prototype boards

[kevrus]

In case anyone is interested, ive made these boards for various picaxe chips so they just plug into breadboard...makes prototyping a bit easier. Download circuit, reverse polarity diode and decoupling cap included on all boards. I still need tomark the supply pins with appropriate coloured paint.
The 5v psu board is still lacking a board mounted switch and the right angle pins for plugging in, but when fitted it will plug into the psu rails on my breadboard.
The firmware board is designed to solder to a LCD display in piggy back fashion, incorporating contrast control, reset button and jumpers for the welcome message,baud rate etc. It has a 4 inputs on a latching plug system...+5v, grnd, serial in, lcd backlight control. The backlight can be permanently lit by an on-board jumper if control is not required hence only 3 connections are required. I figured it would be easier to have just 1 board for LCD displays instead of trying to incorporate the firmware chip into various project boards.

 

[picaxester]

Cool!

Do the pins ever tear the copper off of the board when moving the circuit from one bread board to another?

 

[kevrus]

no problems as yet, the pins are 'right angle' header connectors which fit through the holes in the pcb as per a normal component and the board mounts vertically into the breadboard.

 

[manuka]

Nice work! Once solder secured these header pins are super robust- I've used zillions & rarely had problems. How about some close up pix , including track side?

 

[leftyretro]

no problems as yet, the pins are 'right angle' header connectors which fit through the holes in the pcb as per a normal component and the board mounts vertically into the breadboard.

That can be a weak point, but your right angle connectors should help. There is a lot of force and flex when repeatable pulling into and out of solderless breadboards. Wouldn't hurt to also run some epoxy glue along the pin to PCB interface.

Lefty

 

[kevrus]

Using epoxy is a good idea, now where's my araldite?
I tried to get some close-ups but couldnt get a clear image so ive taken some pics of the track layouts for the firmware board and the 08/08m board as shown on my monitor...all layouts are shown from the component side.

 

[vk6bgn]

Kevrus,

Nice boards and artwork too. What software program are you using for your circuit board artwork? Are you using that blue "Press & Peel" iron on transfer in conjunction with a laser printer before etching?

 

[kevrus]

I use PCBwizard 3 for the pcb design but i don't use the auto-routing as i've never been 100% happy with the results. I prefer to place the components and route manually, I find its easier to get board sizing and component spacing more too my liking...quite time consuming and it does lead to errors at times though.
For the artwork, I inkjet directly onto 112gsm tracing paper which produces sufficient opaqueness for my homemade UV light box, exposure time approx 5 minutes (mechanical run-back timer used at present so not exactly accurate...I feel another picaxe project coming on!). I've never used the press n peel system, previously used transfers onto acetate for the artwork, now that is painstaking and so frustrating if there's an error.

 

[Andres Rodriguez]

Excellent info and great artwork.
I have used the toner on acetate method with reasonable results (after lots of retouching with a marking pen. Could you tell us more about the ink jet and UV box method?
Particularly about the homemade UV box.

 

[Steve Joblin]

I too would be interested to find out more about the UV method... I don't have a laser printer to do the toner-transfer method, and I am reluctant to buy a laser printer just for a few hobby boards. Is a UV set up less expensive and more accurate than Toner-Transfer?

I've been checking out Yahoo!'s Homebrew PCB forum (http://tech.groups.yahoo.com/group/Homebrew_PCBs/), but it seems most folks use the the Toner Transfer method.

 

[Hooter]

In case anyone is interested, ive made these boards for various picaxe chips so they just plug into breadboard...makes prototyping a bit easier. Download circuit, reverse polarity diode and decoupling cap included on all boards. I still need tomark the supply pins with appropriate coloured paint.
The 5v psu board is still lacking a board mounted switch and the right angle pins for plugging in, but when fitted it will plug into the psu rails on my breadboard.
The firmware board is designed to solder to a LCD display in piggy back fashion, incorporating contrast control, reset button and jumpers for the welcome message,baud rate etc. It has a 4 inputs on a latching plug system...+5v, grnd, serial in, lcd backlight control. The backlight can be permanently lit by an on-board jumper if control is not required hence only 3 connections are required. I figured it would be easier to have just 1 board for LCD displays instead of trying to incorporate the firmware chip into various project boards.

I have just started using the toner transfer paper from Pulsar using the laminator method with excellent results. Check out www.pulsarprofx.com. I am about to import some of the Decal product as well to try making decent panel fronts.

 

[Mycroft2152]

The "blue' film tends to be expensive, there are many other papers that can be used. There has been a lot of success in using clay coated paper from magazines.

There are a few tricks to get perfect boards, clean the pcb thoroughly, use enough heat to fully fuse the toner ot the pcb, and be a little patient when removing the paper/film. A laminator provides consitant and controllable heat and pressure.

Here is an excellent link to the Toner Transfer process:

"PCB's on the Cheap" http://myweb.cableone.net/wheedal/pcb.htm

The process he descibes is almost identical to the one I use. I like to add a "flash fuse" step after removing the paper, using a hair dryer to reheat the toner to level it out and remove any pin holes. Also re-running the pcb though a laminator with the silicone backing sheet from labels also works (similar to using the 'green' film).

The same Toner Transfer process can be used to add the component markings to the top side of the pcb.

For further info on the many different ways of making pcb's at home, take a look at the Homebrew_PCBs group on Yahoo.

http://tech.groups.yahoo.com/group/Homebrew_PCBs/

Myc

 

[kevrus]

Having never tried the toner method, I couldn't comment on accuracy or quality although I have been impressed with photos that i've seen on-line.
My UV light box is homemade from MDF incorporating four 15w 12" fluorescent tubes, an electronic ballast to drive them (only because it's compact and I had one, normal switchstart control gear would suffice), and a nasty mechanical runback timer (soon to be replaced).
Using photo-sensitive coated board and the inkjetted image on 112gsm tracing paper, I am currently exposing for approx 5minutes, (seems to be the minimum time on my timer). I think that this is a bit too long though so will experiment when a new timer is made.
The board is then developed in a weak caustic solution (not ideal) or a proprietary PCB developer (recommended) before etching.
As for cost, I reckon if you can knock up the light box instead of buying one, it should work out quite reasonable.

 

[solderman]

Nice item, the boards look the business.
The UV exposure is somewhat like other photographic processes - a small variation in time/temperature makes relatively little difference. What is important is that the boards are correctly coated (with photo-resist) and they need to be clean.
Even UV "spread" is also an issue, but a mechanical timer is quite good enough. Over time the UV tube will age, resulting is a lower output. If it's 5mins "new" it should rise in a few years' time. By then you'll have updated, in all probability. I understand that "blacklight" UV tubes are not "hard" enough, and great care is needed to avoid "seeing" any radiation, but I'm guessing you're well aware of these issues....worth mentioning though, if others are considering going this route.

 

[kevrus]

Good points about the UV spread and tube deterioration. Some years ago, I made my first UV light box and used 'black UV' tubes with no succss at all. In fact, just leaving the boards in daylight worked better. Further investigation revealed that the UV wavlength from these tubes was incorrect hence the boards didn't expose.

 

[Mycroft2152]

While googling "PICAXE" late Friday night, I can across this "AxeME Picaxe Construction Set".

http://www.qrpme.com/AXE-USER_PDF.pdf

I must admit that iI had a good chuckle over its very clever design and packaging.

I am not invloved with the company, but I was a "Mainer" or "Maniac" living in the state of Maine USA for a number of years. Where else would someone have access to cannng equipment?

Myc

 

[profmason]

PCB construction

I have just spent the last few days making PCBs using the toner transfer method. I needed a small board with a 14M and a ULN2803.
I wrote up the toner transfer process here. (using press and peel blue)
http://profmason.com/?p=472

After the entire process I wrote up the pluses and minus of different prototyping techniques based on my experience as a hobbiest.
http://profmason.com/?p=480

Basically I am returning to using strip boards. I find my productivity is much higher and the result is sufficiently durable to survive in the conditions I expose them to.

have fun!

 

[hippy]

@ profmason : Thanks for sharing. I'm not sure the disadvantages of stripboard are that bad -

Not attractive : Some home made PCB's can look pretty horrible too. Put it in a box and no one will be any the wiser.

Lifting copper strips : Never run into that problem myself. I've cut a few holes where I shouldn't have, de-solder nearbly copper and slip a slither of wire across usually works.

Restricted to one side of the board : So are most home made PCB's.

I think the big advantage of PCB over vero-board / strip-board is for higher-density tracking, high frequency operation and being able to easily use non-0.1" pitched components.

My biggest mistake with strip-board is usually in trying to get it onto a board which is too small. Designing a strip-board layout / component placement is the hard part I find and probably takes longer than for PCB schematic entry and auto-tracking. Cutting the holes in the right places and getting wiring right is a challenge which a PCB doesn't have.

My decision has been to stick with strip-board and only use commercially manufactured PCB's.

 

[Michael 2727]

When using Vero board/Strip Board I have made up blank
boards in Autotrax and place the components for sizing.
Much quicker.

And cutting tracks is fiddly and dangerous, I just use
a 4mm drill and find the closest pad to drill out for the breaks.

 

[Steve Joblin]

Excellent write-up! I am curious as to why you list "Not attractive. The appearance is messier then the PCB because the jumper wires are exposed on the front of the board. " as a disadvantage to stripboard... I usually run all the wiring below, so all you see on top are the components and a few well placed wires.

 

[Mycroft2152]

Vero boards and point to point wiring is OK for simple boards and for one-of designs. Using wire wrap wire (very thin) keeps the appearance clean.

Correcting problems in the rats nest on the back of a hand wired board is a PITA.

BUT, if there is any possiblity of making additional boards, either now or down the road, the pcb process is more efficient.

Also, with the proper pcb program, you first draw the schematic then convert it to the pcb, which reduces the amount of errors.

If you are working with surface mount devices, they are coming, then a pcb is almost a must.

I've done it both ways, and at the present time I can create and etch a pcb in less time time than it takes me to hand wire one.

Just my 2 cents...

 

[hippy]

Good points about the time it takes wiring up a strip-board ( and checking it's right ) plus the ease of duplicating PCB's.

 

[kevrus]

Well, as I mentioned earlier in this thread, i've now made a picaxe/lcd display timer for my UV light box and can report that I had good results with an exposure time of 120 seconds. Each time i'll reduce by a few secs to see what the minimum time is.
So thats the board etched for my next project which is an outside temp monitor and two zone frost stat, for my zoned CH system, with one user adjustable setting (for both channels individually) and three preset settings.