"Gym Bean" SMD Timer

Dicky Mint

Senior Member
Hi All

I am building a "Gym Bean" (my name) for my business consultant and as part of a possible run of "Gym Beans" as kits for interested parties!

I have soldered together a prototype as carefully as my hands and eyes will allow but I can't seem to download a program to it?

When I try and download a program I get the generic respose of "hardware not found on COM3"!

This all reminds me of my first steps in picaxe a fair few years ago!

my PCB design is a little unusual for one with a reasonable experience of this forum but hey to make an omlette you have to break an egg or so?

so putting my first foot (in it) first... It doesn't have a conventional CON039 download socket!

(I can hear you tutting before I even finish my discription!)

But because it is not designed to be reprogrammed it has a simplified 3-pin female pin header.

I can use this interface to programm the SMD PICAXE in dire need or in the case of the prototype, repeatedly.

I am aware that this breaks a golden rule but I've broken another...

I've run tracks between the pads of 1206, SMD, resistors and capacitors; two in places!

I am after some insights concerning fault finding of SMD designs from those that are in the know

Kind Regards

Rickz

Here are my PCB design and the cct dias I'm working from.Capture of cct dia.JPGCapture of PCB.JPG
 

Dicky Mint

Senior Member
Hi All

Thanks Tex for the reminder about the 'hard reset' proceedure. Unfortunately I've tried that and it doesn't seem to work!

I'm normally keeping my finger on the button to connect power to the PICAXE

I've checked the COM port out and I'm correctly on COM3.

Sorry Al but I'm afraid that won't help as I'm absolutely certain that the connections to the PICAXE are correct!

"Famous last words" I hear resounding in my ears!

I've taken some pictures but unfortunately they're out of focus

the PCB layout diagram shows the main features of the PCB though

There is some life though:- it draws 3.2 milliamps when the button is pressed.

There is 0.5 volts accross the PICAXE power pins when the button is not pressed

and 3.2 volts from the supply

When the button is pressed the potential accross the power pins increases to 3.13 volts

I think therefore that there is not a problem with the transistor auto-off part of the circuit?

so the problem must be in the download side of the circuit?

Any ideas welcome

Rickz
 

Dicky Mint

Senior Member
Thanks Steve

Yes to no avail i.e. the port is good

I've also tried the 'loop test' to no avail i.e. it works flawlessly!

I'm just looking at a board I etched yesterday and there is a small, but significant, error!

There is a "gap" about a millimeter long in one of the traces under a PICAXE08M2 going to the download circuit!

If this is a visable problem then perhaps there is a similar 'break' in a trace on the Gym Beab PCB maybe not so visable?

I think I either might try another from the same batch of Gym Bean PCBs I made a few days ago.

Or even get a few made up professionally?

Rickz
 

MartinM57

Moderator
I would suggest you check the (every?) PCB for connectivity where it is needed and no connectivity where there shouldn't be any, before fitting any components.

If you're home making PCBs with two traces between the pads of 1206 components pads, you're better than I would trust a (low-cost i.e. Chinese) professional/commercial fabricator.

I haven't looked in detail, but it should be possible to layout the board without having that manufacturing challenge. If you're limited to single sided, link wires may be preferable to running traces between components.

Although it sometimes doesn't look that pretty initially, I sometimes lay out the components on the board in the same orientation as on the schematic - the connectivity is usually then pretty easy (and using say Diptrace for both, you can check in the PCB editor that the board represents the schematic, do design rule checks etc) ...
..and then when you've got the connectivity right you can move the components around, dragging their traces with them, to make a more pleasing/practical layout.
 

Dicky Mint

Senior Member
Thanks Martin

you're right of course I should really test every track for continuity and isolation from the begining!

I'm spose I'm used to just giving them a physical check when they come out of the etching solution!

Your idea of getting them done professionally is one I'm currently investigating OSHPARK in US seems to be my favourite ATM as they are very reasoably priced and, so far perfectly reasonable electrically!

I must admit I don't check their PCBs as thougherly as I should my home brew and take them to be the real standard in quality!

Beacause of the solder mask between SMD pads I am quite happy to leave the tricky bits in and keep the 'simpler' idea of two tracks through a 1206 component!

I could re-route the whole PCB actually, as they do double sided as standard, and use both sides of the PCB to route tracks instead of having them through SMD pads.

The factor here is cost. For a run of 3 for prototype work there isn't really a problem, but for a production run that may end up being multiple boards the possible price of around £2 or more per board could be prohibitive?

The blatant 'gap' in the trace of another board underminds my confidence in my own ability and in the PCB fabric itself!

Rickz
 

MartinM57

Moderator
Production run?

50 off 34mm x 30mm double sided from Itead is about $60 to your UK door by DHL, about 9 days from placing the order/submitting the Gerber files. 100 off is $77 :)

So between about 50p and £1 each....but only you can say if it's prohibitive or not.
 

PhilHornby

Senior Member
50 off 34mm x 30mm double sided from Itead is about $60 to your UK door by DHL, about 9 days from placing the order/submitting the Gerber files. 100 off is $77 :)
http://www.allpcb.com quote is $21 via TNT/DHL for same thing.

See my 'review' of AllPCB.com, here: http://www.picaxeforum.co.uk/showthread.php?28717-Single-sided-PCB-manufacturing&p=316201&viewfull=1#post316201

(Note: AllPCB.com will reward users for posting favourable reviews in forums. Rest assured, I have not told them about mine and have not claimed any reward.)
 

Dicky Mint

Senior Member
Thanks Martin

Even at $77 per hundred they're better value than I'm quoted.

Thanks Phil,

I'll look into that!

Is the cost really $21 to my door for 50 pieces?

Rickz
 

Dicky Mint

Senior Member
Right I've got another two boards not downloading a program

I'm therefore thinking my problem is in the downloading of the program, software?

I'm thinking of uninstalling then reinstalling the drivers.

Is that a good idea?

Rickz
 

MartinM57

Moderator
I'm therefore thinking my problem is in the downloading of the program, software?
..and you've checked continuity and insulation? I know it's boring, but...

OT:having just received 100 12.4cm circular white PCBs from Itead, I see an AllPCB quote is about 60% of the price :) :( There's a note on the Itead site about TNT (vs DHL) when you get into the ordering process about TNT charging $25 or so for collecting the duty/VAT
 

Dicky Mint

Senior Member
Hi Martin

I've been a bit distracted unfortuneately so haven't done the continuity checks!

I'll get too in soon!

OT: I've just ordered 50 of my redesigned two layer boards with allPCB for the princely sum of $21 including postage and vat.

Regards

Rick
 

Dicky Mint

Senior Member
well I've done the continuity checks and it all checks out.

Progress though with the other board that previously refused to download a prgram, it has started to work properly!

This is great but unfortuneately my Gym Bean is still not working!

I'm sure its something simple I just can't seem to find it?

Rickz
 

Dicky Mint

Senior Member
well the other board loads the exact same program flawlessly!

It's a test and pre-programming board for Gym Bean, SMD, PICAXEs.

It could be an intermittant fault where the pressure of the multimeter probes is causeing a hairline crack to read as continuity when there isn't any?

I'm a bit at the end of my tether. I can't think of what might be the trouble?

Rickz
 

Dicky Mint

Senior Member
well I've performed "brain Surgery" and swapped the 'blank', SMD, PICAXE08M2 for an SMD PICAXE08M2, which I programmed in my SMD programmer; and, guess what, The Gym Bean works flawlessly!

A bit of tweaking and I should be ready to go!

Never did find out why the download part of the circuit didn't seem to work?

I'm pretty sure my design is ok!

Thanks for all your input

See you again

Kind Regards

Rick
 

PhilHornby

Senior Member
There's a note on the Itead site about TNT (vs DHL) when you get into the ordering process about TNT charging $25 or so for collecting the duty/VAT
Paying the duty is a nightmare - paying what you owe in tax is one thing, but paying someone an arm and a leg to collect it, is quite another. DHL appear to quote 2.5%, with a minimum of £11. I can't remember Royal Mail's figure - but think it's about the same. AllPCB.com helpfully lied about the value of my order and my last purchase from Itead, was apparently a 'gift' :eek:.

The DHL website says
Some businesses have their own Deferment accounts with HM Revenue & Customs and we merely arrange for their account to be directly debited by Customs
I wonder how you set up such an account ?
 

MartinM57

Moderator
Never did find out why the download part of the circuit didn't seem to work?
The schematic and the PCB are inconsistent - on the left, pin1 (PICAXE supply +) goes to T1, on the right, pin1 goes to +3v, C1 and C2. The board only has pin1 going to T1, C1 and C2 - no connection to +3v. (and the PCB has a 0R resistor, presumably for routing, not on the schematic - it's recommended to use a schematic/PCB design program that will spot inconsistencies like that (Diptrace, cough, cough))

So with a brand new unprogrammed PICAXE that's got pin6 as an open circuit, what's the voltage on pin1 (via DMM measurement) when you're trying to program it?
 

Dicky Mint

Senior Member
Hi Martin

you are quite correct and it's unintentional.

The cct dia should show, on the right, that pin 1 goes to the capacitors and by default pin 1 of the PICAXE, instead of the supply.

Yes the zero ohm resistor is for routing purposes.

I'll take a look at diptrace but I'm very fond of the old program 'Sprint Layout' and have been using it for years, quite happily I must add!

That value for the virgin PICAXE is around 3 volts.

I measured it earlier but didn't write it down. As ATM I've got a programmed PICAXE in the prototype.

Hi Tex

Perhaps you'd like to see a photo of the SMD, PICAXE08M2 programmer?

My computer is not responding ATM so no pics just yet!

Regards

Rickz
 

techElder

Well-known member
So, I'm taking it that when you say, "SMD programmer" then you are identifying a hardware holding fixture for the SMD package.

When I read that, I was concerned that you had changed the programming method you were using and caused a problem.

However, when you get time and situated, I'd certainly like to see how you do things.
 

Dicky Mint

Senior Member
Hi Tex

I've got my computer up and running again or limping would be a more discriptive word!

I'm not able to load my computer with photos from my iPhone for reasons I can't for the life of me fathom but I've emailed myself one and it should transfer from there?

I designed the SMD PICAXE08M2 programmer and tester so I could preload a program on an SMD PICAXE!

Its made up of a SMD SOT-08 sprung loaded clamp and converts this to DIL factor.

the board then has LEDs to test the outputs and potentially a switch to test the C.3 pin.

It is powered by a CR2032 3V lithium cell.

I did change the programming method but it was from one that didn't work to the SMD programmer which did!

Kind Regards

Rickzthumbnail of SMD programmer.jpg
 

MartinM57

Moderator
For the main board, can you temporarily hook up some LEDs and resistors between:
- Serin and ground
- Serout and ground
...do they both flash when programming?

Your programming board looks like it uses a AXE027 cable into the jack socket - how are you getting the AXE027 to the Gym Bean board - via a jack socket and wires to a 3 pin connector? At the back end of the jack socket there are two pins for each connection - have you joined them together...I can't remember which way round it is, but if you just use the outer pins/just use the inner pins, one way works and one way doesn't :)
 

Dicky Mint

Senior Member
Ok Tex

I thought it was pretty cool too! Even if it was my idea?

Martin

I always join them together and most often they work fine.

The CON039 socket has 5-connections shown in the datasheet, two are, if I remember rightly, normally closed until the plug is connected.

That would echo your observation! If the normally closed terminals were conected to your board they would provide an open circuit as soon as a jack plug was inserted.

I can't seem to be able to download the datasheet ATM but, from the notes I've read, this is the situation!

I've tried connectng LEDs to the PICAXE Serial Out and Serial In on my SMD programming/evaluation board. The LED connected to serial out flickers as the chip is programming. As it should.

I tried connecting an LED to the Serial In but it prevented the system from downloading a program. I guessed It would be as you figured, a useful tool, but unfortunatey, it loads the input only pin and seems to leave the whole thing unable to download!

When I disconnected it, the board began to work flawlessly! i.e. the program downloaded!

Where I'm at now is; I have redesigned, from scratch, the Gym Bean PCB to include circuit updates and other developments.

I am leaving it to lie 'fallow' for a day or so so any errors get a chance to come to light.

I'm also going to attach some snips of the Brand New Gym Bean PCB layout and the circuit diagram for your perusal!

Thanks for all your input.

Regards

RickzCapture of Brand New Gym Bean cct dia 01.JPGCapture of Brand New Gym Bean PCB 01.JPG
 
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