For the new tinker system I started on I wanted to add a small bench power supply that is variable from 0 to 12 volts. Since the power supply is mostly intended to power up sensors and modules for Arduino shields and Raspberry Pi hats I slapped together a small supply. I wanted to use a LM317 but I got a ton of LM7812s laying around so I came up with this.
Basically it’s a bunch of junk parts I have laying around. The LM7812 is more of a reference voltage and the LM358 and both BC537s in a Darlington array is doing the work. I might switch out the BC537s for a 2n3055. I still need to add a couple of options such as a power light indicator and a output relay so I can turn the output on and off. Maybe I could get rid of the pot and drive the thing via PWM and control it with the Pi.
These are some helpful things to watch out for when you decide to make your own test equipment to go with your AVR’s and mini programmable computers.
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I sat around thinking of a modern’ish computer system for electronics. There is a bunch of stuff out there and so many ways to go about it. So here is the run down.
Raspberry Pi 2 B with 1GB of ram and 16 or 32GB SD.
Bus Pirate 3.6
7inch LCD with touch screen
Arduino and PICAXE programing capabilities
I already have the keyboard, I just ordered the Bus Pirate and waiting until someone has the Pi 2 in stock. I got a 16GB SD card but if I can I prefer to get a 32GB card. Maybe a cheap Wifi module, however I got a Wifi module I pulled from a broken tablet but it runs off of 3.3v instead of the standard 5v.
When I have to work on something outside I have to end up working on the ground or use a chair as a bench. Well today that is going to change. I got some metal poles that use to be table legs and I have a old coffee table top that use to be my old electronics work bench.
The plan is to mount the legs but have them setup that I can easily take it apart and store in my little storage room that is the size of a shower stall. Also the table top will have some options like mounting my hand router and sawzall that I can mount as a crude bandsaw.
Well tonight my Tinker computer died. The failure was some bad caps on the motherboard. I just finished reinstalling Linux and started to smell that typical smell of a electrolytic cap venting out the magic smoke. As far as I can tell everything else in the system is fine. I was able to turn it off fast enough before things went totally wrong. With a visual inspection I saw two caps had vented near the CPU. Typical 16v 330ouF caps. I could attempt to replace the caps but I don’t have any replacements let alone don’t want to dump cash into a super old computer.
I guess now I can finally break down and buy a Raspberry Pi.
I like obsolete / vintage electronics. They still come into use today for my needs.
I got a Belkin F1B024-E Data Switch and a Sharp printer calculator.
The switch box is made for parallel use but really and truly you can use it for anything that is low voltage and low current. All of the pins to A and B match up with the main I/O port on the box so you can switch USB, serial, I2c and of-course Parallel. All you need is some DB25 male to RJ45 adapters and just slap on a RJ45 connector onto the cable you want such as USB, serial or what ever and it will work just fine. Back in the day I use to have a HD44780 LCD and a Apple DMP with one of these switches.
The calculator is going to the parts bin. Maybe I could do something useful with the printer section and maybe try and tap into the Micro Controller and see if I can reprogram it. The MCU is a Mitsubishi 7480/7481 so maybe I can do something with it. If anything the VFD will be useful.
Well I got my Duinomite Mega last night and hooked it up to my 10inch LCD and Acer Mechanical keyboard. I even tossed in a freshly formatted 1GB MicoSD card with a FAT filesystem. However I ran into issues from the get go and just realized what was wrong.
I was using my bench power supply to power it and on the board it says 9 to 30v. I was using 9.5 volts and you can hear the voltage regulator scream. So I did a test on the drop off point of the voltage and it runs just fine at 5 volts. It wouldn’t read my SD card and even tried another SD card and got the error “Cannot read SD Card”. I did some research and the early boards faced this issue. After updating the firmware and once again Windows is my lest favorite for this I was powering up the board via USB. The board can see the SD card. To clear out the mess on the desk I removed my laptop and some cables and then again power on the board with my bench power supply and sure enough the SD card error came back… Since mt bench power supply has a USB socket for powring USB devices I used that just to rule out if there was something wring with the barrel jack portion of the power supply and sure enough the SD card works.
I don’t know if this is a common issue or I was just unlucky. If anything I would recommend on use USB to power the Duinomite.
Since with the 8-bit computer build I am rebuilding my tinker PC. It currently doesn’t have Serial or Parallel but I ordered a PCI-E Serial/Parallel card that claims to be windows compatible but I don’t care if it is since it will be running Linux. A fresh install of Debian Linux Wheezy 32bit since the system only has 4GB of ram and Jessie hates my video card. Typical single Hard drive and a CD burner for kicks.
It’s no so much the hardware but the software.
For the main GUI I like to use Tilting desktops so Awesome will be my choice. All of the typical Development stuff like GCC, AVR-GCC, G++, Python and so forth will be installed. Symbolic system links to serial, parallel and USB will be created for faster/easier access. gEDA for designing/creating circuits. Arduino IDE as well. For text editing I prefer Sublime Text or for a bare minimal pico/nano, I hate vi/vim.
However there will be a few additional toys added hardware wise. A typical LM317 power supply circuit, It will have it’s own dedicated floating supply. A Bus Pirate 3.6 will be integrated as well.
It will be a nice machine for my electronic tinkering.
I for one don’t like making printed circuit boards so I’m giving Dirt Cheap to make me 10 boards for my 8bit computer project. The PCB file I had wasn’t mine and was made with gEDA. I had to make the Gerber files and label them properly. I was going to try OSH Park but they wanted way too much.
A few tips. Avoid using Eagle files and use Gerber files. From what I have been told it’s easier on the PCB maker since they have to end up converting the .BRD file to a Gerber file let alone some people have issues with Eagle cad files. Also recheck yourself ten times to make sure you have all of the layers/parts to your PCB. Last thing you want to forget is the drill/hole file let alone a layer to a multiple layer board.
This PCB wasn’t created by me but was created by Matt Sarnoff. He has leased the PCB file to the circuit board for his Terminalscope circuit that I am going to build for my 8bit computer project.
Here are pictures Dirt Cheap Dirty Boards gave me as a example after I submitted the files.
I just hope they will come out like that in the end.
Serial and Parallel obsolete? I think not…
Kinda of a rant but helpful tips for getting past USB for simple Serial/Parallel tasks.
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