the code is written in ANSI C so it should work on any platform (e.g. testing is done on x86-64 Linux).

On the propeller, the interpreter code needs about 3K of memory in CMM mode or 5K in LMM. On the x86-64 the interpreter code is 6K. The size of the workspace you give to the interpreter is up to you, although in practice it would not be very useful to use less than 2K of RAM. The processor stack is used as well, so it will need some space.

tinyscript is copyright 2016-2021 Total Spectrum Software Inc. and released under the MIT license. See the COPYING file for details.