Barebones Arduino


Following on from the single board Arduino Boy, see Chiptunes, I thought that it would be prudent to make some notes about barebones Arduino schematics, that can then be incorporated into single board designs

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Antiquated OS X


How does one get hold of an older version of OS X? There are dodgy google drive links available on eBay, from Russia (with love) for £3, or a shop in Fortune Town that offers pirated DVDs for £6. None of which are particularly good, or trustworthy, options.

The AppStore would be the best and safest option, but it is not cheap, and if you haven’t already purchased Mountain Lion when it was available, then it will not show up.

So, you have to buy direct from Apple (see links below), for $20. Or try to find a second hand version of a DVD, but on eBay they generally go for more than $20, when postage is included.

However, post-Snow Leopard, the OSes were more commonly released on USB sticks. Also, to install Lion or Mountain Lion, you need to be running Snow Leopard or Lion (respectively), so it seems that you need both the Snow Leopard DVD and then the binary of Mountain Lion – this is getting long winded and pricey…

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Capacitor set – electrolytic


The prices for electrolytic capacitor sets vary rather wildly.

Voltage Rating

The thing to remember, or to look for, is the voltage rating, as some kits come with 10 V capacitors (in particular the high capacitance 100 – 470 µF range), which aren’t much use in a 15V synth circuit, using CMOS 4000 logic ICs (although they would be OK in a 5V TTL circuit).

Rules of thumb

  1. Really it is best to get capacitors rated at twice the supply voltage (and round up to the nearest available capacitor rating), to be safe. So for 5 V use 10 V rated capacitors, for 12 V use 25 V rated capacitors, and for 15 V supply use 50 V rated capacitors.
  2. If you like living a little more dangerously, use a supply voltage between 2/3 to 3/4 of the voltage rating of the capacitor. So for 5 V use 10 V capacitors, 12 V use 16V capacitors, and for 15 V supply use 25 V capacitors

The only downside of using an over-rated capacitor is that a layer of oxide may develop within the capacitor.

Sources: Selecting voltage rate for capacitors and High Voltage Capacitor, in a low voltage system?

AliExpress is cheaper than eBay generally.

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