What Electronic Projects are you working On

[MuzzerParticipant @muzzer]

That Airbus story as recalled seems to have been passed through the "Daily Mail Science Correspondent" filter. I'm not an aviation expert but even so I recall there were a few more details to the plot. I seem to recall they were both disoriented and weren't even aware the plane was in danger of stalling until too late. A mechanical coupling wouldn't have made the slightest difference. IIRC there had already been reports of problems with the Pitot tubes icing but nothing was done in time

As for cars being somehow controlled over Bluetooth and going doolally, I don't think you would believe how many layers of safety and redundancy there are in modern cars. Apart from the schadenfreude from the US car companies over the supposed problems with Toyota's throttle pedals (which turned out to be mostly false reporting and hysteria), I don't recall hearing of lots of issues with robustness on the engine control front. Cars nowadays are far less likely to suffer from loss of control than in the good old days (sticking throttle cable, anyone?) and nobody is about to throw all those babies out with the bathwater. Makes for an easy chortle down at the pub but quite simply there is no likelihood of that ever happening.

Murray

[Anonymous]

Posted by Neil Wyatt on 07/06/2014 15:24:02:

Hi Andrew,

What you end up with sounds suspiciously like a Class-D audio amp…

As for the cost of getting into 'black boxes' Arduino Uno is £49+VAT bundled with breadboard and enough components for anyone to get started, from CPC.

Neil

Good point, the output of a class D amplifier is akin to a buck converter with synchronous rectification. However I suspect that there are some subtle differences in the control and feedback circuits. Despite the novelty of being able to amplitude modulate the PSU output, in my application the important factors are DC accuracy and stability; possibly not so critical in an audio amplifier.

When I was talking about black boxes, I was referring to ICs rather than devkits, and was commenting that very few people really understand what goes on inside the IC, even simple ones. Certainly within the professional world the devkit has assumed new importance. A combination of complex processors and short timescales means it is not possible to understand everything in detail, so a devkit is very useful for getting ideas on how the darn thing works, and how to make external connections. Modern processors have datasheets and reference manuals ranging from hundreds to thousands of pages. That's a lot of reading, and even then some things are not clear. The main bugbears are reset procedures, power supplies and sequencing, and multi-function I/O pins.

Regards,

Andrew

[Cornish JackParticipant @cornishjack]

Murray – Hammer, nail, head

Rgds

Bill

[MuzzerParticipant @muzzer]

It's often tempting to believe that you can create a robust design simply by stringing together black boxes and devkits / eval boards. However, if you have no real, profound understanding of what the black boxes are doing, you are sort of hoping they do what you expect them to do. That would be nice. Unfortunately, there are often several ways for a manufacturer to achieve a given "black box" functionality and it's often essential for you to put the time in to figure out what's happening if you are to avoid those sticky moments.

As Andrew says, you can't possibly get right to the bottom of what's happening in ICs but as he mentioned there are often a few critical details hidden away in the app notes that will bite you if you don't pick up on them – and even a few that aren't! You soon learn that it's less time consuming in the end to do that homework up front than to rush the first stages and deal with the issues later. To my mind, the cost of rectifying underlying issues increases something like logarithmically, the later in the program you leave them.

Murray

[jason udallParticipant @jasonudall57142]

As to not knowing whar goes on inside the black boxes…I remember writing custom assembler to exploit undocumented op codes for both motorola and intel processors…and enjoying the re appearance of some of these (intel 808x) codes in the zilog z80.. ( explain that one)..
Best mnemonic ?…HBF..Hault and burst into flames..which is pretty much what it did. .
But yes you can’t have a micro code knowledge of every chips innards but design from data sheet should work…….

[Gray62Participant @gray62]

Posted by Neil Wyatt on 08/06/2014 15:53:14:

I came across a professional electronic engineer who used to wash boards in the dishwasher.

Neil

I amused my wife this past weekend, I had been asked to repair a laptop which had been treated to a large glass of sherry. The smell of sweet sherry was quite overwhelming and suffice to say, the laptops behaviour was somewhat erratic.

So, complete strip down, bare case in the sink with hot soapy water, along with the keyboard. The main PCB was treated to a liberal dose of a product called safeclene, rinsed with clean water and all components hung on the washing line in the sun to dry. (not sure what my neighbours thought )

Re-assembled last night and fingers crossed, applied power, SUCCESS.

I've done a few like this in the past, mostly kids throwing their can of coke over it, this was the first alcoholic laptop I've had to deal with.

Graeme

[Neil WyattModerator @neilwyatt]

You have sunshine!!! Torrential thunderstorms and hail here today

I've rescued a smartphone my daughter dropped in a river. The key action is to get the battery out fast and prevent electrolytic damage.

Neil

[MuzzerParticipant @muzzer]

Most modern electronics are washed in aqueous cleaner nowadays. Gone are the liver-destroying days of Genklene and other volatile solvents. As you say Neil, as long as you get the batteries out quickly you are likely to avoid lasting damage. Some compts like relays have breathers that might admit water but other than that, warmth and time should do the trick.

That reminds me I have an iPod that needs to go back together. It went through a full washing machine cycle and already had a broken screen but I was able to repair it with parts from Hong Kong for a few pounds. You can't remove the batteries in those quickly but we seem to have got away with it. I'm getting too old for micro surgery like this.

Murray

[Anonymous]

Posted by Muzzer on 10/06/2014 17:32:13:

As Andrew says, you can't possibly get right to the bottom of what's happening in ICs but as he mentioned there are often a few critical details hidden away in the app notes that will bite you if you don't pick up on them – and even a few that aren't! You soon learn that it's less time consuming in the end to do that homework up front than to rush the first stages and deal with the issues later.

Very true; ICs don't always do what it says on the box, or in the datasheet!

There is an art to reading a datasheet; remember that the datasheet is as much a marketing tool as a means of presenting technical data. I recall a discussion on this forum about a MOSFET datasheet which headlined a drain current of X amps. But that was at 25ºC, which implies an infinite heatsink, and later in the datasheet (in the small print!) was a note saying that the bond wires limited the drain current to X minus quite a bit.

There is also an art in deciding when to prototype a circuit to see if it does what one expects, and just going straight to PCB layout from the paper design.

Regards,

Andrew

[David Lawrence 2Participant @davidlawrence2]

" splitting a hammond organ" was something i saw happining in a music shop in 1974. Macaris in the Charing Cross road, London. The guy in the shop was using a power jigsaw just to cut through the pollished wooden case.Rather him than me. I was working for a band at the time as a roadie and our Hammond was not split and it took 3 of us to get it out of the flight case, Guitar amps are still made with valves and they seam to have kept to valve business going for the last 40 years. musicians still want old style amps built with tag strips and not pcb's. I think its a business thats keeps looking backwards at the 50's and 60's and not forward.

[jason udallParticipant @jasonudall57142]

…^… glen millar effect?

[Gordon WParticipant @gordonw]

Splitting the Hammond Organ- Can I do this to the juke box in my local pub? Do I need any special knowledge/

[LynneParticipant @lynne]

Hi there,

Attempting to get my de-humidifier operational again. Fan runs, compressor does not.

I have wired it seperately, and it runs, so I have come to the conclusion that the relay is faulty.

The relay is ' LISHENG' LRD-S-124DMT There are a lot of references to it on google, but I cannot

find a stockists. I am hoping that as many of you are involved with electronics,

you may be able to direct me to a source. Regards, Lynne

[Neil WyattModerator @neilwyatt]

Its a single pole 24V DC coil with plug in terminals, rated 7A at 250V, 12A at 125V 7A at 30V.

You know the pinout, but use a multimeter to check how the switch contacts are wired.

That should give enough information for you to source a compatible relay from somewhere like CPC – enter 'relay' into their search, narrow down to general purpose relays, then enter the above ratings in the parametric search.

You will then get a list of relays to choose from, look at the datasheets until you find one that matches the pin out.

A bit tedious, but probably not gong to take that long to do.

Neil

[ronan walshParticipant @ronanwalsh98054]

I was big into electronics as a kid (long time ago now) always working on something, but for some reason i wandered away from this line of interest. Can anyone recommend a project to get me back into the swing ?

[Gordon WParticipant @gordonw]

Ronan- I was asking similar questions a few weeks ago, you will get lots of answers. I can recomend buying an arduino board ( or a cheap clone ) mine cost about £9, Then look up "open source hardware group" and work thu' some tutorial videos, last about 10 mins each. Trouble is I found I was learning a new language as well.

[LynneParticipant @lynne]

Neil, Thanks for your response. I am venturing into the unknown on this one. The ordering info chart does not

mean a great deal to me, and thoughts like 'how will I know that the pins will line up withe the holes in the

board' etc etc are cause for concern. That is why I was hoping to find a like for like replacement. I wish I was a

little more clued up on electronics. I have the relay off the board, so I will have a go at determining which pin does

what, and as you say I do know which is the out pin. Regards, Lynne

[RJWParticipant @rjw]

For me, sorting out the non functioning ABS on an Alfa Spider on which the pump won't communicate with test software, then once that's sorted, strip out the original alarm system (no key!) and patch in a replacement Thatcham system ………… separate to the ignition key transponder immobilizer thankfully!

May also be yelling for help from the electronics whiz musicians amongst you later (when my chopped fingers are useable again)!

A chum has given me a superb Technics SX-PR602M piano, everything works, but the sound is distorted and fuzzy, works better on an external amp, but the fuzz is still there, same through headphones, gather it's probably an amp problem?

John.

[Russell EberhardtParticipant @russelleberhardt48058]

Been playing with a Raspberry Pi. I've just managed to get my weather station connected to it and put online using Apache webserver software: **LINK**

It's a powerfull little toy – must think of something more useful to do with it

Russell

[davebParticipant @daveb17630]

Posted by ronan walsh on 06/11/2014 16:01:11:

I was big into electronics as a kid (long time ago now) always working on something, but for some reason i wandered away from this line of interest. Can anyone recommend a project to get me back into the swing ?

It depends on how long ago you were involved in electronics and what you want to make. Electronics now = connect block A to block B and add program. Over the years, integration has taken over and because discrete components are manufactured for bulk users, the trend is to smaller and smaller packaging designed to be assembled by machine. Not impossible to work with but a bit too much like watch making for me, I prefer things I can see with the naked eye. If you have been away from electronics for a few years, prepare to be AMAZED.

[Thomas KaneParticipant @thomaskane35804]

I'm a first year engineering student and I'm part of the formula student team at our university. We're aiming to be the first team from the University of Leicester to compete and race at the Formula student event in June. Our car is electric and as the event approaches we're experiencing a few teething issues, mainly relating to the cooling of batteries (located in the side pods) and packaging of the AIR's (Accumulator Isolation Relays). If anyone can give us any advice on cooling HV electrical components that would be greatly appreciated. Also if your interested you can find more information about the team on our website http://www.uolracing.co.uk and on our crowdfunding **LINK**

[MuzzerParticipant @muzzer]

Not heard them called AIRs before. Most people call them contactors in the EV world. I sort of know, having worked with EVs and HEVs for the last 20 years, but times change!

Generally, if these are air cooled batteries then you need to use fans and ducting. Of course, if they were water cooled, you wouldn't be asking. Sounds as if you need to look into suitable fans and the art of forced air cooling. If you want to dive into CAD simulation, Solidworks has a free CFD module that works quite well. However, you could do worse than getting hold of some decent 12V fans and 3D printing yourself some ducting to channel the air around and away from the battery cells. At least a lot of it is fairly intuitive – if it gets hot, blow some air past it.

Murray

[Anonymous]

Like Murray I've worked on electric and hybrid vehicle packs on and off for over 20 years. I'm currently designing a new BMS and battery pack for a hybrid electric vehicle.

I've always called them contactors too. If the design is right then none of the contactors, isolators, pre-charge relays and the like should need cooling. The exception would be the pre-charge and/or discharge resistors. The power dissipation in these is transitory, so bolting to a metal surface should suffice. But be careful, a lot of power resistors have very poor overload characteristics. As for the batteries Murray is right. I've never seen or designed any packs with anything other than simple forced air cooling. However, you need a decent fan that will work against back pressure. Computer style fans are useless; you really need a centrifugal fan. The trick is to get the air to flow where you want it, over the batteries and nowhere else. It's not that difficult but requires attention to detail as air is pretty fluid (!) and will take the path of least resistance whether you intend it or not.

It would be useful to have an idea of what battery chemistry and volts/amps range you are working with.

Andrew

[Danny M2ZParticipant @dannym2z]

G'day.

As you are racing your car, the design of a low drag cooling system would be worth investigating.

Have a look at this site for some ideas on low drag cooling system principles. **LINK**

I used these principles when re-designing the engine cowling on a racing model and gained an increase of 7% more airspeed with increased engine reliability (less plug changes) due to the improvement in cylinder head cooling.

I realise that you are cooling batteries, but the same principles would apply – the efficient removal of heat with minimum drag increase.

* Danny M *

[Johnboy25Participant @johnboy25]

Jason…. I like the Glen Millar effect! It made me laugh! I can't understand what the obsession is about with valves I learnt my electronics on thermionic devices but still believe semiconductors are just as good. The only thing is that you can read the newspaper by the light from the heaters. 😉

John

Edited By Johnboy25 on 10/05/2015 07:52:47

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