Atari Portfolio retro computers

Around 12 years ago I had four Atari Portfolio palmtop computers complete with boxes, manuals and a ton of memory cards plus many accessories. For some really stupid reason I decided that they were a pieces of crap and chucked them (I faintly remember trying to sell them on ebay without success) but not before smashing them up for fun.

Well I came across that website I made all those years ago and thought I’d check what they are worth now. Well two sold for over £300 so I really should have kept them as I could have made about a grand out of them. I’ve been clearing out a lot of ‘junk’ recently and it makes me wonder if I should keep it. Who knows what it will be worth in 10 years time?

That’s probably why people hoard things. But I really should not have destroyed those Atari Portfolios…. Here’s some before and after pictures which were taken on a equally 12 year old crappy digital camera.

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NIMH battery tester – firmware version 2. Now with improved voltage reading accuracy.

In my last post I built a multiple AA battery tester but it used the 5V as a voltage reference which wasn’t ideal and was giving readings that were good but could be better. I modified the code to use the 1.1V internal reference of the Mega328 MCU to calculate the actual 5V supply voltage and this has proved to be much better. Voltages measured by the Arduino are now within 10mV when compared with a calibrated DVM.

As far as the battery tester goes this will produce a more accurate mAh rating and a couple of tests show that battery capacity is now within 100mAh instead of the 250mAh as it was before. These measurements were taken at the load resistors as the battery holders and wiring produced a voltage drop between 30 and 110mV which at 550mA load current is fairly acceptable. If you wish to build this project please refer to my previous post as all the build details are in there. I will also put the latest firmware download on the project post as well.

Issues to resolve – spurious voltages displayed when no battery present. Does not affect operation but will look into resolving this.

Arduino NIMH battery tester update

Back in October I posted about a basic NIMH battery tester based on an Arduino nano I made some time back which was a successful project and works quite well however it could only test one battery at a time and didn’t apply a constant current load. It was good but not very accurate and I really wanted the ability to test more than one battery at once.

So looking around for inspiration I saw this Rechargeable battery tester on instructables by Brian Hobbs which can test three batteries at once and displays the test progress and results on a Nokia 5110 type LCD. However the code has some small drawbacks such as using the 5V supply as the reference voltage which isn’t the most accurate as the ‘5V’ supply varies depending on the PSU used and / or the voltage regulator.

Arduino based AA NIMH battery tester

As for other things it does not apply a constant current load either but it does measure the voltage drop across the load & calculates load current from that so it’s much more accurate than my previous project. So far the project has been built hardware wise and is running the original source code with some slight changes to provide indication of test status on a series of LED’s as well as the LCD so test status can be seen from a glance.

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Arduino scrolling clock and custom message on 5×7 matrix


I’ve been playing around with a red 5×7 dot matrix LED display module which I have had in my spares box for a while. I thought about making some sort of scrolling message display as an Arduino project but could not find any more of these modules online as I’d need at least another seven. However I did have an Arduino Nano, a small case with a scratched lid and a piece of veroboard that just happened to fit the box exactly.

I needed to practice my programming skills and after a few attempts of trying to get the display connections right I was able to make some characters appear on the display. It wasn’t anything useful so following a few examples on the internet I ended up with a scrolling message that was hard coded into the program.

Arduino based scrolling message display

Completed messaging display in ABS case

For this to be of any use I needed to be able to upload messages to it so I wrote some code to store the incoming serial data into a buffer then into an array to be displayed. However I couldn’t get it working right; it took ages to transfer the message and every time you wanted to change the message you had to power it off and on again.

It turned out I’d got some of the curly braces in the wrong positions in one of the ‘for’ loops which was causing the delays. I stuffed it into the case (the scratch was on the part which would be cut out for the display window) and then thought, that’s nice and put it in the cupboard and forgot about it.

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Fake DS18B20 sensors from China sold on Ebay / Amazon?

A while ago I read an article on fake electronic components that are flooding the market with high end audio and hobbyist parts being the biggest targets of the fakers. The article in particular spoke about high end transistors used in power amplifiers blowing or producing nowhere near the gain and / or frequency response expected.

It turned out to be cheap transistors packaged and stamped with a high end part number; sure it worked as a transistor but you wouldn’t want to use it in any equipment as it would likely fail. The popular 2N3055 transistor was also a common transistor made by the fakers which turned out to be a small signal transistor die placed in a TO-3 package. It didn’t say where these were purchased from but clearly they had entered the supply chain from the far east.

Do any search on google for fake ICs and transistors on ebay and you will see what I mean. Even microcontrollers have been faked. Yes there are even fabrication plants that copy genuine parts and mass produce them. These chips often will work OK but do have some problems or do not perform as expected.

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Is it even worth repairing consumer goods nowadays?

30 years ago… Yes. Now not so much. Take for example a repair of a Panasonic DMR-BWT720 blu-ray recorder which I was handed for free as it had failed and had been replaced with a newer model. The fault – freezes / runs slow and fails to record sometimes. If it does record the image breaks up. Simple – it’s just bad reception right? No.

To cut a long story short I noticed a lot of noise coming from the HDD mainly repeated ticking sounds. Now with me being an IT professional I knew this sounded like a failing HDD and I know what a knackered HDD sounds like. I whipped the top cover off and removed the HDD and ran some read only tests on it. The drive failed with ‘too many bad sectors encountered’ error as suspected.

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