Building the XUM1541 USB to IEEE Serial interface

A while ago I repaired a 1541 Disc drive (here), and despite fixing the VIC-20 (here) I hadn't tested the drive. 

I had, however, seen a project called XUM1541 (details are here) which gives us a USB to IEEE serial.... 

So simple! 

An Arduino Pro Micro is pressed into service, but V8 of the firmware resisted many attempts to flash onto my Pro Micro... the webpage described hitting the Reset button just before running the avrdude command line.... but the Pro Micro doesn't have a reset button. I used a pair of tweezers to short out the RST line to GND on the Pro Micro, but still couldn't get it to work ...

After a lot of messing about, what you need to do is plug in your Pro Micro (into a windows machine), and open device manager. Expand on "Ports and LPT" , and you should see your board appear as "Arduino leonardo" .... this is where it goes wrong...  Now short out RST to GND Twice in quick succession. Your board should now appear as "Arduino Leonardo Bootloader" ... note THAT com port number and insert it into the command line. 

Now, short out RST and GND twice again and hit return on the command line within 8 seconds..... bingo! 

All the software and drivers can be found in this handy download https://github.com/r1me/TapeXUM/releases/download/1.0/xum-installer-x64.zip

Once everything is installed, it all works superbly... 

A simple box is printed out.. 

Software works great!

Now , I really need a real C64 to try it all out!

Lamp Limiter / Dim Bulb Tester

One piece of test gear I've never had is a lamp limiter or dim bulb tester. 

They're ideal for s-l-o-w-l-y awakening our vintage electronics up from years of slumber, without too much drama. 

I've been helping my neighbour, Steve, build a pub in his back garden, and while we were testing out some of the electrics, he donated a box of three incandescent 60w lamps to the cause. Ideal. You can't use LED lamps, and halogen lamps are far from ideal.

Here's the schematic.

It's a simple enough circuit. The live side of the mains is supplied via two 60w lamps (in series), each lamp can be switched out as required. This will limit the current and give us a (very) visible sign if there's any issue! 

I purchased a cheap energy monitor from eBay. With both lamps switched out it'll give similar functionality to the Hopi or Killawatt testers. 

I got it from eBay from eBay seller topwoodfly, and it arrived promptly. It has it's own current transformer, as you can see in the picture. 

https://www.ebay.co.uk/itm/394197388411

It's mounted in a box, along with the lamp holders and switches. 

I've put a change over switch on the input to the energy monitor, so we can measure the output voltage. I expect if the output voltage falls too low the energy monitor will stop functioning. I'm not expecting any miracles of accuracy here!

All wired up in a jolly shade of yellow, just to make fault finding on the unit as difficult as possible.

The neutral wire from the mains is passed straight from the input to the output, via the centre of the
current transformer. 

Here's the finished box, running off the bench variac at about 138V

There's a short circuit across the output, just for demonstration purposes!

I must say I'm actually quite impressed by the accuracy of the energy monitor!

Quite a useful addition to the workshop :)