Recent Posts

1

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

« Last post by strawberry on Today at 06:57:26 pm »

in case NAND chip is readable someone may try to copy contents
something like this

2

Beginners / Re: The old "Replace blue LEDs with red LEDs" 7 segment question (74HC595)

« Last post by xvr on Today at 06:56:42 pm »

> the 595 could be replaced with a stronger version

They could (tpic6(a/b/c)595). But they has different package, not compatible with PCB for 74HC595. And different pinout.

3

General Technical Chat / Looking for reverse osmosis with less than 25% waste

« Last post by Miyuki on Today at 06:53:09 pm »

Are there any people with knowledge about reverse osmosis?

I know some industry-scale systems can do this. But I want it with a small (medium) system with a rate of demineralized water of about 1 l/min.
It will be fed with relatively highly mineralized ground water (plenty of Mg and Ca). And I do not like to throw plenty of water to waste.

Do any of you have some experience with it?

4

Microcontrollers / Re: Routines to convert binary to BCD in C code

« Last post by cv007 on Today at 06:51:49 pm »

and dumped the count by UART every second

That is one of the points I am making- speed of conversion does not matter at all if outputting only every second. Even when you want to dump lots of (formatted) data it matters very little.

You original post was focused on the conversion speed, but if you had actually output all the data at your specified 9600 baud (960 bytes/sec) you would have found out that any formatting you can come up with will be blocking on the uart as it sends out the data, whether you used the arduino print which you had access to or your own custom bcd conversion.

Do what you desire, but using existing code for formatting such as printf or arduino print will be plenty fast. Code size will also be of little concern unless you have a 4k or less mcu. In the case of an avr, the printf code is about 1.5k and once brought in you can use it as much as you want (so use it for everything that needs formatting). For arduino (which I don't use) I imagine no one using that will concern themselves with how the details of formatting are done as they just use print when the need arises.

printf( "%lu\n", my10MHzCounter() ); //%lu for 32bits on avr
Serial.println( my10MHzCounter() );

5

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by gf on Today at 06:51:03 pm »

What is the length of your Lanczos filter?

well this is quite embarassing iirc i set "wing" length as small as possible due to some complication i encountered earlier, extra ringing? iirc... length only like 2 or 3 i dont have indepth knowledge about it and its effect. thanks for your info, i'll looking into it deeper later...

With a single-sided length of 3 (double-sided length 6), you should be able to reconstruct up to ~140 MHz at 500 MSa/s with less than 1% interferences.

I just don't know if you measure the length in the same way as I do, therefore I have added the plots to show what I mean with lenght 3.

6

Beginners / Re: Bulk input caps and impedance

« Last post by xvr on Today at 06:49:26 pm »

If I put a cap directly across a DC barrel jack input, then when I connect the power to it, I will get a spark

There is should not be with simple capacitor. Especially with 220uF. Something definitely wrong. May be capacitor was plugged in reverse, may be rated voltage of capacitor is much less that PSU output.

Normal PSU should not even notice capacitor of such value.

7

RF, Microwave, Ham Radio / Re: RF Test Automation

« Last post by vino on Today at 06:47:19 pm »

For now my focus is testing and characterizing RF Power amplifiers. I want to automate the measurement of each parameters.

Again, do you know which parameters you want to measure? Measuring different parameters may require different test equipment and different test setup. I'd think full automation of measuring all amplifier parameters under the Sun will require an elaborate test setup on the bench, and that even before using SCPI.

These are the parameters that I'm interested in automated testing.
1. Gain
2. Gain Flatness
3. IMD
4. Psat
5.P1dB
6. Spurious

I know how to test them manually and I'm also confident in using the equipment and tools to test them.
I just want to take advantage of capability of the programming language such as Python to make my work easier. By incorporating test automation.
Modify message

8

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by Mechatrommer on Today at 06:44:21 pm »

What is the length of your Lanczos filter?

well this is quite embarassing iirc i set "wing" length as small as possible due to some complication i encountered earlier, extra ringing? iirc... length only like 2 or 3 i dont have indepth knowledge about it and its effect. thanks for your info, i'll looking into it deeper later...

9

Projects, Designs, and Technical Stuff / Re: Small and inexpensive direct thermal printer to print labels

« Last post by Perkele on Today at 06:43:36 pm »

These guys had reasonably priced printers when I was using them:
https://www.custom.biz/en_GB/product/hardware/printers/kiosk-receipt-printers/kpm180h

Most of them use ESC/POS or some kind of "binary" comms protocols.
ESC/POS is supported on multiple platforms, would not be surprised if someone also did an Arduino library for it.

10

Repair / Re: Roberts DAB radio ECOLOGIC4 / RD21 / RD-21 no sound / will not switch on

« Last post by nfmax on Today at 06:41:31 pm »

I'm happy to say I have been able to repair the fault! I removed the CD4013 (IC5) using the 'soldering iron & pry' technique, as I didn't want to have to unsolder the immediately adjacent on/off switch to allow the use of hot air. This was a mistake, as the chip was glued to the PCB . Still, it eventually came off OK. I replaced it with a new part, and replaced R4 with a series combination of 100Ω and a BZX84C3V3 zener, which I happened to have in stock. Gradually winding up the supply voltage showed the Vdd supply still reached 18V with only 218VAC at the input - clearly the zener was not dropping enough volts at the very low operating current.

There is an unpopulated 0603 footprint 'R69' across the Vdd rail smoothing capacitor, so I fitted 3k3 in this position. This should give somewhere around the 5mA zener current required for correct operation. Vdd now measured 16.5V at 240VAC input - outside recommended working range, but well within the absolute maximum. Dissipation in R69 is comfortably less than its 0.1W rating. The set now draws approximately 1.0W from the mains supply in 'off' mode.

Unfortunately, it also draws about 1.7mA continuously from the batteries, when the mains lead is disconnected. Enough to completely drain them in about 12 months. As this is someone's 'kitchen radio', I doubt if it has ever had a set of batteries installed, but I will provide a warning anyway.