JohnsUPS
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Re: Learning Electronics

Sun Apr 07, 2019 4:18 am

Wow, this thread takes me back.

I also built a crystal radio on a small board. Mom wasn't happy when I nailed it to the bedpost so I could listen to the radio at night. Stringing the long antenna wire from the upstairs window was met with a similar reaction.

At some point had one of those project kits with the springs. From there it quickly went to the books from Radio Shack by Forrest M. Mims. Experimented with a lot of those circuits for sure. Learned a lot about the 555, LM317 and basic digital logic. :D I still have many data books from National Semi, International Rectifier, Analog Devices and so forth, but they have all been supplanted by Google. I have both editions of the Art of Electronics - still the best and a handy formula reference.

I also experimented with photo developing PCBs. Even sprayed the bare boards with the photo sensitive coating. I don't think you can buy that stuff any more - must have been found to cause cancer in lab rats or something.

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rpdom
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Location: Chelmsford, Essex, UK

Re: Learning Electronics

Sun Apr 07, 2019 5:57 am

JohnsUPS wrote:
Sun Apr 07, 2019 4:18 am
I also experimented with photo developing PCBs. Even sprayed the bare boards with the photo sensitive coating. I don't think you can buy that stuff any more - must have been found to cause cancer in lab rats or something.
Currently I'm experimenting with with an iron-on (UV) photo sensitive layer and copper chloride etchant. I haven't produced a working board yet, but it is looking promising. (This is a side-project and I'm not spending much time on it).

Heater
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Re: Learning Electronics

Sun Apr 07, 2019 7:13 am

JohnsUPS,
Wow, this thread takes me back.
They were great times weren't they? From crystal sets to tube radios to Philips Electronic Engineer Kits to transistors to 555 timers to 7400 TTL chips to micro-processors... All in one childhood!

Image

Do try to keep up though. TAOE is now on it's 3rd edition:
https://artofelectronics.net/

Now a days I build my 555 timers out of discrete transistors:
https://shop.evilmadscientist.com/productsmenu/652
Memory in C++ is a leaky abstraction .

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Burngate
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Re: Learning Electronics

Sun Apr 07, 2019 9:01 am

M. G. Scroggie, "Foundations of Wireless" (1936) updated to "Foundations of Wireless and Electronics"
Bought the 8th ed. in 1971 (though I'd borrowed an earlier edition from the library earlier)
And it's available now as a PDF

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Burngate
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Re: Learning Electronics

Sun Apr 07, 2019 9:12 am

And just to come back to the present, I still think a basic understanding of electricity (voltage, current, resistance, capacitance, inductance) followed by how semiconductors work (diodes, transistors of both sorts) is advantageous today.

As a separate thread, logic gates should be understood; how a register works; why dynamic ram is an abomination that's also ubiquitous; ...

Heater
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Re: Learning Electronics

Sun Apr 07, 2019 10:25 am

Burngate,
M. G. Scroggie, "Foundations of Wireless"...
Oh my God, I had completely forgotten Scroggie. He was my permanent companion for years as a young teenager.

I agree, judging by the questions that come up here often it sounds like a basic grounding (pun intended in electricity is missing for many now a days. Heck I'd just call it "physics", it was all part of our high school education, known as just "science" back then.

Why is dynamic RAM an abomination?
Memory in C++ is a leaky abstraction .

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Burngate
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Re: Learning Electronics

Sun Apr 07, 2019 10:50 am

Static ram holds its values indefinitely, but dynamic ram needs periodic refresh. While it's doing that, the processor is spinning its heels waiting, so you have no idea about timings.

Heater
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Re: Learning Electronics

Sun Apr 07, 2019 11:40 am

Burngate,
Static ram holds its values indefinitely, but dynamic ram needs periodic refresh. While it's doing that, the processor is spinning its heels waiting, so you have no idea about timings.
Yes but:

Modern CPU's can consume instructions and data 10 or 100 times faster than any kind of RAM can deliver it. Dynamic RAM refresh cycles consume less than 1% of the time. So without anything else the impact of refresh does not even show up in the noise timing wise.

The "something else" is of course one or more layers of fast cache memory between the CPU and the main memory. Plus the fact that RAM is read in blocks rather than word by word. The upshot being that dynamic RAM refresh times have a vanishingly small impact on performance actual timing determinism.

So, if you want performance and large memory dynamic RAM and cache is the way to go at this time.

You are right, if cycle by cycle timing determinism is what you want then you have to go to static RAM and throw away the block access and cache. You will also want to get rid of branch predictors and speculative execution. But then your performance will be orders of magnitude less. That is micro-controller territory.
Memory in C++ is a leaky abstraction .

Andyroo

Re: Learning Electronics

Sun Apr 07, 2019 12:01 pm

The other advantage of dynamic RAM is the cost :roll:

Saying that though - I’ve been watching Julian Ilett build his 8-bit Komputer with static ram and that’s got me itchy for a big project at home.

Maybe a software defined computer first then move it to hardware - will teach me lots about TTL.

Heater
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Re: Learning Electronics

Sun Apr 07, 2019 12:14 pm

Oh yes, forgot the cost.

Last I heard Julian called his TTL breadboard Komputer "Oink" because it's a One INstruction Komputer.

Writing a software emulation of your intended computer is a great idea. One potential problem is that it's very easy to write in software something that might be huge and complex in actual TTL chips.

If you are going to do that I would suggest writing your computer's logic in Verilog, a hardware description language, and then simulating it with the Icarus Verilog compiler/simulator.

https://learn.sparkfun.com/tutorials/pr ... ic-verilog
https://iverilog.fandom.com/wiki/Simulation

You could even then turn your design into hardware ona 10 dollar Lattice FPGA using the open source Yosys tools:
http://www.clifford.at/yosys/
http://verilog.james.walms.co.uk/
Memory in C++ is a leaky abstraction .

Andyroo

Re: Learning Electronics

Sun Apr 07, 2019 12:21 pm

:shock:

I did a bit of work in Forth for finite state machines and wrote cross compilers (and the odd micro Forth) many many years ago but that may well be a bit beyond me as I’m still at the ‘blowing up’ electronics stage so far...

:lol:

Heater
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Re: Learning Electronics

Sun Apr 07, 2019 1:14 pm

Yikes, anyone who can handle Forth can handle pretty much anything. Gives me headache.

If you understand state machines then your are good to go with hardware design in Verilog.

Hey, when does anyone stop blowing up electronics? :)
Memory in C++ is a leaky abstraction .

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bensimmo
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Re: Learning Electronics

Sun Apr 07, 2019 1:22 pm

Basic electronics concepts are in KS2/3 and GCSE science
Voltage/Current/Resistance
A bit later they get the electromagnetic effect.
At A-Level if they choose Physics they get resistivity, capacitors, emf and some concept based around that.
They may get more at A-Level Physics if the teacher chooses that as the additional module (though Astrophysics tends to be the easier one to do)

They used to have logic gate *basics*, but that now in Computer Science or some other optional GCSEs.
Still they may have done it when they played with switches.
The OpAmps, Timers don't see the light of day, even then for early 90s people, that would only have been an Electronics GCSE as it would now.
It's not deemed as being needed, u less you specialise. Aka the government doesn't need you ;-)

I think some of you should go see/read what they actually teach. Just because the kids don't remember or have any interest, doesn't mean they don't do it.

In the same way, just because you had interest and remember doing it, doesn't mean the majority of people did.

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bensimmo
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Re: Learning Electronics

Sun Apr 07, 2019 1:28 pm

W.r.t. the Foundation.
They have had a series on electronics in the HackSpace magazine they produce.

But as the site and especially the forum is more RP Trading based at the moment, you'll not find them or talked about much.
Maybe they'll get down of the series up into the Projects side of the site.

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bensimmo
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Re: Learning Electronics

Sun Apr 07, 2019 1:31 pm

Saying that, it seems some are there, there is just no way of finding/searching for them from the projects part.



https://projects.raspberrypi.org/en/projects/halfadder
Via
https://hackspace.raspberrypi.org/projects

Heater
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Re: Learning Electronics

Sun Apr 07, 2019 2:05 pm

Never mind all the electronics, I'm going to build myself a trebuchet:
https://projects.raspberrypi.org/en/projects/trebuchet
Memory in C++ is a leaky abstraction .

Andyroo

Re: Learning Electronics

Sun Apr 07, 2019 2:45 pm

Heater wrote:
Sun Apr 07, 2019 2:05 pm
Never mind all the electronics, I'm going to build myself a trebuchet:
https://projects.raspberrypi.org/en/projects/trebuchet
Please stick to tennis balls and not haggis

Interesting thought though - maybe the Foundation could get the Men’s Sheds Groups to lead an electronics introduction? The local shed is really woodwork oriented and the Maker site is still limiting numbers as they are newly opened and electronics is a minor part of their remit...

Heater
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Re: Learning Electronics

Sun Apr 07, 2019 4:14 pm

A man's shed is where he uses dangerous machines, drinks beer and uses bad language.

Not really the place to be teaching electronics inclusively. Except to future men of course.
Memory in C++ is a leaky abstraction .

boyoh
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Location: Selby. North Yorkshire .UK

Re: Learning Electronics

Sun Apr 07, 2019 10:22 pm

rpdom wrote:
Sun Apr 07, 2019 5:57 am
JohnsUPS wrote:
Sun Apr 07, 2019 4:18 am
I also experimented with photo developing PCBs. Even sprayed the bare boards with the photo sensitive coating. I don't think you can buy that stuff any more - must have been found to cause cancer in lab rats or something.
Currently I'm experimenting with with an iron-on (UV) photo sensitive layer and copper chloride etchant. I haven't produced a working board yet, but it is looking promising. (This is a side-project and I'm not spending much time on it).
Just one point when marking your circuit on the copper
Side of the PCB . Mark it in reverse, remember the components
Are on the other side
Regards BoyOh
BoyOh ( Selby, North Yorkshire.UK)
Some Times Right Some Times Wrong

Heater
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Re: Learning Electronics

Mon Apr 08, 2019 4:11 am

Good point about the reverse PCB layout. It's one of those silly mistakes that catches people to often.

On PCBS:

I recently discovered that using surface mount components can be easier than through hole. My first SMD experiment was just a board with a bunch of resistors and LEDS. To my surprise the bigger SMD parts are pretty easy to get soldered down. There is no fiddling with drilling hundreds of holes, poking wires through and trimming leads. Neat and quick. Even a lot of SMD chips are fairly easy to solder by hand. Even with my terrible eyesight a jewelers loupe and a bright light gets the job done.

Whist I think every one should have a go at making a PCB by hand, just for the fun and getting an appreciation of the technology, now a days I would suggest getting the boards made by a PCB house. It's pretty easy to get simple boards laid out with KiCad and a place like JLCPCB will make the boards amazingly cheaply and quickly. In fact quicker and cheaper than if I collected everything I need to do it by hand.

http://kicad-pcb.org/
https://jlcpcb.com/
Memory in C++ is a leaky abstraction .

boyoh
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Re: Learning Electronics

Mon Apr 08, 2019 7:50 pm

This is one project one could find very us full for learning electronics
All built on Vero Board Good for learning to solder
Incorporating all pins from the Pi , also 4 slotted Opto Isolators
Witch I could beam brake manually and electronically for testing, All GPIO pins can be connected to the breadboard using jumper wires
Breadboard power supply using 0 / 12vdc 4amp Fuse protected
Building this is all part of the learning curve

Regards BoyOh
Pi Board  IF 010.jpg
Pi Board IF 010.jpg (47.98 KiB) Viewed 1333 times
Pi Board  IF 010.jpg
Pi Board IF 010.jpg (47.98 KiB) Viewed 1333 times
BoyOh ( Selby, North Yorkshire.UK)
Some Times Right Some Times Wrong

Heater
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Re: Learning Electronics

Mon Apr 08, 2019 8:38 pm

I like it.

This could be developed into some kind of kit of parts for beginners tinkering with electronics. With various simple sensors, opto's transistors, MOSFETs etc. All nicely packaged up with some tutorial materials and little projects/experiments.

Soldering required of course.
Memory in C++ is a leaky abstraction .

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Imperf3kt
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Re: Learning Electronics

Mon Apr 08, 2019 10:09 pm

I cant make sense of it from the pictures. Probably warrants some explanation / circuit diagrams.

And is that a Pi1b?
55:55:44:44:4C
52:4C:52:42:41

JohnsUPS
Posts: 127
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Location: USA

Re: Learning Electronics

Mon Apr 08, 2019 11:06 pm

Do try to keep up though. TAOE is now on it's 3rd edition:
https://artofelectronics.net/
Oops....I was thinking the silver edition was the first....should have looked behind me on the shelf and checked the revision #. I bought the third edition as soon as I saw it....

I think most people only make the mirror image PCB mistake once. :lol:

I had a job in an engineering lab where I got to build prototypes of brand new designs/circuits/products from scratch from nothing more than a schematic (or part of one to test a section). Awesome creative opportunity. Mostly analog stuff. This was the era when SMD was first becoming commonplace, so where applicable and appropriate, I'd mix through hole and SMD parts. At the level of prototyping that I did, this was the pre-PCB stage of design - basically a build-it-to-see-how-well-it-works stage.
I still build my projects using the tricks learned when designing these prototypes. It makes stuffing 10lbs of electronics into a 5lb box possible. :D

Heater
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Re: Learning Electronics

Tue Apr 09, 2019 7:40 am

Imperf3kt,
I cant make sense of it from the pictures. Probably warrants some explanation / circuit diagrams.
Well let's see...

Top left is an old Raspberry Pi of some kind.

Top right is a USB hub with some memory sticks in it. I guess that does not need explaining.

Bottom Left is a big brown piece of Vero Board. That is an old style printed circuit board made of Paxolin. It has a matrix of 0.1 inch spaced holes for poking wires through or the leads of components. Perfect for 0.1 inch pitch logic chips. On the underside of the board are stripes of copper track running north-south that the wires/component leads can be soldered to, thus allowing one to build circuits.
See here: https://en.wikipedia.org/wiki/Veroboard

There is a big grey 40 way ribbon cable connecting the GPIO header to a connector soldered to the Vero board.

Below that we see a couple of rows of jumper pins solder to the board, then a nice area of jumper pins with coloured labels telling the pin numbers, sweet.

Below that we see a row of four slotted optical sensors. Just LEDs shining across a gap to photo diodes, mounted in black plastic cases.

Bottom right is a white "bread board". Again an 0.1 inch pitch matrix of holes for wires component leads. This time the holes contain spring clips to hold the wire ends, no soldering required. Thise clips are electrically connected horizontally in rows of 5.

So, what we have here is a neat way to quickly build up a circuit with chips, transistors, whatever components on the white bread board. Then connect the inputs and outputs of that circuit to the neatly labeled GPIO pins seen on the Vero board using jumper wires.

All in all there is no "circuit" there to diagram. Just the space, mechanical stability and connectivity to enable you to build your own circuits experiments quickly. Which of course is the whole idea.

As it happens I have been eyeing up a 40 pin ribbon cable and piece of Vero board I have with a similar notion. This gives me some ideas....
Memory in C++ is a leaky abstraction .

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