Hardware lesson with Gert: make your own ribbon cable connector

13th of June 2012 by liz

Someone in our forums was asking yesterday where he could buy some ribbon cable with a press connector for his Raspberry Pi, to attach to the GPIO pins. Pre-built cables like this are hard to find, and the options other people on the forums found were pricey, and also attracted large shipping costs. So Gert stepped in: here’s how to build your own using parts (which you should be able to buy from your local electronics store).

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48 comments

Tom on
June 13, 2012 at 5:24 pm said:

Very good tutorial! Thanks for including the little squeezy wire stripper.

Comment ↓
Stevep on
June 13, 2012 at 5:27 pm said:

If you’re a hoarder you may have a 26 way ribbon cable from an old computer – I think they were used for floppy drives. Just cut off the end you don’t want.
26 way connectors are very cheap from Rapid Electronics – http://www.rapidonline.com/Cables-Connectors/26-Way-Cable-Mounting-Socket-19-0315
Ribbon cable – Rapid only do 50m rolls, but there are eBay sellers who do it by the metre http://www.ebay.co.uk/itm/Grey-Ribbon-Cable-Wire-26-Way-Per-Metre-/300723084485?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item46047e1cc5#ht_1658wt_907

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Darren on
June 13, 2012 at 6:25 pm said:

Seems not many places stock the 26-way IDC connector, as it is a slightly unusual size.

Comment ↓
- Stevep on
  June 13, 2012 at 6:46 pm said:
  
  ???
  Apart from 2 sellers on eBay, Rapid Electronics, RS Components and CPC Farnell….:)
  
  Comment ↓
  - Darren on
    June 13, 2012 at 6:54 pm said:
    
    I was thinking more along the lines of maplin, because places like Rapid and RS have minimum order charges that puts the price up a lot if you just want a couple of small items. But then I suppose Maplin pretty much only sell toys these days so is to be expected.
    
    Comment ↓
- Gert van Loo on
  June 13, 2012 at 7:02 pm said:
  
  I tried to find them and for some reason they are very difficult to FIND. It seems most vendors stock them under widely different names. Only if you hit on the exact right (vendor) description do you suddenly find a plethora with each vendor. I found 57 at Farnell, 18 at RS, None (yet) at Digikey, but I am 100% sure they have them. “IDC 26″ worked best thus far.
  
  Comment ↓
  - Tim Keck on
    June 13, 2012 at 7:14 pm said:
    
    Digikey has HKC26S-ND, manufacturer part AWP26-7540-T-R, $0.56 each, 1030 in stock.
    
    Comment ↓
  - Randy Glenn on
    June 13, 2012 at 7:15 pm said:
    
    At Digi-Key:
    ED10505-ND
    HKC26H-ND
    HKC26S-ND
    HKR26H-ND
    MKC26E-ND
    (and many more – about seven pages worth)
    
    They’re under
    Connectors, Interconnects
    >
    Rectangular – Free Hanging, Panel Mount. I used 2 row, 0.100″ pitch, 26 connections as filters.
    
    (Digi-Key’s categories for connectors always confuse me)
    
    Comment ↓
Randy Glenn on
June 13, 2012 at 6:30 pm said:

Adafruit looks to sell one specifically for the Pi:

http://www.adafruit.com/products/862

Not too bad at $4. Plenty of other goodies to get there if you’re looking to round out an order

Comment ↓
- Randy Glenn on
  June 13, 2012 at 6:33 pm said:
  
  My mistake – didn’t realize that was literally the first response in the forum thread.
  
  Comment ↓
jfedor on
June 13, 2012 at 7:07 pm said:

Can I use a hard drive cable? (The old kind, IDE, not SATA.)

Comment ↓
- Gert van Loo on
  June 13, 2012 at 7:12 pm said:
  
  Only the old (coarse) type. The cable strands should be 0.05″ (0.127 mm) apart. Later the high-density (80 wire) cables came. You can’t use those. Of course as mentioned you can use the old 34-way floppy disk cable and cut it down to 26 wires.
  
  Comment ↓
  - Stevep on
    June 13, 2012 at 8:22 pm said:
    
    I must have struck lucky then, as the one I found in my box of junk was a 26 way, from way back when I built a few windows boxes. Have no idea what they would have been used for originally, obviously not floppy drives from what you say.
    I’m looking forward to being able to connect it to a Gertboard of course….!
    
    Comment ↓
    - spiny on
      June 13, 2012 at 8:30 pm said:
      
      it might have been an old joystick port ribbon connector, the old type that went from a connector on the soundcard to a port on the back of the case.
      
      Comment ↓
      - Bernard Klatt on
        June 14, 2012 at 7:59 am said:
        
        No, not for a joystick (they were 15-pin), a 26 conductor cable most likely was for a parallel port (DB-25F) or possibly a RS-232 (DB-25M) serial port.
      - Adam on
        June 14, 2012 at 5:58 pm said:
        
        there was also an old bus CD-ROM standard (Philips?) that used such a cable.
William H. Bell on
June 13, 2012 at 8:32 pm said:

Hi,
It is really important to keep an eye on the cable and keep it still as Gert says. We had to make many of these cables in the lab. It is essential that the cable is kept pointing along the plane. If the cable moves to the right or left in Gert’s video, it is possible to connect two wires to one pin. When making these cables up in the lab, we used to test each pin with a digital voltmeter too.
Best regards, Will

Comment ↓
Whoop John on
June 13, 2012 at 9:00 pm said:

The next question will be ‘How do I interface 3.3v logic with 5v logic?’

Fortunately this can be done for two way traffic, such as an I2C bus, with two pullup resistors and a MOSFET.

http://www.hobbytronics.co.uk/mosfet-voltage-level-converter gives a typical example.

Comment ↓
guitar1 on
June 13, 2012 at 9:33 pm said:

you could also use old intern usb or firefire (or others) headers and glue them together … it worked very well
https://plus.google.com/u/0/109215046466232858854/posts/V8psc4GoFsy

Comment ↓
- Darren on
  June 13, 2012 at 11:22 pm said:
  
  I just checked an there is enough space to fit up-to a 30-way (2×15) IDC connector without having to cut the plug down as there is some extra space between the last pin and the composite video connector. So if you can’t find a 26-way then 28 or 30 would also work.
  
  Comment ↓
  - guitar1 on
    June 14, 2012 at 9:08 am said:
    
    exactly, this had made it much easier
    
    Comment ↓
Reggie on
June 13, 2012 at 9:42 pm said:

Just thought I’d point out that old PC’s that have a printer port on a pci card backplane will most likely have a 2×13 IDC cable on the other end.

Comment ↓
Zomzilla on
June 13, 2012 at 10:37 pm said:

Used an old 40 wire from a Jurassic Dell.

The real challenge is trying to use the wires with a breadboard…

Comment ↓
- Darren on
  June 13, 2012 at 11:15 pm said:
  
  A better option with a breadboard is to use some female to male jumper wires such as maplin (A39GF) or tandyonline (276-156). Alternatively if you want to make your own then if you use a ribbon cable with a female plug on each end then you can make your own set of jumpers by soldering a pin header with some heat shrink sleeving on the end of a length of jumper wire that you can then insert into the IDC socket.
  
  Comment ↓
Matt Hawkins on
June 13, 2012 at 11:27 pm said:

I tried using an old floppy drive cable but ribbon cable just gets messy. I have had more success using the cables you use to connect CD-ROMs to sound cards. They aren’t much use these days and I had loads of them in the loft. Cut them in half and you get a 1×4 pin connector with some wires that are easier to handle. Three of these and I can connect 5V, 3.3V, ground and a few GPIO pins to my breadboard.

Comment ↓
Kashif Ali on
June 13, 2012 at 11:54 pm said:

Gert is a genius ! I wish I had a teacher like that in University

Comment ↓
klappy on
June 14, 2012 at 2:51 am said:

I used an old school floppy cable after cutting off the portion that was twisted to avoid pinout confusion. Then with an ugly soldering job, lined up a few row of pin headers for a nice adapter to connect the gpio to a solder-less breadboard for easy prototyping as shown in the following shot: http://instagr.am/p/Lyek5gA81x/

Comment ↓
- AndrewS on
  June 14, 2012 at 10:19 am said:
  
  Like it, great idea
  
  Comment ↓
  - Jim on
    July 31, 2012 at 1:50 pm said:
    
    Superb! Inspired hardware hacking. Gathering my old cables and headers now, getting ready to start soldering my own breakout board adapter.
    
    Comment ↓
AndyW999 on
June 14, 2012 at 8:05 am said:

It’s also a lot easier if you can get ‘rainbow’ wire rather than the grey flat cable as it’s easier to split and the colour coding cuts down on wiring mistakes!

Comment ↓
- Gert van Loo on
  June 14, 2012 at 1:32 pm said:
  
  There is a big disadvantage to rainbow wire: you have to know where pin1 is. Unless you ‘happen’ to know the colour code sequence (black, brown …) it does not make sense. So for most the users the ‘red wire is one’ is less likely to cause confusion.
  
  Comment ↓
  - Whoop John on
    June 14, 2012 at 6:20 pm said:
    
    Erm totally not politically correct, but I learned it as a kid from a UK electronics magazine and never forgot it.
    
    Bad – Black
    Boys – Brown
    Rape – Red
    Our – Orange
    Young – Yellow
    Girls – Green
    But – Blue
    Violet – Violet
    Goes – Grey
    Willingly – White
    
    Comment ↓
    - liz on
      June 14, 2012 at 6:29 pm said:
      
      The dirtier a mnemonic, the easier it is to remember. I applaud your political incorrectness.
      
      Comment ↓
      - AndyW999 on
        June 15, 2012 at 10:08 am said:
        
        It’s the same as the resistor colour code – which I regret admitting to know from a very early age.
        
        I will correct the above :-
        
        But – Blue
        Virgins – Violet
        Go – Grey
        Without – White
    - imm on
      June 16, 2012 at 9:48 pm said:
      
      I always had:
      Bye Bye Rosie, Off You Go, Birmingham Via Great Western.
      No idea what it means, but I’ve remembered it since, erm… I can’t really recall when I learned it… Must be 40 years now… or more…
      
      Comment ↓
furf on
June 14, 2012 at 11:55 am said:

Samtec ( http://www.samtec.com/ ) makes some awesome connectors and cables AND gives free samples (with free expedited shipping!). You can easily get what you need there for free. Show your love when you like them and actually buy some stuff.

Comment ↓
reiuyi on
June 14, 2012 at 8:31 pm said:

Green vulpen

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juanRIOT on
June 15, 2012 at 12:11 pm said:

That simple?! Thank you Gert.

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Romilly Cocking on
June 15, 2012 at 6:11 pm said:

Tandy are now back in the UK http://www.tandyonline.co.uk/ and are selling the 26-way connectors, cable and a crimping tool, which I find easier to use than the vice.

Comment ↓
Brian on
June 15, 2012 at 10:05 pm said:

£4.74 from here
http://www.ebay.co.uk/itm/26-Way-Ribbon-Cable-Assembly-for-Raspberry-PI-/120916565185?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item1c27305cc1

Comment ↓
imm on
June 16, 2012 at 9:41 pm said:

FWIW, just another vote in favour of using old floppy disk cables – yeah, they have too many pins, but there’s plenty of room for the end to overhang and I have loads of em in my old junk box…

Comment ↓
James on
June 17, 2012 at 3:22 pm said:

There are a few sellers now on ebay that are selling these :

http://www.ebay.co.uk/itm/Raspberry-Pi-GPIO-26-Way-Ribbon-Cable-Single-Ended-150mm-/270998890795?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item3f18cae92b#ht_500wt_1202

Comment ↓
Martyn Jones on
June 18, 2012 at 6:19 pm said:

The wonderful BBC Micro used / uses a 26 pin IDC header plug on its printer cables – so if you can find one of those it should do. Many of us old computer / ICT teachers should be able to lay their hands on one somewhere either in their school store cupboard or their garage at home (where most of my BBC stuff ended up).

The plug is actually called an IDC header which stands for Insulation Displacement Connector because when you squeeze the plastic together the pins are sharp enough to cut through the ribbon cable insulation and make 26 connections at once – fantastic when it works, but can be a pain if the cable is not in squarely (as many of us who tried to make their own cables can testify!). Their should also be a clamp on the top of the plug through which the ribbon cable is looped back – this avoids ripping the cable off the pins when you try to take it off the connection (and which is very easily done).

I might as well throw in the fact that the BBC Micro was excellent for interfacing to the real world (as many of you will know) – it had a 20 pin User Port with input and output lines that could be controlled by software. I used to use this for controlling allsorts of devices including lights, relays and stepper motors. This, in my opinion, put it head and shoulders above any of the other home computers of the time, although many American home computing history websites don’t even seem to realise that the BBC Micro ever existed.

Comment ↓
- liz on
  June 18, 2012 at 7:00 pm said:
  
  The Beeb’s User Port was one of the things that convinced us that bringing out GPIO on the Raspberry Pi was the right thing to do. I’m very glad we did; there are some superb hardware projects going on at the moment which make good use of it.
  
  Comment ↓
Simon Spencer on
June 23, 2012 at 11:57 am said:

I suppose the alternative is, if people aren’t comfortable with making the component, the company could always resurrect the ribbon cable and sell it on the website. That way people are able to use them with Raspberry Pi, and the company is earning a little extra revenue to help manufacture more of the devices.

Comment ↓
Anne on
July 5, 2012 at 1:49 am said:

Neat! But if you have an ancient PC lying around, there’s a decent chance there’s a ribbon cable connecting the motherboard to the parallel port that is compatible.

Comment ↓
Richard on
July 12, 2012 at 8:21 pm said:

You can also use a 40-pin IDE (ATA) disk cable – these were the standard on most PCs till a few years ago, and should be widely available. Obviously you have to be careful when offsetting it.

Comment ↓
Phil on
December 13, 2012 at 9:28 am said:

Do NOT use old floppy cables (34 pin), IDE/ATAPI drive cables (40 pin), or other oversize cables.

Look for old PC compatibles – the dime a dozen type from 2006 or earlier. They aren’t hard to find and generally available for free. Look for one which has a DB-25 (male or female) connector on a backplane connector or somewhere else on the back of the case (e.g. a DB-25 which is not mounted directly to the motherboard).

If it’s a female DB-25 it’s probably a printer port, if it’s a male it’s certainly a 25-pin serial port. In both cases the end which plugs into the motherboard or I/O card will certainly be a IDC-26 pin connector – the EXACT connector for the Raspberry Pi GPIO connector.

You can cut off the DB-25 connector and split apart the wires, or purchase a DB-25 to breadboard connector which will plug into a solderless breadboard or your circuit board. Since it’s a 25 pin connector one of the 26 pins isn’t connected (I’ll have to check which one – it’s one of the ones on the end). If it’s an important pin you can reverse the cable, although you should carefully mark the new pin one on both ends to avoid confusion.

BTW – if you’re in the Orlando Florida area Skycraft electronics has crimpable IDC-26 pin connectors right next to the cash registers.

Comment ↓

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