Recent Posts

1

Beginners / Re: Resistor ????

« Last post by soldar on Today at 05:31:33 pm »

The value wouldn't start with black unless the multiplier band was silver, and 180 would be BROWN grey black black.  The grey/silver band has a sheen to it that differs from the pigment bands so is probably metallic silver rather than grey.   Perhaps this color-balanced zoomed in view of it will help.

Its a tossup between:
   Brown (1) Black (0)  Black(0) Silver (/100) Black () = One ohm, with a mystery black final band (as black isn't a tolerance color)
and:
   Brown (1) Black (0)  Black(x1) Silver (10% Tol.) Black (250ppm TC) = Ten ohms, 10% tolerance 250ppm temperature coefficient.

You are correct, of course. I had a brain fart there. I blame it on the flu I am undergoing.

2

Microcontrollers / Re: How to create custom bootloader in esp8266

« Last post by tooki on Today at 05:29:33 pm »

They said they want OTA (over the air, i.e. WiFi, Bluetooth, etc) updating. So I don’t think they’re referring to the hardcoded bootloader’s ability to load from serial.

3

General Technical Chat / Re: $20,000 dollars of software or licences on a thumbdrive ?

« Last post by strawberry on Today at 05:29:14 pm »

expected 3y lifetime and 1/5000 failure rate for consumer grade products
well invested 20000EUR

4

RF, Microwave, Ham Radio / Re: High bandwidth FM signal generation

« Last post by radiolistener on Today at 05:29:07 pm »

Check out the DARPA program Computational Leverage Against Surveillance Systems or CLASS.

https://www.darpa.mil/program/computational-leverage-against-surveillance-systems

We developed the computational chip over a decade ago for CLASS.

is there any public available detailed info about used approaches in this program?

5

Beginners / Re: Why are thermal jumpers so expensive?

« Last post by tooki on Today at 05:27:57 pm »

As I understand it, SMD chip resistors are made in strips, with all steps done in strip form, and then as a final step the strips are snapped or sawed apart.

6

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

« Last post by mrisco on Today at 05:27:34 pm »

New header bar

(Attachment Link)

The "New Header" version has been released in the repo.

7

Test Equipment / Re: Second bench PSU, am I thinking about this correctly?

« Last post by KrudyZ on Today at 05:25:42 pm »

If you have the space you could pick up something like an Agilent 6624A for very little money on ebay.
This particular unit has four isolated channels and they were used in automated test equipment setups.
They do not have banana plug sockets and the UI isn't great (LCD is hard to read) as they were meant to go into test rigs or system use and were usually remote controlled.
They are of high build quality, but are obsolete, so many installations have taken them out of service once Agilent (Keysight) stopped servicing them. All of this makes them a great deal.
If you don't feel like having to repair it from the get go, you should probably not get the absolute cheapest. Look for good vendor ratings.

8

Projects, Designs, and Technical Stuff / Re: Corrosion on DIP pins

« Last post by tooki on Today at 05:25:12 pm »

I wouldn't be surprised if the caps had leaked, and the electrolyte is the reason for the rust.

9

Beginners / Re: Convert US standard 115V to International 230V

« Last post by tooki on Today at 05:23:13 pm »

but AGAIN you missed the fact that OP clarified before your first reply that the 20A input was NOT the actual maximum input current established by some empirical means, but a mystery number from a long-gone employee.

Yes, when I posted my first message in this topic, I didn't notice that he don't have other power supplies and 20A is a mystery number.
And what? This is the reason you're attacking me? 

Not attacking. Explaining our frustration.

10

Projects, Designs, and Technical Stuff / Re: Is this circuit adequate to interface a uC with a dc motor using an optocoupler?

« Last post by FBMinis on Today at 05:22:58 pm »

I re-drew the schematic, hope it's clearer.

the water dispenser is comprised of an 18650 cell, circuit board and motor. The circuit board has a uC that handles USB charging and that enables/disables the motor when its button is pressed.

I want to enable/disable the motor periodically with an ESP32C3 through an optocoupler.