1202 ALARM

Thanks to Noel on Freegle, I have a bunch of retro 8-bit computers to play with and repair if necessary. Some cool accessories as well. 

I have a bunch of these little motors recovered from broken printers. They have a neat feedback system built onto the back using a slotted infrared sensor and an encoding wheel. All that needs to be added is a 74LS14 (or equivalent) Schmitt trigger to clean up the pulses coming from the infrared sensor. I modified the motor spindle to take the smallest Lego Technic gear and built a little test rig with a linear actuator type arrangement. The motors can be glued upside-down to a 4x2 stud Lego plate and occupy roughly the same space as a classic Lego Technic 4.5 volt motor. VIDEO -  Lego Robotics Test Rig The motor is driven by a L293NE H-bridge IC with another of the Schmitt inverters used to reduce pin count to just 2 - MotorDirection and MotorSpeed. The code uses an interrupt to count the incoming pulses on a pin and also detects a stall situation by checking if the pulse count has stopped when the motor is supposed to be running. TEST CODE // Lego Robotics Test 002 // G...

A kind Freegle user called Niamh (who owns a lovely bicycle) gave me this awesome retro Pioneer stereo system (YouTube video below).  Pioneer Stereo System The CD tray was a bit temperamental and one of the speakers might have a damaged wire, but nothing too serious and the unit was quickly back in action. I only ever came across Pioneer systems in classic cars so was keen to find out how this one performed. I hooked the stereo up to a heavy pair of speakers I got from Will on Freegle a few weeks ago and have been blown away by the sound quality. Real depth and bass. The tape mechanism and big tilt display are just things of beauty, I think I'm in love!

I was given another Acer C720 Chromebook recently and after taking the back off and removing the write-protect screw I flashed the firmware and installed GalliumOS as I did 2 years ago with the white one. Installation wasn't as slick as last time and I'm leaving the original 16Gb SSD in this one and using Google Drive for cloud storage. It seems to be working well so far.  I gave away my old HP Pavilion G6 ( laptop upgrade ) to a guy starting an OU course now that I have this laptop as well as the updated Intel-based Dell for the workshop. I also repaired this Aiwa Walkman for the lady who gave me the Acer C720. A bad synthetic drive belt was the problem, but this was fixed with a rubber belt cannibalized from an old answering machine. The synthetic belts rot away to a sticky goo that is a pain to clean off even with cellulose thinners. This needs some Wham or Duran Duran! 

A spudger (apparently) is a plastic device for prising open the cases of electronic items to get into them to repair them. You can use a flat-bladed screwdriver, but will probably crack or score the case unless you are both lucky and careful.  I never throw out used toothbrushes because they are invaluable for cleaning and degreasing engine parts (EGR valve on a Skoda Fabia being a personal favourite!). It occurred to me that they would make good spudgers with a bit of, well whittling I'd guess you'd call it. If I'm honest, the inspiration was the classic jailhouse shank actually.  Get your Stanley knife and instead of using it for a thrill-seeker liquor store hold up (putting you in the aforementioned jailhouse), whittle the tops of a couple of old toothbrushes into fine spade ends. Ideal for opening radios, DVD players and especially tablet computers. Free and greener than just chucking them away.

Another damaged portable DVD player I got from a kind lady on Freegle. She said it had been dropped and wouldn't play discs anymore. The unit powered up okay and as luck would have it, can read DVD and DivX files from a USB flash drive. A bit of testing revealed that the main turntable motor was only getting 0.5 volts instead of 6 volts and the drive transistor was probably blown. My guess is that when the unit was dropped something jammed the spindle and the stall current blew the transistor.  Anyway, my eyesight isn't up to even trying to replace a surface mount transistor so I thought, why not gut the DVD parts out of this thing and just keep it as a digital player.  And below you can see Chun Yu Fat in the classic action film 'Hardboiled'  playing from DVD files copied on to a USB flash drive. A 32Gb flash drive will hold around 45 DivX film files, plenty of choice.

Upcycled VFD Display Counter Test (Arduino) (YouTube video)  All parts are recycled or recovered from obsolete electronics, with the exception of the Arduino board.  The VFD is being driven by 2 ULN2308 transistor arrays via 10K pull-up resistors to 12volts. There are a total of 16 lines, 6 for digits and 10 for segments. Normally the VFD elements are held high (ON) , but switching a ULN2308 transistor ON pulls the line to GND and turns the VFD segment (or digit) OFF, so inverted logic.  The 2volts for the VFD filament is coming from the Arduino 5volt line via a 10R resistor. The code is based on the Arduino SevenSeg library but I will be writing my own code with interrupt-driven multiplexing for the VFD digits.