μWatch

[Leviset]

I’d tagged this on the end of the multi~Calculator kit, but I think it needs to be a new post:-
I’ve already told you all BUT “I’m totally useless on the electronics side but good on the Pure Mathematics and Algorithm issues’
I bought a half-completed μWatch Calculator kit. I know it started in 2007 and now I can’t find anyone to help.
I did manage to get the setup instructions coming up on the screen BUT when I folded over the ribbon cable so that the 2 parts could be bolted together to form the watch the red +ve wire from the battery came off from the PCB. I got a friend to re-solder the wire back on, which he did very professionally. However I then couldn’t get the screen to work all. Then the ribbon cable from the PCB to the LCD came away at the LCD connector. It was covered in some black goo which when I cleaned it off the 16 metal connectors were exposed showing on the LCD board. I’m not sure if these are the broken off terminals from ribbon cable, now stuck to the LCD board? (Some pictures attached below).
(1) Does anyone know and can tell me the exact LCD screen I need and would that replacement come with a 16 pin cable already attached to it please?
(2) I bought from Amazon a “MakerHawk 2pcs I2C OLED Display Module 0.91 Inch I2C SSD1306 OLED Display Module Blue I2C OLED Screen Driver DC 3.3V~5V for Arduino” as it looked the right component, but for the life of me I can’t see anywhere where you could attach a ribbon cable?
Any help would be greatly appreciated
Dennis
Sorry it won’t let me attach the images, exceeds available space.

[BobVA]

I think there's a couple of folks here with them, but have you tried asking on Dave Jones's forum? They might be more familiar with it.

http://www.eevblog.com/forum/

[Leviset]

Yes - he said it was a project from 2007 and couldn’t remember the spec of the screen.

[Robert VM]

You probably know about this... just in case.
The µwatch website in step 3: Attaching the LCD shows some photographs of the display ribbon cable without the black goo.
You friend may perhaps also resolder the ribbon cable to the LCD PCB.
Good luck!

[Leviset]

As I’ve already told everyone - I’ve managed to knacker the screen of the μWatch - a combination of 70 year old hands riddled with Rheumatoid Arthritis and poor EE Skills.
I’ve been trying to find a replacement screen but nobody (including David Jones the original maker of the kit) seems to able to help me.
It’s ribbon cable has broken away from the actual LCD where it was connected - there are 16 silver pins left on the LCD PCB - are they from the old cable and been left behind and do I need to remove them before I try out the new 16 pin ribbon cable I have?
I can’t find an equivalent LCD preferably with the ribbon cable already attached - it broke away from underneath the black gunk that was covering the connection.


Do you know (or anyone who does) where I (a) could get a replacement LCD (b) An alternative screen with a better 16 pin connector (c) a way to solve it by say mounting a screen on a breadboard or similar and connecting the rest of the watch to it as I’m not going to try and put it all together as a watch as that’s how I broke it in the first place?
Any help at all would be greatly appreciated - I’ve spent hours online at electronics forums and our own HPmuseum forum trying to find a solution.

[mpark]

(02-22-2019 03:48 PM)Leviset Wrote:  ... there are 16 silver pins left on the LCD PCB - are they from the old cable and been left behind and do I need to remove them before I try out the new 16 pin ribbon cable I have?...

Looks like it's just a matter of desoldering the old pins and soldering the ribbon cable on. Is your friend not available?

Edit: https://www.buerklin.com/en/alphanumeric...m/p/71s328 looks like a match for the LCD, but minimum quantity is 128.

Edit2: possible sources for singles:

• https://www.elpro.org/gb/2-lines-16-char...yh-py.html
• https://octopart.com/dem+16223+syh-py-di...w2_OIDKA-g
  

Found by searching "DEM 16223 SYH-PY"

[BobVA]

Denny:

This Newhaven display at Mouser looks physically similar.

Maybe you could check the measurements and bounce the data/electrical specs off the boffins at EEVBlog and see if it might work?

[Leviset]

I went for the LCD suggested on Mouser but bought one from a local electronics store as you need to be aware that Mouser charge a minimum of £12 for just one item delivered locally in the UK. I did email them to ask why local (UK) postage was so excessive - they replied that they charge postage for a minimum of 100 items so their full cost for a £7 component with VAT and delivery would have been ≈ £24!

The LCD I did get however needs an operating voltage of 4.7 to 5.3v DC and the original LCD was driven by a CR2032 3v DC cell battery from the μWatch (there are 2 CR2032s in total but only 3v gets delivered to the LCD.
NOW to expose this Pure Mathematician’s ignorance of all practical application of Electronics again, could I power the whole watch and screen with an external 5v DC power supply as I’ve no intention to make it into a watch if I can get it going again, it’ll be used as a desktop.
Is there a larger voltage (4.7-5.3) DC coin battery the same size as the CR2032?
Please advise as I don’t want to ‘fry’ the whole watch!

[ijabbott]

(02-28-2019 12:00 AM)Leviset Wrote:  The LCD I did get however needs an operating voltage of 4.7 to 5.3v DC and the original LCD was driven by a CR2032 3v DC cell battery from the μWatch (there are 2 CR2032s in total but only 3v gets delivered to the LCD.

Have you measured Vlcd with the software running? It looks like it uses a charge pump to increase the display voltage.

[Leviset]

Ian,
I’ve meaus the voltage going to both the +ve and -ve contact points on the main watch PCB - the 2 CR2032s from the battery bay connect directly to them. It shows ≈ 3.3v DC - I do not know if the software is running or not as I can’t get anything on the screen.

[teenix]

(02-28-2019 02:58 PM)Leviset Wrote:  Ian,
I’ve meaus the voltage going to both the +ve and -ve contact points on the main watch PCB - the 2 CR2032s from the battery bay connect directly to them. It shows ≈ 3.3v DC - I do not know if the software is running or not as I can’t get anything on the screen.

Looking at he circuit, most of it runs directly from the battery. The LCD module is probably 5V as there is a simple charge pump circuit controlled by he PIC processor which supplies its power.

Sometimes, LCD modules look the same, but they may have slight differences in their instruction sets or in the procedures for resetting them at powerup and depends on the manufacturer. The module you picked, may or may not have this problem. If it does, the PIC will not be able to drive it properly.

If the circuit is running, you should be able to measure about 5V on pins 1(GND) and 2 (5V) where the LCD module connects.

The ribbon cable is a standard FFC type and should be replaceable if damaged. It looks like it can be repaired though, but would be a bit tricky because you would have to strip off a few mm of the plastic sheath to expose the conductors.

I would then try cleaning the black stuff off, probably with isoporopyl alcohol, clean up the solder pads on the ciruit board and then carefully resolder the ribbon cable back on. You will have to make sure it is the right way around beforehand. If the project is carefully re-assembled and not touched again, you might get away with leaving the black goo off, which is probably there for strain relief to stop the cable pulling off the solder points. It looks like that idea already failed however.

The LCD module will be sensitive to static discharges from your skin, so you need to take a bit of care while handling and repairing it.

cheers

Tony

[Leviset]

Success!!
I’ve adapted an old 5v DC power supply, removed the battery compartment all together and sent the 5v directly to the +ve and -ve connections on the main UWatch PCB. The new LCD sprung into life as soon as I pressed the Mode button and after displaying an (old) date, went to the Setup screen.
I’m assembling the watch on a flat breadboard and will spend tomorrow tidying all the new cables and connections neatly so I can use it as a desktop (albeit with a tiny 16 x 2 screen and a minute keyboard!).

I’m also thinking of powering it with 5v from a standard USB cable from a standard power pack I’ve already got UNLESS anyone thinks that might not be a good idea?
Should I be using a cable with a ferrite ‘choke’ on it or doesn’t it make any difference - I’ve always used ‘choke’ USB cables in my recording studio, especially when powering external audio interfaces, I was told they stop/reduce RFI & EMI interference which can appear as ‘noise’ on a digital audio recording (although the majority of my 18 track Recording Studio is based on ProTools with a DIGI 002 FireWire Audio Interface - although I also still use analogue Reel to Reel occasionally as well). I don’t know if or how RFI/EMI interference would affect a calculator though?
Using a rechargeable USB pack and an USB cable would make the Desktop μWatch portable and negate the need to have an AC 5v DC Power Supply plugged into the mains.
I think I’ve been lucky here as my whole repair has been based on just Logic (the LCD screen needed at least 4.7v DC so I went ahead changing the power supply to 5v, not having enough EE knowledge to know if that would cause other issues - some might say I used guesswork!) and I could have ended up ‘frying the whole thing?
I bought the right size of LCD screen replacement, not having checked that it had the same voltage requirements as the original (3.3v) - instead the new LCD needed 4.7v to 5.3v; I’m assuming that the μWatch was actually running under the old in parallel 2 x CR2032 3v batteries but that there wasn’t enough voltage to actually power output to the LCD? The other huge advantage (for me) was that the new LCD came with its 16 pin ribbon cable already attached to the LCD - all I had to do was to put the other end into the female slot on the μWatch and lock it into place as in no way would I have been able to solder the bare 16 pins of the ribbon cable to the LCD.

This has been a good hands on project (eventually!) for me. I’m trying to improve my EE knowledge with a combination of paid and free online courses.
So having completed the repair (I’m very grateful for everyone both on the Museum Forum and via email who offered advice as to how to proceed) I’m now contemplating a couple of things:-
(1) Is it possible to drive a bigger screen (preferably by piggy backing to the existing LCD so as not to have to remove - a bit like the dual screen setup I have on My Windows Recording Studio PC.
(2) what are the two male connectors on both edges of the μWatch circuit board? I think both are 5(6?) pin and are they UART serial connections (and/or IR?) - but for what purpose?
(3) Can either/both serial ports connect the μWatch to external accessories like printer, PC or storage device like tape recorder or minidisc to load and save programs?
(4) Can a larger keyboard be attached?

Thanks
Dennis

[grsbanks]

It's unlikely the watch will be affected by EMI and if everything else of yours is running on choked cables I can't see it interfering with them either.

As for the power pack, that is unlikely to work. Unless the device connected to a power pack is drawing enough juice, the power pack switches itself off, and I can't see the μWatch wanting to suck up anything like enough power to trigger it.