Soldering Practice

While I have been reading and building a few things on my own, process is a little slow going due to time constraints.  It's probably going to be a little while before I have any boards in hand that are of my own design.  So to scratch my soldering itch I ordered some very cheap kits off eBay a little while ago.  No other motive in mind with these other than just a bit of fun putting them together.  There are kits available locally, but none of them are this cheap.  If they were things I might put to use I'd be happy to spend a little more, but as these will probably just got on my shelf of bits - the cheaper the better.  The first two were through hole clock kits, $5.60 and $7.70 respectively (including postage).   They actually arrived quite quickly.   Kit no. 1:

Both kits have a PDF with schematic and contraction details.  The PDF is not required for construction though thanks to the detail on the silk screen.  Kit no. 2:

Both kits are based on an Atmel AT89C2051, have a buzzer, various alarm/chime functions and buttons with a menu system for settings.  The second kit also has count down and stop watch functions.  No battery backup on either.  The first kit is 5V and comes with a USB power lead, the second is anywhere from 7V to 12V and comes with a short power lead with a plug on one end.

Both went together without issue and worked first go.  Not rocket science at all - but I still enjoyed building them both.

The other purchase I made was some SMD practice kits that were $1 each plus $0.99 postage.  I have done a little bit of SMD work now, but not a lot by any stretch.  I wanted to do a bit more SMD work and this seemed like the cheapest way to do it.  They are purely just practice boards with no function at all:

The quality of the board in these kits is not amazing - but its good enough to practice with.  I bought a few - but have only soldered one so far.  Good practice.

Commodore 128 - Part 1

I bought something off eBay about 2 weeks ago now and it arrived yesterday:

As the title suggests - a Commodore 128.  I've wanted a Commodore 64 or 128 for a long time but they always seemed quite expensive on eBay.  This one is a complete gamble.  Sold as is - untested - due to there being no power supply and video cable to test with.  It was however priced appropriately for a change and in Australia.  So I rolled the dice.  The auction included just the unit itself and a copy of the Commodore 128 System Guide:

The outside cover is a bit poor but the inside pages are like new.  Interesting British stamp printed on the front.  I also found a note inside the guide on a bit of paper about how to load a program from disk.  What was interesting about this hand written note was the paper the note was written on:

Check out that offer expiry!

I have a power supply and video cable en route which I'll put some more info up on when they arrive - as well as seeing whether the unit powers up and works or not.

The first thing I did when this guy arrived was open it up.  To my untrained eyes it looks as though it hasn't been opened since it was built in the mid 80's.  Even the heat grease on the main ICs that touch the large metal shield to act as a heat sink looked original.  Apart from the yellowing of the top half of the case it is in pretty amazing physical condition inside and out.  There was just a little bit of dust on the inside (not bad for a life of just under 30 years).  Nothing a quick clean couldn't fix:

I've got a few other things I'd like to buy/try and build for this guy but am holding off doing anything else until the power supply and video cable arrive to see whether this bad boy works or not.  Fingers crossed!

New Bench Supply

I finally pulled the trigger and bought a bench power supply.  Up until this point I have just been using the ATX breakout board.  I've been looking around for a while, trying to way up price vs features and finally settled on the Siglent SPD3303D.

The supply has 2 fully adjustable channels that can work in independent, series and parallel modes.  The 3rd channel switches between 2.5v/3.3v/5v at 3A.  The display only covers the first 2 channels, the 3rd channel just has the LED displaying CV/CC mode.  The 2 adjustable channels also have a timer function which can be programmed either on the supply itself or via USB using the included software (just like other features).

I settled on this guy because it ticked all my boxes - and physically was the right size for my shelf as well.

There is quite a lengthy thread on this particular supply here on the EEVBlog forum.  This thread mentions two issues found with the supply - namely:

1. Spikes / overshoots on CH3 during power on / power off of the entire supply
2. Spikes when the output of CH3 when a load is removed

If you read the entire thread on the EEVBlog forum you'll notice that both Siglent and the Australian supplier mention that there was a revision of the hardware late last year (2013) which fixed these issues.  As posted by Siglent Support the hardware version number has not changed. The supplier confirmed that the version I had ordered was this latest revision. 

So the first thing I did was some testing when the supply showed up.  The results I got show that there is some level of fix that has been applied to the 3rd channel.  Cold start of the whole unit with a load resistor on the 3rd channel:

There is still a spike there.  Removing the load from the 3rd channel:

Again still a small spike.

Both of these results are less that the original issues picked up with the hardware revision from last year.  And they only occur on the 3rd channel - which I personally don't have a huge issue with.  The first two channels don't have any of these issues. 

I also wanted to note that the service I received from TRIO Test & Measurement was awesome.  If you are in Australia check them out!

Getting started with CPLDs

Just like playing with micros I wanted to get my hands on and play with come CPLDs so I went hunting around for some tutorials.  The one I settled on to start with was this one.  It uses a CPLD from the Altera MAX II family.  The chip itself is not overly important but the branding on the chip is - as this is basically an exercise in learning how to use a the associated vendors software.  I found the same boards used in the tutorial here, ordered and waited for delivery.

Once the boards turned up I opened one up and noticed that the board was not very clean.  There was a lot of extra flux and other gunk on the board.  It worked - it just wasn't clean, so I thought I'd have  go at cleaning it.

After googling around I found a lot of people using a lot of different ways of cleaning their boards.  At lot of people talked about just washing it with some warm soapy water, or even putting it through the dishwasher.  I found this completely weird, I've never thought water and electronics should mix.  Given these boards were so cheap though I thought it would be better to try it with one of these cheap dev boards and kill them than try it for the first time with something else.

So I washed it with some warm soapy water and a toothbrush, and it came up really well.  To make sure it dried out properly I thought I'd put it in the over for a minute.  The oven was off - after just having cooked lunch.  The board was in there for 5 minutes max - this being the result:

The board was dry, but notice the melted power connector and power button below it!  I hooked up my bench supply and shorted the switch and the board still worked!  So I headed down to my local Jaycar store, but unfortunately they had no stock of the DC barrel jacks or the non-momentary switches in the foot print I needed.  So I headed home and got on eBay and ordered some replacements.  While a lot cheaper, I also then had to wait another couple of weeks for the bits to arrive from overseas.  In the meantime I carefully removed the broken components:

The parts finally arrived (I also finally got the lamp for the bench that I'd been chasing):

Now that the board was clean (and complete) I cracked on with the Hackshed tutorials.  Starting with the "Hello world!" of electronics - blinking an LED:

The tutorials are a great way to get up and running with the Altera software very quickly.  I wouldn't say the software is complicated - its just not very intuitive for someone who has't used it before.  Bil Herd over at Hack a Day has started a series on Programable Logic which is also well worth checking out (and not just because it's Bil Herd doing it).

As Bil would say "Keep Hacking!".