Digital oscilloscope project/kit

[John Rudd]

When it comes to soldering the ic to the board......Do Not be tempted to solder all the pins on one side one after another......

If its a qfp (quad flat pack, bit like mfi furniture..... )  solder the 4 corner pins first to secure to the board nice and level.....Then solder alternate pins on each side.....This will prevent the chip from overheating...if you are a bit overzealous with the solder, use solder wick to draw off the excess solder...dont use a solder sucker....risk of damage to chip or pcb.....

[wheeltapper]

No, I've got a 5"magnifier lamp with a shedload of LED's round the edge.
It makes a hell of a difference, those 0805's looked like house bricks.

I think if I ever had to solder 0603's again I need a smaller chisel tip for the iron. the smallest one I have is 2.4mm and I could get a 1.2 or a 0.8.

Roy.

[Bluechip]

I would suggest the 0.8mm tip. That's what I have on my Weller. Even that seems too big sometimes and I don't even do SMT.

Dave

[wheeltapper]

Hi Dave,
I've just ordered a 1.2 and a 0.8 straight after my last post.

the IC lands on the practice board are only 0.8 so anything bigger is going to be too big.

Roy.

[Bluechip]

Here you are, Rob ...

PCB for your PSU, not including diodes & LEDs ..

Done on ExpressPCB. Took about an hour.

Dave

[RobWilson]

Morning and a happy new year to you  Dave   


You missed off my transformer lol , Your layout looks allot more efficient / better than mine  , I like the way you laid  out the  regulators .


All the best , Rob   

[John Rudd]

Happy new year all....... 

Nicely done Dave...

Rob, the tranny connections are at the lhs side of the board..... To the left of the bridge...

If I were building it, I'd use a Molex 3 pin plug on the transformer leads, and use a matching 3 pin header on the board...a much neater approach rather than direct wiring but to each his own....

[Bluechip]

And a Happy and Prosperous New Year to you Gents ... 

If I were doing it, I'd use a PCB mounting transformer ...     like this:

http://cpc.farnell.com/camdenboss/ctfp6-12/transformer-6va-2x-12v/dp/TF01362

but as we seem to be stuck with a snivelling bit of a 3VA Chassis transformer I decided to make the rest of it look a bit Neolithic to suit ...   

A bit nippy here ..    not going out today  .... no sireeeeee 

Dave

[RobWilson]

Rob, the tranny connections are at the lhs side of the board..... To the left of the bridge...

Morning and all the best  John , I did see the connector for the transformer  ,  I want my massive 3VA on the board   

If I were doing it, I'd use a PCB mounting transformer ...     like this:

http://cpc.farnell.com/camdenboss/ctfp6-12/transformer-6va-2x-12v/dp/TF01362

but as we seem to be stuck with a snivelling bit of a 3VA Chassis transformer I decided to make the rest of it look a bit Neolithic to suit ...   



Dave

Hi dave , whats my poor wee transformer ever done to you 

http://www.rapidonline.com/Electrical-Power/Blore-Bowron-A5004-PCB-Transformer-115V-115V-3VA-12V-12V-88-5350    , 




Rob

[Bluechip]

So, not a chassis transformer ???

Oh well, another wrong idea I've got.       I blame Global Warming. I was OK until that kicked in ... must have addled my brain 

I've made templates for the CPC trannies .

So it would be quite possible to mount it on the board.

Dave

[wheeltapper]

Hi, just a quick pic of my test board.


it's not too bad, at least the LED works.

Roy.

[John Rudd]

Rob,
ESR do a line in pcb trannies.......but I guess you aleeady knew that.....

They aint to far from you either at Cullercoats....( boy I love going to that place....lots of luverly conponents.... )

Roy,
Looks pretty good....( for a beginner.... ) for a first attempt....

I have to admit when I'm reworking a board, the thinnest solder I have is .8 mm and I think thats too big...I ought to buy some paste really, but I'm a tight Yorkshireman...you know...

[wheeltapper]

Thanks John.
It is the first time I've used SMD's, I used 0.8mm on the 0603's and 0.7mm on the rest.

Considering that when I look at the board without my glasses I can't even see the damn components I'm quite pleased.

Roy.

[RobWilson]

So, not a chassis transformer ???

Oh well, another wrong idea I've got.       I blame Global Warming. I was OK until that kicked in ... must have addled my brain 

I've made templates for the CPC trannies .

So it would be quite possible to mount it on the board.

Dave

Nope PCB mounted Dave as I shown  about 5 back .





Rob

[RobWilson]

Looking good Roy 


Looks like you will have no problems doing the SMD on the oscilloscope board .




All the best Rob

[RobWilson]

Rob,
ESR do a line in pcb trannies.......but I guess you aleeady knew that.....

They aint to far from you either at Cullercoats....( boy I love going to that place....lots of luverly conponents.... )

I keep forgetting about ESR John  , they are only a few miles away .


Rob

[Bluechip]

Here you are, Rob.

PCB Tranny now in. Looks a bit messy   

Back to my Becks & cashews .. 

Hope I've got 'em re-sized properly.

Dave

EDIT1   Near enuff ... 
EDIT2   Each dot is on a 0.1" pitch

[RobWilson]

Lookin good Dave 


My electronics /PCB software can't do a ground plane   


I could not agree more ,,,,,,,,,,,,where be my beer 


Cheers Rob

[John Rudd]

Dave,
I know you done well......

But I think the distances between the copper infill are a bit close around the transformer....

I prefer at least 6mm creepage distance for safety...

Just  my 2 cents....while drinking my Carling cider....     Enjoy....

[philf]

My electronics /PCB software can't do a ground plane   

Rob,

Are you sure?

I managed to do a copper pour to fill. What i couldn't do was neatly connect a pad to the plane. I've uninstalled it now so can't tell you exactly how to do it.

 

Phil.

[RobWilson]

My electronics /PCB software can't do a ground plane   

Rob,

Are you sure?

I managed to do a copper pour to fill. What i couldn't do was neatly connect a pad to the plane. I've uninstalled it now so can't tell you exactly how to do it.

 

Phil.

Hi Phil

I think I am driving it correctly , I added the copper fill but I cant connect to it  ,  I thought just add the copper fill ,then remove/delete  all the traces that are at 0 volts , but it just isolates the pads .


how did you get a connection ? 


Cheers Rob 

[philf]

My electronics /PCB software can't do a ground plane   

Rob,

Are you sure?

I managed to do a copper pour to fill. What i couldn't do was neatly connect a pad to the plane. I've uninstalled it now so can't tell you exactly how to do it.

 

Phil.

Hi Phil

I think I am driving it correctly , I added the copper fill but I cant connect to it  ,  I thought just add the copper fill ,then remove/delete  all the traces that are at 0 volts , but it just isolates the pads .


how did you get a connection ? 


Cheers Rob 

Rob,

You have to draw a track from the pad to the filled area. (I found somewhere in the help that told me that was the only way.)

I found this in one of their tutorials which shows the filled area but no connections to any pads.



I don't know if you can get sufficient clearance for the pads for your transformer or whether you're stuck with a standard clearance. There will be a way round it I'm sure.

Other software allows you to specify on the pad properties if it's isolated or not.

In my PCB I used one plane for 0v to connect to my Pi and one plane for the 0v from my proximity sensor inputs. I wanted to keep both sides completely separate to keep the 24v away from the Pi which is limited to 3.3v on the inputs.

 

Phil.

[Bluechip]

Dave,

But I think the distances between the copper infill are a bit close around the transformer....

I prefer at least 6mm creepage distance for safety...

Yes, quite right, there should be more clearance.

Did it when I was sober, [ or very nearly ], brain would be lacking some essential toxin and thus not on top form.

Rectified now. Back on full power, like a re-gunned CRT.

Dave

[modeng200023]

I have been following this topic with much interest.

Rob and John or anyone else with experience of using this scope, after using it for a while do you have any reservations bearing in mind that it is resonably priced?

The other thing I'd like ideas on is a case for it if anyone has thought about ready made ones.

John

[RobWilson]

I have been following this topic with much interest.

Rob and John or anyone else with experience of using this scope, after using it for a while do you have any reservations bearing in mind that it is resonably priced?

The other thing I'd like ideas on is a case for it if anyone has thought about ready made ones.

John

Hi John

    £15 delivered its a cracking bit of fun ,it has  nowhere near  the capabilities of a good or even low end bench DSO ,but  for £15 I really can't find fault .

It has also generated a good bit crack on the forum and lead to other topics like a 3DP case , so if you could CAD model a case maybe someone could print one for it ,  I may stick mine in an ally

case , I bought longer bush buttons that come level with the screen , I just need to find away to bring the slide switches forward .


or there is this kits .

http://www.banggood.com/DSO068-DIY-Oscilloscope-Kit-With-Digital-Storage-Frequency-Meter-ATmega64-AVR-Microcontrol-p-981017.html


More than double the price ,but it has a case .


Maybe the more experienced chaps could chip in with some oscilloscope advice 



Cheers Rob