Is this feasible ?

M

manie

Senior Member
My latest effort for a 4 digit 7-segment display. It requires 4x CD4026B's plus the 08M and connectors. I've made it bigger (100x160mm Eurocard size). It is a double sided layout BUT (again..):

1 I've never worked with double sided board before
2 I'm quite happy to do a single sided board even with 0.5mm tracks. Done a few of those before on pre-sensitised board which works very well for me.
(I have a good 120W UV lamp, 8-10min exposures, NaOH developer (Yugghh), and HCl/Peroxide etchant.).
3 The question of feasibility is this:
3.1 Can I do it using TWO normal boards sandwhiched together, one as bottom side and the other as top side with "pins" inter-connecting them both (all holes) ??
3.2 Should I rather get some pre-sensitised double sided board (NOT AVAILABLE LOCALLY, not even single sided) and do it that way.
3.3 If the recommendation is 3.2 above, how do you expose both sides to UV light so that all holes LINE UP ??
4 The second question is:
4.1 Should I rather get an LCD display (easier I think) and use that ?
4.2 If recommended that 4.1 is best, which LCD (2x16 or 2x20 etc) and does one need the firmware or is the firmware just a better route to go ?
4.3 If the Rev-Ed LCD is pricey (ZAR vs Sterling exchange) will something from Futurelec work (they're quite a bit cheaper...)

Once again your input/recommendation/scolding is appreciated. This old-timer is learning a lot lately !!

PS: A jpg of the INTENDED double sided layout is attached. 4 digits is NOT EASY !
Edit: Minimum trace width is 0.75mm in some places, 1mm in others, and I will go as wide as possible where ever I can. I will also do a copper pour connecting to the 0V net....

Here is a link to a local supplier with displays at good prices (compared to exchange rate prices). Please let me know what you think..

Manie
 

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D

Dippy

Moderator
"3.1 Can I do it using TWO normal boards sandwhiched together, one as bottom side and the other as top side with "pins" inter-connecting them both (all holes) ??
3.2 Should I rather get some pre-sensitised double sided board... "

I don't know what you mean as 'normal' board (to me, presensitised IS normal).

But, in the past I have done D/sided as 2 s/sided stuck back to back.
This does have the advantage that lining-up holes at the UV stage isn't important.
However, be aware that some legs aren't quite long enough to go through double thickness e.g. some IC sockets. In this case you may have to get 'wire-wrap' IC sockets - thats merely an example.

For double sided board there are a few ways.
1. Make registration marks or holes in the board.
2. Pre-cut the PCB to exactly the right size to match your artwork profile, so then you can line up the board. Mark a reference corner so you get it right way round.
3. Print the top and bottom artworks onto transparency. Then line up the transparencies and staple them a cm or so out from the profile line. You now have a 'pocket' into which you can slide the PCB.
Ideally done in a pukka UV box so that no UV slips round the corners.
Remember to print one side mirrored so that the toner side is in contact with the photo resist.

Remember with some IC sockets (and other things) you can't get a soldering top-side so you may have to make an extra via or make a top-bottom connection elsewhere.
I see that you've done this - It's a note for others.

All of the above is for photo-etching. I have no experience of iron on stuff.

LCD vs LED?
Which do you like?
LEDs won't be nice in bright sunshine. But LCDs have squitty sized characters - unless you get fancy.
'Easier' is difficult to say.
If you are planning to use a serial LCD then just a few wires and a piece of cake.
Or if using a 'normal' LCD then there are more wires and code - though the code is available all over the shop.

PS. Where is the link?
 
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manie

Senior Member
D:
"normal" is "single sided", obviously as I said, pre-sensitized.
Can you elaborate on "wire-wrap" IC sockets ?
As for LCD, prefer good'ol RS232 if I can skip a lot of wires etc, the board stays neater that way. After my experience now, trying to get a MERE 4 digit display going, I think I'll stick with serial LCD maybe. Code a bit more involved probably but other benefits, eg. No sticking boards back to back...
Remember with some IC sockets (and other things) you can't get a soldering top-side so you may have to make an extra via or make a top-bottom connection elsewhere.
Click to expand...
I don't quite understand what you're saying here ??

Seems I missed the link. Here it is:
http://shop.rabtron.co.za/catalog/index.php?cPath=41_165
Edit:
Attached is the .pdf for one LcD at the above site:

Manie
 

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springer

New Member
have yu thought of this!

i know your almost at the 'lets build it stage' but have you considered using 7-seg bcd displays. its an integrated LED 7 segment hex display and logic, and doesn't require any of those nasty resistors.

date sheet here... http://www.rigpix.com/components/til311.pdf

i use this type of display all the time when i need to save space and component count. cheaper too when you consider the support chips.

Just my 2p worth....
 
M

manie

Senior Member
manuka said:
Manie- never mind THIS quest- how HAS the wireless chook house project worked out??
Click to expand...
Stan: THIS is the temperature sett/display module for exactly THAT. The RF side I havent looked at yet but think I will soon just using 28x1 project board and PC etc. Sorry to disappoint you, will report back...
Manie
 
M

manie

Senior Member
Springer:
i know your almost at the 'lets build it stage' but have you considered using 7-seg bcd displays
Click to expand...
I'm no where NEAR that feeling !! MUST be an easier way, your suggestion might just work here, pity that it uses up 4 pins for each digit, or is there yet another surprise solution to that problem ??

Thanks for the "Heads-up", I'm considering it already...
Manie
 
M

manuka

Senior Member
Manie- you are NOT disapointing me, but rather setting yoursef up for frustration. I say yet again that you should run a "proof of concept" wireless data test FIRST. It's otherwise akin to to assuming the likes of a new plane design will fly, & spending time (that should have been spent on the structure) designing the cabin instruments & seating fabrics etc! It it doesn't fly these are pretty incidental!

In fact flight is a near ideal analogy, as the key to the Wright Brother's 1903 flight success was that their engineering went way beyond the assumptions & "of couse it'll work" methods of their contemporaries. They evaluated flight physics & aerofoils at first principles, using a series of scientific experiments that culminated in their famous wind tunnel.

This is the last I'll say on the wireless matter... Stan

EXTRA: I'd say LCDs too, but such boring issues as reading in a dim room may arise in your case.
 
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kevrus

New Member
Can you elaborate on "wire-wrap" IC sockets ?
Click to expand...
These ic sockets have much longer legs...approx 1/2inch long (12.5mm for the metric guys)
so they will easily go through two boards sandwiched together.
Some ic sockets like some of the wirewrap sockets and also turned pin (I believe they are called) actually sit slightly proud of the board so it is possible to solder the pins on both sides. Need a small 'bit' in the iron though
 
K

KIGX

Member
Manie,

My vote is for the LCD. I used a 3 digit 7-segment display driven by 3 4026s and it works quite well. The down side is that you need to pulse the display to the desired number and the display visibly scrolls while it is doing it. It's not too annoying, using pulsout it goes quite fast but the more digits you have the longer it will take. Better yet is to use another PIC pin and pulse the reset on the counter to reset it to zero. That way you will see less scrolling but use another pin. You could use yet another pin and blank out the display while it is scrolling but... The BCD option mentioned earlier would be better since you can go directly to the number you want. It will use 4 pins but that's only 2 more than the reasonable option for the 4026s and I suspect that you could in fact do it with one pin and a serial to parallel converter and a bunch of code.

The LCD is much more flexible in terms of what you can display and how you display it. I'm now using a 20X4 LCD serial display. I have the Wulfden K107 driver board driven by a phanderson #118 chip. The wulfden kit was about US$34 and supplied the PCB, parts, phanderson chip, LCD, and cable to hook to the PIC. Basically it is plug and play after a little soldering. Note that the PICaxes use the phanderson #118 at 2400 baud and that's what you would order from wulfden if you go that route.

Small squiggly numbers was mentioned earlier. I go the blue background with white letters display and I think it is just great. The backlight really shows the numbers etc, up well. There's also a big number feature with the phanderson chip but I haven't used it - see his web site.

http://www.phanderson.com/lcd106/lcd108.html
http://www.wulfden.org/TheShoppe/k107/about.shtml

After reading the documents on the wulfden and phanderson sites I had the LCD printing out what I wanted in short order.

Why use the LCD? Once you have the wireless link to your chook house you might want to monitor the link to see how many transmissions are being received and how many are being 'missed' due to corrupted data. Easy to display along with the temp on an LCD. What about other amusing things to from your link or for display? Battery level monitor, wind direction, wind speed, relative humidity, the high for the day, the low for the day? The LCD would be a few bucks more than the 7-segments but a lot less work and a lot more flexible option.
 
M

manie

Senior Member
Stan:
This is the last I'll say on the matter... Stan
Click to expand...
I'm sure its not.... promise me its not, who else will take up the slack to keep my wandering mind a little focussed ? I was promissed 300 meters LOS, if it does'nt meet that, they said they will exchange for something more powerfull. We'll cross THAT bridge....

KIGX:
At present I'm seriously considering the LCD option, serial off course. And yeah, I've planned to include PC based database software to do all the max's/min's/aver's/charts and graphical weather data etc. Thanks for the response...

Kevrus:
Then I knew what they LOOKED like but not what they were called. Thanks for that, its the one thing still keeping me from going "sandwhiched" double sided. Getting some of those components locally might be near impossible, NOBODY carries decent stock levels and variety anymore and blame it on something called "inflation".
Manie
 
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Dippy

Moderator
Sorry,
I didn't realise that normal was s/sided with photoresist.
'Normal' to some people is a bit of stripboard.

And , sorry, I'm probably making yet another ghastly error.
You said: "...prefer good'ol RS232 if I can skip a lot of wires etc"
- but your link shows 'yer average' (normal?) 4/8bit LCD parallel type.
Will you be using that in conjunction with a serial LCD firmware chip?
Please feel free to use the word 'obviously' ;)

"wire-wrap" - as Kevrus says.
-it was merely a suggestion if you ran into thickness problems with 2 x 'normal' PCBs.
If thickness isn't a problem then take his advice re turned pin sockets.
They usually cost a few pennies more.
 
M

manie

Senior Member
Dippy: "obviously" was used from my perspective, I will not use spray-on resists on blank (non sensitised) boards. As to the link, yes I would hook up via the firmware to get the ease of serial comms, its worth the money to save time instead floundering about with traces and/or wires. I'm sorry if you misread "obviously", here we use it as in Yankee "I guess so..." or "naturally. No offence was meant.

Eclectic:
Where did you find them ? Never even saw them on a "Google SA web pages" search. Yes, I could use them, some items seems a bit pricy, but considering shipping cost and import duties I think they are probably in line with overseas prices. They certainly seem to have a big variety of usefull stuff other than the same old goodies offered. Their "wire wrap" section is stocked well it seems. Finding good thin and soft "panel" wire is quite a job here, and they have a choice of COLOURS ! Man thats good to know. Thanks for the tip mate...
Manie
 
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