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Basic problem with transistors

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by giftiger_wunsch, Jul 25, 2009.

  1. Hero999

    Hero999 Banned

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    The spacing (pitch) on the connectors I linked to, is 2.54mm/0.1", measured from the centre of each pin; it says so on the RS catalogue page.

    The spacing on the connectors you specified is 2mm measured from the centre of each pin; it says so on the Rapid catalogue page.
     
  2. giftiger_wunsch

    giftiger_wunsch New Member

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    I noticed that one, but I must have missed where it said that on the link you posted. I'd better measure the distance between the terminals on my prototyping board carefully and hope it's actually 2.54mm :p I believe I may have seen a 2.54mm header on rapid, though I've lost the link now; I'll find it again if I discover it will be appropriate. If the spacing of the terminals on my PCB is 2.54 rather than 2.50 then problem solved :D

    Edit: I measured the distance between the centre of the first pin and the centre of the last in the row, and the average distance between pins was 2.52mm. Hopefully my means of measuring them was inaccurate and they are actually 2.54 :D


    Back to the RS delivery cost problem though, do you know if they make some sort of distinction between registering your details with RS and being 'an account holder'? :confused: As you suggested, their site indicates that free delivery is granted to account holders, but £4.95 appeared as the delivery cost even though I registered (though not by choice :rolleyes:)
     
    Last edited: Aug 13, 2009
  3. Hero999

    Hero999 Banned

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    Providing you drill the holes large enough, it shouldn't make much difference whether it's 2.54 or 2.5mm.

    13×2.54 - 13×2.5 = 0.52mm so make sure the holes have a diameter of 1mm and it should be fine and make the pads as large as you can, just in case.

    Heck I drilled a 40 pin ZIF socket at 2.5mm pitch when the pitch of the ZIF was 2.54mm, it wouldn't fit so I drilled the holes a little larger and it fitted perfectly.:D
     
  4. dave

    Dave New Member

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  5. giftiger_wunsch

    giftiger_wunsch New Member

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    Woah, you misunderstand. I can't go drilling into my development kit's prototyping board :eek: the holes are where they are and I don't think there's anything I'll be able to reasonably do about that.

    Still, as you pointed out the difference is only 0.52mm and the holes are 1mm in diameter so there shouldn't be a problem. I think I may have miscalculated by a factor of ten when I worked it out, and was worried about having to fit it to something 5.2mm too wide. Even ignoring the fact that the holes are 1mm wide which is wider than the error margin, 0.52mm wouldn't exactly require much flexibility to accomodate.

    The more I think about what's going to be required here the more I think I'll probably be better off getting the equipment to etch my own PCBs rather than try to build this device using stripboard. If RS sell this equipment, perhaps that will put my balance up enough for them to throw in free delivery. If not, it should be enough for rapid, and their prices seem similar. I'll probably try to find a cheap etching tray, etch-resist pen, etching fluid, and blank PCBs.

    Looks like I'll have to increase my budget, though at least the etching equipment will be useful in future.
     
  6. Hero999

    Hero999 Banned

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    The component leads should also bend a bit, providing they can bend 0.26mm either way, it doesn't matter.

    I find Rapid to be generally much cheaper than RS but there are exceptions. Take the ZTX690B £0.73 from RS, £0.38 from Rapid, the resistors, £0.01/per unit from RS, £0.005 per unit from Rapid, although this is negated because Rapid have a minimum order quantity of 100 and RS only have a MOQ of 10.
     
  7. giftiger_wunsch

    giftiger_wunsch New Member

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    Yeah, that's what I expected.

    Providing I can get all of the components I require from rapid, I think I'll be ordering from them. It turns out RS only do free delivery to business customers, private customers have a minimum delivery cost of £4.95. With the addition of etching equipment my order will be easily over the £30 minimum for free delivery with rapid.
     
  8. Hero999

    Hero999 Banned

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    May be I accidentally told them I am a business, perhaps you could make the same honest mistake. :D
     
    Last edited: Aug 13, 2009
  9. giftiger_wunsch

    giftiger_wunsch New Member

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    Okay 5th and final time I edit over this message, I found the 100-packs of resistors now. It's slightly ironic they sell them for 17p each or 50p for 100...
     
    Last edited: Aug 13, 2009
  10. giftiger_wunsch

    giftiger_wunsch New Member

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    Heh heh. Ironically, they wanted the name of my business even though I didn't tell them I'm a business, and when I was forced to make something up, they wouldn't give me the free delivery proffered to business customers...

    Anyway, rapid are cheaper on every component except resistors and do free delivery if the order's over £30 so :D


    Edit: ...remind me never to buy from RS. They wanted to charge me £10 for a polystyrene etching tray, whereas maplin sell polypropylene trays for £1.45 each :eek:
     
    Last edited: Aug 13, 2009
  11. Hero999

    Hero999 Banned

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    They don't sell cheap ¼W 5% carbon film resistors in smaller quantities than 100.

    I don't know what your 17p resistor was but it certainly won't be cheap ¼W 5% carbon film.


    Rapid are cheaper for resistors, it's just the minimum order quantity gets in the way.

    Still resistors are cheap and it's always good to have a fairly large stock of them.

    If you need to top your order up to £30, I'd recommend buying a resistor kit.

    E12 ¼W resistor kit
    E3 ¼W resistor kit

    It probably works out more than buying them all in packs of 100 but it's more convenient to have a set of resistors, especially the E3 values which are really common.

    I generally find RS cheaper than Maplin but there are exceptions.
     
  12. giftiger_wunsch

    giftiger_wunsch New Member

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    I believe it was carbon composite, but it kept popping up top of the list when I searched for carbon film. It was also 0.25W, but at that price I assume carbon composite = some kind of super resistor :D


    I already have an E12 resistor kit (it is indeed useful), and I've found some extra stuff to top my order up to £30 with.

    EDIT: By the way, I am slightly disgruntled to find that rapid sell the same resistor kit for £2 less than I bought mine for from maplin :rolleyes:


    I have a few noob questions if you don't mind? :eek:

    1) Is ferric chloride etchant suitable for use with a simple polypropylene etching tray? The etchant description suggests 3 expensive tanks it's suitable with, but I get the impression they're just listing tanks made by the same manufacturer.

    2) The "2-way header plugs" here are the plastic connectors which go on the pins of the header on the same page right? There are no images of the connectors so I wanted to be sure.

    3) Would this coping saw be suitable for cutting through PCB material?

    4) I added some 20AWG wire to my order; I have some thicker wire but I only discovered when I bought it that it was too thick to fit into my breadboard. I looked up the actual diameter of 20AWG to be around 0.9mm; that should fit in my breadboard right?


    Sorry for all the questions, and thanks a lot for all of the help you've given me :D I'll repay the favour when I become better at electronics and you're stuck with something :p :D
     
    Last edited: Aug 13, 2009
  13. Hero999

    Hero999 Banned

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    1. Yes, a polypropylene etching tray is perfect for ferric chloride.
    2. The two way header plug, just has two pins. I can't find a 26 way double row or 13+13W double row (as it would be listed here. My advice is to use a 36+36 way header and cut it down to size. Also don't rely on images in cataloges they're just for indication and are often wrong. I don't know about Rapid but there's a disclaimer regarding this in RS's terms and conditions.
    3. Yes that coping saw will do and is fine for cutting round corners though difficult to cut straight with. If you want to cut in a straight line then I'd recommend a hacksaw.
    4. Is the 20AWG wire multi-core flexible cable or is it solid? I just get away with pushing 0.5mm² flexible cable through Veroboard and 20AWG is 0.528mm². If you can get away with it then I'd recommend it because it should be all right up to 3A (with outer insulation, like mains cable) and 5A unsheathed (single conductor surrpounded by air).
     
    Last edited: Aug 13, 2009
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  14. giftiger_wunsch

    giftiger_wunsch New Member

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    1. Yeah, I realised that and that's fine. It's unlikely I'm ever going to use all of the parallel port bits for one application, and if I need to use several I can just use several of the 2-way plugs. I want to ensure that the plugs are the connectors which you would feed wires into which can then sit on the pins of the connectors though... your answer seems to suggest I've got it wrong.

      I'm getting several of the 36-way single row headers, I'll cut two down to 25 (perhaps the coping saw will work for that too?) and use them for the parallel ports, and then I have another 5 for miscellaneous other uses. Conveniently, the power connectors from the motors on the robotic arm use 2-way connectors for 2.54mm pitch headers. (It's more of these connectors that I want, rather than a load of 2-way headers.) In fact some single-pin connectors also be very useful to have, since individual connections will typically need to be made between a single parallel port bit and GND, on a separate part of the board.

      It's listed as 'semi-rigid'. Perhaps I should use 22AWG instead?
     
    Last edited: Aug 13, 2009
  15. Hero999

    Hero999 Banned

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    Solid cable tends to be easier to fit through the holes than multi-core.

    I don't know what semi-rigid means, it's probably best to check the datasheet.

    My guess is that it will fit Veroboard but I don't know about stripboard.
     
  16. giftiger_wunsch

    giftiger_wunsch New Member

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    I've noticed that; I've had to trim down a couple of cables I've used with my breadboard a couple of times as the individual strands are delicate and have a habit of getting caught in the breadboard and detaching.

    Anyway my only remaining problem is if the term 'header plug' as opposed to header itself doesn't refer to the connector which fits round the pins, what is the name of this component?
     
  17. Hero999

    Hero999 Banned

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    A plug has pins (male) a socket has holes (female), when the pins are inserted into the holes they make sweet love. :D
     
  18. giftiger_wunsch

    giftiger_wunsch New Member

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    Thanks for the graphic detail :D I'll need 2-way sockets rather than plugs then. The other components on the page don't specify either socket or plug, I hope I'm safe in assuming they're plugs.

    It strikes me that calling a wall supply a 'plug socket' is somewhat ironic giving those definitions :p


    Odd, I searched for header sockets and the only results were 'DIL Sockets' and 'DIL Sockets' which both have pins... transvestite perhaps :D? Moreover though, there don't seem to be any one- or two-way header sockets :(
     
    Last edited: Aug 13, 2009
  19. Hero999

    Hero999 Banned

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    By the way, you should always use solid single core cable for breadboard. If you must use stranded wire, then tin the end you're inserting beforehand.

    Oh I forgot to respond to this:
    Carbon composite is good for withstanding overloads and is old fashioned to valve enthusiasts like them. I don't see the point as you can buy 1W carbon film resistors for much less.
     
  20. giftiger_wunsch

    giftiger_wunsch New Member

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    Thanks, I'll remember that in future. Any idea how I might be able to obtain suitable connectors? They can't be that difficult to find, they're used for the power/reset switches, LEDs, etc. on virtually any computer.
     
  21. Hero999

    Hero999 Banned

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