Recent Posts

1

Projects, Designs, and Technical Stuff / Re: (Yet Another) DIY Multislope ADC

« Last post by iMo on Today at 06:34:41 am »

..The project files are available, so it should be possible to get your own set of boards for experimentation, or replicate the core circuit (it's quite simple) on a breadboard..

Yep, the analog part of the design is an another story which we have not elaborated yet
My basic motivation has been to have a look at the 2040/PIO and its applicability. Of course it could be done by a stm32xxx (here we lack the PIO) or an fpga+MCU (here the complexity is higher) as well.
Hopefully rPi company will come with the rp2041 soon - with the fixed ADC, and with 4xPIO with 256 instructions each

2

Microcontrollers / Looking for information on TEST pin and ways to DUMP mask ROM of PIC1650 PIC165x

« Last post by reverse on Today at 06:31:41 am »

Hi. Looking for information on TEST pin and ways to DUMP the mask firmware ROM on GI's (General Instruments) PIC1650  (PIC165x) family of microcontrollers.

3

Projects, Designs, and Technical Stuff / Re: Opamps - Die pictures

« Last post by Noopy on Today at 06:29:16 am »

Nice! Thank you very much! 
Would it be ok for you if I put your schematic on my website?

4

Computers / Re: Format a 256GB pendrive with FAT32 using a windows 10 pc

« Last post by magic on Today at 06:27:10 am »

Not sure if it's a GUI on top of command line tools or a GUI and command line tools on top of C/C++ libraries and APIs.

"GUI on top of command line tools" is how Linux Desktop stuff works, when it does

5

Test Equipment / Re: Standardised Way To Test Oscilloscope Screen Update Rate

« Last post by EEVblog on Today at 06:26:10 am »

I am thinking about the purpose of the refresh rate.
Perhaps the screen refresh rate is less important than the ability to display the waveform appropriately – so a waveform with a 'glitch' repeated at different rates could be used to test for this.

Yes, in theory the display refresh/update rate shouldn't matter if the scope is designed to or set up to capture the thing you are interested in. Persistance is one obvious way to do that for example.
But often you are just causally using you Mk1 eyeball probing around, in whcih case you don't want your fast waveform capture rate hindered by a slow display update rate.

6

General Technical Chat / Re: Relay trigger when voltage above 13v

« Last post by dietert1 on Today at 06:24:10 am »

Here is TI's app note on using the TL431 as a comparator:

Using the TL431 for Undervoltage and Overvoltage Detection
https://www.ti.com/lit/an/slva987a/slva987a.pdf
..

I would replace the bipolar transistor of Figure 6 in that app note by a p-channel mosfet in order get rid of the relay. The voltage sense divider causes a small current drain even below threshold.

Regards, Dieter

7

Projects, Designs, and Technical Stuff / Re: Opamps - Die pictures

« Last post by magic on Today at 06:22:15 am »

The circuit is not very complex and the complete schematic would be near but I somehow don´t like MOSFETs... 

Well, CMOS is annoying, but 30 year old CMOS is doable.

Turns out the signal path circuitry is quite simple, a few differential pairs and current mirrors are all there is to it. Looks like a TLC274 chopped into pieces and reassembled semi-randomly. The trick is auto-zero witchcraft and high DC gain achieved by a sequence of four stages with unusual compensation by two Miller caps and two input pairs. BTW, similar compensation is shown in datasheets of modern three stage CMOS opamps from TI like OPA172 or OPA1656; they call it "active feedforward" and I have also seen it called a "multipath" elsewhere.

The critical pairs gm1 and gm6 use striped common centroid layout ABBAABBA and their mirrors are ABBA. The offset compensation pairs gm3 and gm4 are oriented perpendicularly to output stage heat gradient but don't bother with common centroid. The other small stage gm2 is single-ended and the output stage is a simple rail to rail contraption: M56 sinks load current directly, M51 steals current away from current mirrors driving M55. This arrangement ensures that M56 never turns off, so compensation keeps working when the output sources current.

M58 is a dummy transistor in parallel with C1 which appears to compensate for capacitance added to C2 by M56. It isn't exactly identical to M56, but they must have made it work somehow.

8

Test Equipment / Re: Standardised Way To Test Oscilloscope Screen Update Rate

« Last post by boggis the cat on Today at 06:20:02 am »

I am thinking about the purpose of the refresh rate.

Perhaps the screen refresh rate is less important than the ability to display the waveform appropriately – so a waveform with a 'glitch' repeated at different rates could be used to test for this.

Would setting an AWG to generate a glitch at different rates be a way to verify that the 'scope is functional?

9

RF, Microwave, Ham Radio / Re: Transistor tester

« Last post by max-bit on Today at 06:18:23 am »

But I am surprised that so far no one has developed a "cheap" tester of TRANSISTORS, diodes, thyristors, thraics, with capabilities slightly beyond the "battery" values, so that Uce ~ 100V Ic ~ 1A etc.
It is even very difficult to find (if there are any) such devices from larger companies (but not costing xx k$)

Something in the range of a few hundred dollars to ~$1000

These "toys" have been on the market for many years for prices ranging from several dollars - a dozen or so dollars.

10

Manufacturing & Assembly / Re: Brief review of the Zhengbang ZB2520HL reflow oven (T-962A alternative)

« Last post by niebieski201 on Today at 06:16:17 am »

Hi.
I just collect my RF-A350 oven, I did not try any PCBs yet but when I checked build in reflow profile without any modifications and with thermocouples stick to bottom plate it doesn't look good.
Temperature in the middle is follow the profile but overshoot 5-6 deg. Temperatures 10 cm from middle, each side, seems to also follow profile but are under the line sometimes 10-15 deg, but within few extra seconds they starts following middle temperature.
Can someone share settings or other tweaks for this oven as factory one seems to be not perfect.

Attached factory profile 4 with empty tray.
Regards