LCD clock projector update

[Antoinette J. Citizen]

I came into the hackerspace a couple of months ago working on a projection clock - with a 10mm LCD screen. Everyone was very helpful - so I wanted to thank you for pointing me in the right direction.

I managed to get the LCD working!  It needed network resistors on the COM lines and each COM line to be pulsed separately in succession. I have attached some pictures and code below.

The only problem I have now is with the plastic ribbon cable connection - I have just been soldering it on at a low temp - but it seems to lose connection after a day or so.

I think I need to connect it with a pulse heat bonding machine - like this. So trying to research where I could get access to one- or if there is a place I could get it sent off to.

Does anyone know anything about these pulse heat bonding machines or alternative methods? 

This is the Arduino code I wrote to get it working:

https://github.com/acitizen/LCD/tree/master/LCD_DIGITS_BASIC_TEST

Basically, it needs to go through this cycle for each of the 3 COM lines in succession:

ALL COMS - SET AS INPUT

ACTIVE COM - SET AS OUTPUT 

ACTIVE COM -  HIGH 

Segments Visible - LOW

Segments not visible - HIGH

DELAY for 2ms

ACTIVE COM -  LOW 

Segments Visible - HIGH

Segments not visible - LOW

DELAY for 2ms

This is how it is multiplexed:

and the resistors on COM lines:

[Robert Powers]

Hi Antoinette,

What does this ribbon cable connect to? A PCB?

You could try solder paste and a hot air pencil, both can be found at the CCHS (I think). Liberally use Kapton (polyimide) tape to protect nearby heat sensitive elements. The preheater can also be a boon. I suspect you'll have success this way unless I'm picturing your situation incorrectly.

Good luck,

Bob

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[Antoinette J. Citizen]

The ribbon cable is a flexible printed circuit I believe. It is adhesive on the reverse side. I have been removing the cable and trying to adhere it with heat to a circuit board I made. But it only works temporarily. 

Possibly if I left the cable connected to the original circuit board, and cut the pcb down to size - I could use solder paste and a hot air pencil to attach wires to the adjacent solder pads? I tried to do this before using soldering iron and solder- but the pads were a bit too small for me to do this successfully. But I will try with the paste.

This is the original connection, the smaller cable at the top of the image goes to the LCD:

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[Adric Landman]

That's great work. I remember trying to work out what was going on with that projector!

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