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Favorite method of assembling circuits at home?

  1. Oct 15, 2011 #1
    I just got my MSP-430 (microcontroller kit with two micros for $4.30) and I' just awestruck by how easy it is to use. I am looking to make a few very low-power circuits here and there for my car. For example, one to lock the doors after 30 seconds when I press a button.

    What do you guys like to use for actually physically constructing the circuit?
    - Breadboards are easy and require no soldering, but are larger and more expensive.
    - Stripboards are kind of weird and can't be re-used a lot
    - Wire wrapping appears to be expensive due to the cost of the tools

    Secondary question: what is the cheapest battery setup to get 5V? It seems all the normal battery sizes give multiples of 1.5V.

    Any I am missing?
     
  2. jcsd
  3. Oct 15, 2011 #2

    AlephZero

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    For experimenting, use breadboards. They are re-usable, and so are the components.

    For a permanent circuit, I would always use soldered connections, either on stripboard, etching a circuit board (the kit you need to etch small one-off boards isn't expensive and will last for years, apart from the consumables like the board itself),

    For a small circuit where it doesn't matter what it looks like and there are no issues with insulation etc, a 3D "rats nest" of self-supporting components can be a perfectly good construction method.

    5V power supplies: check the speciification of your kit to see what is absolute max voltage, and/or if it will work properly on 4.5V. A nominal 6V battery with a silicon diode in series to drop about 0.6V or 0.7V, and a smoothing capacitor on the "circuit" side of the diode, may be all you need. Unlike a resistor, the forward voltage drop across a diode is not very sensitive to changes in the current taken by the circuit.

    Otherwise, the 78xx and 79xx series of ICs are cheap and easy to use. They would be my obvious choice to power a 5V circut from a car battery, for example.
     
  4. Oct 15, 2011 #3

    Danger

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    Hi, King.
    I know almost nothing about electricity, and far less about electronics.
    That having been said, I liked the copper-clad perf boards when I was a kid. You lay out your own printed circuit with an etch-resist pen, then dump the thing in acid to eliminate the rest of the conductive surface.
    There's an alternate approach that I don't know if most electronics people even know about because it was specialized to the security industry (in which I was a professional). There are special pens which lay down a conductive ink. We used them in alarm systems. It's almost exactly the opposite of the etch-resist idea. You use a non-clad perf board, then draw your circuit upon it. The advantage to a perf board is that you just mount your components where ever you want to, and pass the leads through the holes. No need for drilling, which can be messy. (In the security business, they were used to draw traces on windows, which were undetectable, in place of the more common foil breakage detectors.)
    As for the battery thing, why not just use a 9-volt and regulate it down?

    edit: Oops! Hi, Aleph. You sneaked in while I was composing. I defer to you.
     
  5. Oct 15, 2011 #4
    I am concerned about power. My solution generally needs to last about a year.
     
  6. Oct 15, 2011 #5

    Danger

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    Is the thing stationary enough that you could use a wall-wart?
     
  7. Oct 15, 2011 #6
    https://www.youtube.com/watch?v=urv6jArKp6M

     
    Last edited by a moderator: Sep 25, 2014
  8. Oct 15, 2011 #7

    cmb

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    I've usually found that it is possible to pack almost any <50V circuit onto strip-board to a component-density so high that it is not possible to get any more components on! Further, if you keep your wits and make sure tracks are cut short so that they are only as long as they need to be, you put in 'guard' rails of ground/constant voltage, and you keep potential interfering parts of the circuit away from each other, you can construct operational boards to 10 MHz without significant signal degradations/self-inteference.

    In other words, I don't think there is much you can't do at amateur level with stripboard, and other options do not have clear advantages over it.

    For 5V power, I tend to use 5x AA rechargeable batteries with low discharge rate (eneloop) for my circuits, regulated with LM2931, which means you'll still get to suck some juice as the batteries tail off and if your circuit draws, say, 2mA then you'll get 1,000 hrs over a year's service (as 'regular' voltage regulators tend to suck up 5mA for themselves just doing nothing at all, which hurts battery life if we're talking low current circuit).
     
  9. Oct 15, 2011 #8
    I left out some crucial information. I don't have a soldering iron so I'm including that in the start-up cost of any method that requires one. Yeah, I know...
     
  10. Oct 15, 2011 #9

    Danger

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    On the other hand, if you have a pair of pliers, a nail, and a stove, you have a soldering iron. It's intermittent, and not glamourous, but it works. :biggrin:
     
  11. Oct 15, 2011 #10

    cmb

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    Just buy one off ebay for a couple of bucks.
     
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