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What Electronic Projects are you working On

Seed thread to start things off.

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Gordon W24/05/2014 09:57:59
2011 forum posts

This did not start out as an electronic project, but it is now. Started to wire up the trailer socket on my newly fitted towbar, realised the car is modern and has a whole load of electronic gubbins which means I need a relay of some sort. Bank holiday weekend of course. Modern motors don't you just love 'em.

John Haine24/05/2014 10:57:50
3425 forum posts
184 photos

Gordon, I gather that from June if a tow bar is fitted various car control systems have to be re-programmed so that for example the brakes adapt when towing. I heard of a case where a guy towing with an Audi had an accident that wrote off the car and the insurance claim was declined because this hadn't been done. Might be with checking out?

Gordon W24/05/2014 11:11:49
2011 forum posts

John, I've heard similar but assumed it only applied over a certain weight, but will check it out. Also just found out the towing electrics are now part of the MOT. So will have to take the socket off before testing. Sorry to go of topic so early. Still have not found a simple book that will forward me in electronic. I have come to the conclusion that there is just too much jargon, and it is assumed that even beginners know this jargon, but this is fair enough because I use words when talking about engineering or motors that most people don't know.

jason udall24/05/2014 11:24:20
2028 forum posts
41 photos
Gordon. .from the early days of mew..various simple projects in elecronics...if you can take a look....the intended audience might have coloured the approach. .thus a good place to start...
Andrew Johnston24/05/2014 11:40:28
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5726 forum posts
660 photos

Les: Thanks for the link, and I have also received the email. When I get time off from work I'll read the code in detail and extract the underlying mathematics.

I think there are two effects to take into account when simulating a natural flame; one, the natural variation in brightness, and two, variations due to external effects, like a breeze. I found an article on the internet about simulating a candle with LEDs. The article was from 'Circuit Cellar', who used to write a column in the early years of 'Byte' magazine, before it went all PC, in both senses. In turn the article references a professional paper that essentially says that the light intensity from a candle is flat up to a certain frequency, and then falls off as 1/f^2, pretty much like a single pole lowpass filter. I will be writing in C, my days of writing in assembler are long gone! The plan is to generate a uniform pseudorandom number using a linear congruential generator, although if that turns out not to be random enough I'll look at using a Mersenne twister. Then I'll use a simple difference equation to perform lowpass filtering. The number coming out of that will drive a PWM generator that controls the on/off period of the constant current drive for the LED. For simulating the breeze the original article used a thermistor, as the LED candle was intended for use on a stage, and was thus out in the open. I plan to use another, slower, pseudorandom number generator, plus possibly a Gaussian weighting, and feed that into the PWM generator too.

Regards,

Andrew

Neil Wyatt24/05/2014 12:02:24
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Hi John,

I've made an AVR speed controller for my loco, with a remote control box with a an LCD readout. It's got the outputs for a solenoid 'brake' (the brakes move but the real braking is back-emf) and for a horn/engine sound speaker when I get round to coding the sound generation.

I've made a few other FET based motor controllers, all PWM and fairly modest current capacity. They just get simpler and simpler with tougher FETs and cleverer micros.

Is it worth starting a thread on this topic?

Neil

P.S. is it ever possible to have too many 100nF capacitors - I can't find ONE! AGAIN!

Michael Gilligan24/05/2014 13:59:37
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16637 forum posts
724 photos
Posted by Neil Wyatt on 24/05/2014 12:02:24:

... I've made a few other FET based motor controllers, all PWM and fairly modest current capacity. They just get simpler and simpler with tougher FETs and cleverer micros.

Is it worth starting a thread on this topic?

Neil

.

Definitely !!

.... Especially if anyone can contribute regarding adaptations for high current use.

MichaelG.

Andrew Johnston24/05/2014 14:47:56
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5726 forum posts
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Posted by Michael Gilligan on 24/05/2014 13:59:37

.... Especially if anyone can contribute regarding adaptations for high current use.

MichaelG.

Depends what you mean by high current? I'm comfortable with power semiconductors and their drives running at hundreds of volts and hundreds of amps. And I know of at least one person on this forum who knows way more about power electronics than I do.

In my photo albums, under 'Semiconductor Devices', there are some notes on the characteristics and foibles of semiconductor switching devices.

Regards,

Andrew

Michael Gilligan24/05/2014 16:48:15
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16637 forum posts
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Posted by Andrew Johnston on 24/05/2014 14:47:56:
Posted by Michael Gilligan on 24/05/2014 13:59:37

.... Especially if anyone can contribute regarding adaptations for high current use.

MichaelG.

Depends what you mean by high current? ...

Regards,

Andrew

.

Thanks, Andrew,

I suppose that was a "how long is a piece of string" sort of comment. blush

... What I meant was anything an order of magnitude or two up from Neil's "fairly modest".

MichaelG.

Andrew Johnston24/05/2014 16:59:39
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5726 forum posts
660 photos
I suppose that was a "how long is a piece of string" sort of comment. blush

... What I meant was anything an order of magnitude or two up from Neil's "fairly modest".

MichaelG.

Which still leaves me in the dark, as I don't know what Neil regards as modest. smile o

Andrew

Neil Wyatt24/05/2014 17:06:54
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18320 forum posts
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My 'fairly modest' is about 8 amps stall current, but designed to handle up to about 30. Full 8Atand the heat sink doesn't even start to get warm.

Anyways, I've started a thread for motor controllers, so this one can stay general.

Neil

jason udall24/05/2014 17:11:55
2028 forum posts
41 photos
Re flickering. .
Do you really need to generate pseudo random on the fly?..
A long enough sequence in rom would do....
Or noise diode into a/d pin....but fixed sequence .or two sequences of differing lengths. ...
But hey its your thing...
Just a thought..the guys designing the original lamps strove to make the lamp as flicker free as possible...and now we take a perfectly good light source and much it up to make it more" real" we are truly mad
Michael Gilligan24/05/2014 18:02:22
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16637 forum posts
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Posted by jason udall on 24/05/2014 17:11:55:
we are truly mad

.

Quote of the Day, Jason.

MichaelG.

Michael Gilligan24/05/2014 18:03:43
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16637 forum posts
724 photos
Posted by Neil Wyatt on 24/05/2014 17:06:54:

My 'fairly modest' is about 8 amps stall current, but designed to handle up to about 30. Full 8A tand the heat sink doesn't even start to get warm.

Anyways, I've started a thread for motor controllers, so this one can stay general.

Neil

.

Thanks, Neil

MichaelG.

John Stevenson24/05/2014 18:05:40
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Posted by Andrew Johnston on 24/05/2014 14:47:56:And I know of at least one person on this forum who knows way more about power electronics than I do.

Regards,

Andrew

.

Aahh you must mean Flash Gordon ?

Neil Wyatt24/05/2014 18:26:13
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18320 forum posts
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Hi Andrew,

If you are using Arduino, drop in this AVR code. It's an exact implementation of the random function used in BBC Basic IV. The random number is a 5-byte integer in temp:temp4 and index should be set to 0x04 on entry.

Neil

RANDOM_LOOP:
;we run this four times to create the next random number (BBC BASIC IV Pattern)
ror temp4
mov X_reg,temp3
ror temp3
mov temp4,temp3
mov temp5,temp2
mov temp3,temp2
lsr temp5
eor temp5,temp1
andi temp5,0x0F
eor temp5,temp1
ror temp5
ror temp5
ror temp5
ror temp5
eor temp5,temp4
mov temp4,X_reg
mov temp2,temp1
mov temp1,temp
mov temp,temp5
dec index
brne RANDOM_LOOP
ret

Bazyle24/05/2014 18:52:24
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5567 forum posts
207 photos

Learning electronics : We have beginners machining series in MEW and ME. Stands to reason the electronics mags like Practical Electronics do the equivalent. I based my career on what I learned from 3 issues in 1969 as my degree is not in electronics.

Neil Wyatt24/05/2014 19:20:02
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18320 forum posts
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I was given a photocopied series from Practical Electronics on an introduction to logic, and my dad was happy to order me as many free datasheets from RS as I wanted with each order. For some reason he was less happy about me ordering big chips..

I still have a ZN104E that's about 35 years old, now relocated into a crude frequency counter/generator with one of those sine/square/triangle chips.

Two books I still use for non-logic stuff are Michael Tooley's Maplin Electronic Circuits Handbook and a battered copy of The Art of Electronics first edition, that I discovered 20 years too late.

Neil

Andrew Johnston24/05/2014 20:44:08
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5726 forum posts
660 photos

Here is a PCB I did earlier, in fact over 15 years ago, names blurred to protect the guilty:

pcb_front.jpg

And t'other side:

pcb_rear.jpg

There's not a single thru hole component on the board. You can tell it's a bit old hat though as a lot of the ICs that are not BGA have leads. smile o And the standard passives are 0603, which is bit large these days. There are some quite big gaps on the PCB and large SM capacitors, these are for isolation of the two telecon lines, one for a telephone and the other for a modem. I can't remember if the board was 6 or 8 layer, but to cope with the fine pitch BGAs and tracking density we used laser drilled blind vias in the pads and buried vias. Pretty expensive technology for what was intended to be a consumer product. I didn't design the discrete 2.4GHz Bluetooth transceiver inside the silver shield. Of course these days it would all be on one RF IC. The best part about the whole project was that I spent about 18 months working on and off in Holland, all on expenses. smile p

I'm not sure that the electronics magazines these days do beginners articles? When I was taking electronics magazines in the 1970s each article started with a detailed circuit description. Then the description was simplified and put in a box at the side of the article, so it could be skipped. Then it got missed out all together. Probably the best bet is to obtain old copies of Everyday Electronics or Practical Electronics and follow the beginners articles within. The Everyday Electronics ones worked for me!

Jason: Thanks for the idea on random number generation. But it is much simpler to generate via the equation. It's one line in 'C' and will generate a far longer sequence than I could store in an IC. And it means I don't need the IC.

Neil: Interesting code, the processor I am going to use is native 32-bit internally, a 32-bit integer should be large enough to generate a reasonable sequence.

Note: High level language compilers are way better than they used to be - the last high power inverter I designed ran all the code switching the IGBTs (at 10kHz) and doing the Park-Clarke transforms in C, albeit on a floating point DSP.

Regards,

Andrew

Neil Wyatt24/05/2014 21:47:10
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18320 forum posts
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Afraid my homebrew boards don't quite measure up to that, Andrew. Especially after I lifted tracks turning chips round...

Still a work in progress this one! Basically its a 128K ram 8-bit computer running a virtually complete version of BBC BASIC IV (although I'm technically not allowed to call it BBC BASIC, let's say it's highly compatible) with a full colour 1/4 VGA display using an extended set of the BBC VDU commands as per the BBC Master (so with higher level graphic primitives like circles, triangles etc.)

The current bugbear is the lack of a filing system - the amstrad email mini-keyboard is fun and fits with the size of the thing, but I usually write test programs on the PC and upload them via the on board USB-serial.

I haven't done any development for about 18 months, I do mean to make a fully OSFILE compatible filing system using SD cards but every time I have a go I get distracted by other bits, such as debugging the onscreen editor so I don't have to use the ghastly BBC line editor.

Neil

 

<edit> Oh my golly gosh! I hadn't realised just how ghastly that PCB is.

circuit.jpg

Edited By Neil Wyatt on 24/05/2014 21:49:13

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