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November 04, 2008

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OMG this is my first post!! how awesome!

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Switch Matrix

How do you drive 64 lamps and read 64 switches from a microcontroller (in my case a raspberry Pi) that only has a limited amount of io pins? Easy answer *might* be to use a beaglebone black, one of which I own, but where would be the fun in that? One of my requirements when rebuilding the Gameshow machine was to minimise the amount of cabinet rewiring needed. The idea would be to figure out where the lamps/switches/coils/whatever connect to the circuit boards, and build my boards to accept those connectors. Now, pinball lamps and switches are usually controlled using a matrix. The basic overview looks a little something like this: The idea is that the cpu energises the rows in sequence (1P10 - the white/something wires) and then once a row has been energised, it has a look to see if there is any activity on the columns (1P8 - the green/something wires). An excellent article on switch matrix theory can be found at http://pinballrehab.com/1-articles/so...

On Western Digital hard drives, PUIS and Rocket Raid controllers

Disclaimer: This procedure worked for me. Use at your own risk. It uses software not written by me and downloaded randomly off the internet. If you break something, it isn't my fault. So a while back I bought 4x1T WD green hard drives (WD10EACS) and a rocket raid 1740 to use with them. I eventually ended up using them as JBOD (turns out it didnt support hardware raid 5) for a few years with no problems. This was until I upgraded my server with a motherboard that supported enough sata drives and no longer needed the raid controller. Turns out, if you ever set staggered spin-up on these drives as I did, it sets some internal flag on the drive to use a thing called PUIS or Power Up In Standby. This means the drives don't actually start spinning until they receive a request for some data. Problem is, these particular drives don't support it (or something) and some sort of hack is in place in the rocket raid controller to get around thi...

The Centurion

Have you ever played the brutal drinking game called the Centurion? It goes like this - have one shot of beer every minute for 100 minutes. It may not sound like much, but if you think about it, a 30ml shot 100 times is 3 litres of beer in a little under two hours. Anyway, I've played this a few times and the biggest problem is keeping track of time and who has drank what. Usually you need a timekeeper who isn't playing to ensure that all drinks are taken and that we drink at the appropriate time. Well, for an upcoming bucks weekend (mine), I decided to remedy this. I build it into an old tool case I had lying around. There are 8 double seven segment displays to keep track of players scores, all driven by 595 chips attached to transistor arrays. I decided not to use a 7-seg driver chip because it would have been more of a pain to solder. The 595 and ULN2803 transistor array can pretty much be mounted side-by-side. Since I didn't...

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