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What Electronic Projects are you working On

Seed thread to start things off.

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Neil Wyatt10/06/2014 19:26:06
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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

Muzzer11/06/2014 02:21:03
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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

Andrew Johnston11/06/2014 11:24:18
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5726 forum posts
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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 211/06/2014 12:26:22
16 forum posts

" 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 udall11/06/2014 12:46:45
2028 forum posts
41 photos
...^... glen millar effect?
Gordon W11/06/2014 13:51:22
2011 forum posts

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

Lynne06/11/2014 13:25:12
83 forum posts
27 photos

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 Wyatt06/11/2014 13:53:24
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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 walsh06/11/2014 16:01:11
544 forum posts
32 photos

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 W06/11/2014 16:11:42
2011 forum posts

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.

Lynne08/11/2014 09:20:34
83 forum posts
27 photos

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

RJW08/11/2014 13:40:03
342 forum posts
36 photos

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 Eberhardt08/11/2014 16:21:33
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2600 forum posts
85 photos

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 itsmiley

Russell

daveb08/11/2014 18:15:43
624 forum posts
10 photos
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 Kane09/05/2015 15:49:33
1 forum posts

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 www.uolracing.co.uk and on our crowdfunding **LINK**

Muzzer09/05/2015 17:01:46
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2904 forum posts
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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

Andrew Johnston09/05/2015 17:14:52
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5726 forum posts
660 photos

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 M2Z10/05/2015 02:30:04
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892 forum posts
283 photos

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 *

Johnboy2510/05/2015 07:51:41
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259 forum posts
3 photos

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

Michael Gilligan10/05/2015 08:42:17
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16637 forum posts
724 photos
Posted by Johnboy25 on 10/05/2015 07:51:41:

... 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.

.

It's the behaviour in over-drive conditions ... Valves produce mostly even harmonics when over-driven, and the distortion is therefore inoffensive [and may improve the perceived sound].

Despite the many attempts at producing 'soft clipping' in semiconductor circuits: Over-driven semiconductors produce all the harmonics and tend to a square wave output ... this is offensive to the ears, and damaging to equipment. [e.g. many a blown tweeter]

MichaelG.

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