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EEVblog Specific / Re: EEVblog #1015 - Beware Evil (But Clever) DC Jacks
« Last post by Brumby on Today at 09:53:00 PM »
That's it.

There are ones with isolated switching - but you would have to look a little harder to find them.
EEVblog Specific / Re: EEVblog #1017 - Enter The World Of Atto Amps
« Last post by pmcouto on Today at 09:45:09 PM »
Keithley 6172 is a 2 slot male to 3 lug female Triax adapter.
But it’s not cheap…

I bought one of these adapters from Farnell a few months ago.
According to the information on Farnell's website today, they have 14 units in stock.

Pedro Couto
Beginners / Re: Why is "19.5V" used as a common laptop charger voltage?
« Last post by KL27x on Today at 09:44:41 PM »
I find it convenient, because it's the most voltage I can get without sticking zeners on my FET gates. Maybe laptop charging circuitry is simplified for this same reason. If you search power FETs and look at Vgs, you will find 99% of them have max Vgs of +-20V.

There's quite a detailed answer to this here


Most laptop batteries don't exceed more than four series cells, cells having a maximum safe charging voltage of 4.2V = 16.8V maximum for any series of cells. Input voltage is slightly higher to accommodate the charging circuitry.
Yeah but it is rarely "tool x vs no tool x" but "tool x vs getting something else, possibly more useful"

Like if you need "a tool to experiment with filters" (in near-audio range I assume, based on "breadboard), something like Analog Discovery will give you way more bang per buck as it:

* can start from lower frequency
* built-in generator
* built-in power supply (so you can just connect all wires from your project to same box

Or as others mentioned, just a scope + generator, as both of them are immensely useful

And when you will need the spectrum analyzer, you'd at least played with one enough to know what exactly you want
Hi Ron,

The schematic in your post just contains a small part of the project. Is the full schematic avaiable somewhere? Did you produce PCB's, and are these available?

I'd love to build one!

Best regards,

Renewable Energy / Re: Where does the power go ?
« Last post by IanMacdonald on Today at 09:33:33 PM »
Basically there is only limited storage capacity on the Grid, so generation has to be matched to demand as an ongoing process. In the UK anyway, the frequency is used as a means of signalling over or under supply. If it gets a bit below 50Hz then all contributing stations will tend to ramp their output up. Not sure if other Grids use this principle or not.

When heavier loads are anticipated, extra stations are asked to become 'spinning reserve' -That is, turbines revolving and synced-up bit not delivering any significant output. Thus they can quickly come onstream to cope with demand. If it turns out their services aren't required, the operators get paid 'constraint payments' for the fuel used to spin-up needlessly.

The controversial aspect is that renewables operators also get constraint payments, only in their case  it's for all energy which could have been delivered even if no-one could possibly have wanted it.

Nuclear cannot vary its output rapidly, plus the main costs are the fixed ones, whilst the fuel is cheap. Thus it makes financial sense to run nuclear stations at full power as much as possible.

The main source of reserve in the UK is combined cycle gas turbine plant. Although this can come onstream very quickly it takes time (an hour or so) for the secondary steam cycle to start up, and that means accepting a significant reduction in efficiency under start/stop operating conditions. 
Hi Ron,

In 1976 me and some frined started building our own Motorola 6800-based computer. Some later, we built a Mark II based on the 6809. It is the best microprocessor for assembly programming EVER!

We built the 'OS' ourselves, and reverse engineered an assembler and editor and a BASIC interpreter from hex dumps. Those were the days.

I've been looking for a single-board 6809 based microcomputer to relive the old days, and would love to work with you on the software, if you're still looking for help in that department.

Just drop me a line if you're interested.
What Ram and eeprom are you using now?


I liked wordstar as my editor. could make documents and write source code with it.

There are many Assemblers
  Some are relocating macro assemblers.

From microsoft there was M80 assembler
L80 is a linker so you can link different assemblys together.
many others.

You could do all your programming & testing on the Z80.

Now If you can modify Cbios you could get CP/M3 running and have a larger space for programs.
You could also modify Cbios and get turbodos running. This is a networking system
Both CP/m3 & turbodos want more memory.

In monitor rom
you have capability of download of intel hex format programs.
You just write your programs so they exist in ram.
ORG 4000h I think is your ram start location.

If you modify your hardware
  You could have writable ram starting at 0H with reads from eeprom at boot.  A simple program could then read from rom and write back to same address making a copy of eeprom in ram.  You could then switch reads to come from ram.
The programs you are writing could then modify ram when needed.
A 74xx273 is the chip to use for this.

I would not mess with PSG for IO ports, You can do a Port with a 374 very easy.
This would be a faster port then PSG with nothing but an IN or OUT required for software.
If you want or need interrupts for an IO port a PIO would be best choice. A 8255 will also work but will need help for interrupts.

As long as monitor.asm code does not go up to 2000H you should be fine.

You can change the SIO vector with little problems
Do following
1. put an .org 100 before serialInt.  The serial int code will now start higher at 100.
    This change will not effect anything  but leave more unused space before this code.

2. With NMI starting at 66h, would be smart to use vectors higher then this so that future NMI code will have some space.
    Need to make two changes in code to keep SIO interrupt vector working
     A. change the vector you write to SIO
     B. Position the
          "DW serialInt" at vector address.
  If you write F0H to SIO as a vector address the above DW is at 00F0H
  If you write 80H to SIO as a vector address the above DW is at 0080H
That is all there is too it.

Note that you can change the I regester which moves the interrupt vector table.
  If you write F0H to SIO as a vector address the above DW is at (I register value)F0H
  If you write 80H to SIO as a vector address the above DW is at (I register value)80H
If i = 2 then example for vector F0H above DW is at 02F0H

Now I am not a fan of PSG.
But how you write your program can make a big difference.

Look at grant's "initialixe SIO" code.
This is simple code but hard to change using a program. If the data is in a table then much easer to change

This is the data sent to SIOA_C

Code just needs to output these bytes to the port.
You could have a byte that specifys the number of bytes
Z80 has an instruction to do this easy.

When you go to programming your PSG having data separate from code would make things easer.

This is using a CPU for what it is good at, processing data.

I've been involved in advertising for and recruiting engineers over the last 40 years in the UK, Hong Kong and to some extent India. Timing seems to be the biggest factor in a candidate's chances. We've advertised in a major newspaper and got zero to a very few replies. A few months later the same ad in the same paper has resulted in sackfuls (or their electronic equivalent) of replies. When we got only one or two replies, and really needed to fill the vacancy, a candidate's chances of being recruited were really good, if they just met minimum criteria. When we got sackfuls of replies we were able to be very choosy, although we could well have missed to best candidate in the deluge.

Of course, if the electronics industry in your area is dying, there might never come another tight labour market. Don't be too despondent, though. A dying industry makes lots of people completely abandon it, so the active labour market for the required skills might not be as loose as you expect.
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