|flat flex cable ideas - last might be best!|
Message #22 Posted by Ellis Easley on 5 June 2003, 8:43 a.m.,
in response to message #21 by David Ramsey
It shouldn't be hard to specify the cable. It is a standard pitch, 0.1", and has 13 conductors. Just measure the total length and make sure you get something at least that long - I measure 2.75". It might be possible to get them in different "phases" by which I mean whether the stripped part is on the same side at both ends, but I don't think so. The two outer layers are different, the thicker and tougher side isn't meant to be stripped - notice how it is flat and the other side follows the contours of the conductors. I've seen applications where the stripped portion of the cable is folded over to put the exposed conductors on the other side.
Now that I've measured the cable, I'll post the dimensions as a response to Renato, he said he saw some cable assemblies in a shop.
The only thing I find in the DigiKey online catalog is 500 foot rolls of 0.1" flat flex cable, on the first page of these two (I'd like to know the proper way to strip the cable - I think a vendor once told me they use something like a grinder or a wire brush):
On the second page they have prepared cable assemblies but only in 0.5 mm and 1 mm pitches. These might work via redundancy, like zebra strips, except the widest they have is 31.15 mm (30 conductor, 1 mm pitch). The first page shows the overall width of 13 conductor, 0.1" pitch is 1.4" or 35.56 mm. You might have success with two 36 conductor, 0.5 mm pitch cables (18.5 mm wide overall), letting them overlap a little in the middle - or trimming the extra insulation on the inside edges - with two equal width cables, and an odd number of "destination conductors", the gap in the middle falls right on conductor #7. 0.5 mm pitch has 5 conductors in the space of 1 in a 0.1" pitch cable, so it might work.
I tried one more thing on the DigiKey website - I did a keyword search for "flat flex cable". The search results were divided into categories, I chose " Cable Assemblies -
Flat Flex(1194 items) ". That took me to a page with a sort of nomograph - you choose " Contact Termination "," Length "," Number of Contacts " and " Pitch ". For Termination I chose " Solder Tab/Solder Tab " which I assume means just stripped ends [turns out I was wrong - see below]. For length I chose 3", for number of contacts 13. For pitch, the only choices were 0.05" and 0.1", which I chose. Then I clicked on "Apply Filters". It came back with a part number, A9AAT-1303F-ND, and a price, $2.52 for one piece. It also said " Quantity Available 0 - Value Added Item " which tells me DigiKey will make it (or have it made) to order. Electronics parts dealers love this kind of thing - since years ago when TV's and radios were repaired, and a parts shop could build you a potentiometer with switch, multiple sections, etc.
I can't give you a link to the final page, you'll have to start here and make the same choices:
Make sure you don't click on " Items in Stock " on that page!
OOPS! They had highlighting on that part number, it took me to a catalog page - these aren't just plain stripped ends, they have flat terminals crimped onto the ends which are about the size of DIP IC pins. Here is that page:
I've seen these before - Tandy used a long one about 1" wide to carry some signals across a board but I can't remember exactly what product it was. But I think this kind of termination is supposed to be an improvement over the stripped ends, because it doesn't have the problems of delamination and "smiling" sockets. They are made to plug into a SIP (Single Inline Plug) socket - like what resistor packs plug into for SCSI termination. They might mate with the existing sockets in the calculators.
I tried some other paths from the "flat flex cable" search results - I zeroed in on the 0.5 mm and 1 mm cable assemblies and the 500 ft roll of 0.1" cable.
Here's an idea - order the terminated cable (maybe a little longer, like 4", in case you try my final idea). If you don't like the way it fits in the existing sockets, you could get some SIP sockets (or cut a DIP socket in half) or you could cut off the ends and try your hand at stripping the insulation from the ends. The more I look at the cable from my 97, I think a Dremel with the 1" diameter wire brush would probably strip it pretty well (bristles moving toward the cable end). I would try to keep the brush just over the conductors and not try to remove the insulation between the conductors.