Assembled and boxed Clone PI AVR metal detector

Some more photos of boxed Clone PI AVR metal detector and self made coil.

I have made a coil from Ethernet cable between two round plywood sheets filled with Makroflex sealant. More about making coil from Ethernet cable can be fount here. Idea how to seal everything came from here.

Clone PI AVR intself was boxed in a box I bought in local electronics store. I decided to add a switch to switch off external beeper so that sound will be provided only through headphone socket. For the coil connector I have selected some two pin microphone connector. I think in general it came up pretty well.

Will be mounting everything on appropriately bent and painted PVC pipe. Will post pictures later. Some day. Probably.

Clone PI AVR back panel
Clone PI AVR back panel ( external sound on/off, coil and power switch )
Clone PI AVR front panel ( buzzer hole, headphone socket, lcd and controll buttons )
Clone PI AVR front panel
Clone PI AVR internal layout with batteries
Clone PI AVR internal layout
Self made detector coil for Clone PI AVR

Cleaning and repairing ZX Spectrum +3

Got a somewhat cheap ZX Spectrum +3 to my collection. It was marked as untested in eBay ( they usually are ), but I took the risk and bought as the price was ok.  On first test it powered up, the floppy disk was providing sound, TV could be tuned and startup menu appeared. First noticed that some of the keys ( lower part ) were not working. My guess would be that membrane will have to be replaced but anyway, disassembly will show. And it showed. As it more or less was obvious from outside inspection – inside was dirty as hell.

Then, after some cleaning:

I have no CF-2 floppy diskettes to test, so decided to plug in a tape recorder and test some software from and audio cassettes and the i noticed.. that audio jack was missing! It seems that it was just cut away! Found similar one in one my spare parts box and soldered that in.

Also decided that as soldering iron is hot anyway why I would not just make a quick composite mod in the UHF box (using a capacitor). Did that, reassembled it, plugged it in and… yeah – no video.

So, I have undone composite mod, restored everything to original condition and started making RGB to SCART cable for it.

How to build a hardware startup

Some good readings about hardware startups and starting a hardware business:

How To Build A Hardware Startup, Created by Marc Barros

(local copy of paper)

“It’s a simple question: Why are you starting a company?
It’s hard to answer. Either because you don’t know or you are embarrassed about how simple the reason is.
The good news is you can get away without have a clear why for a very long time. Most people will never ask you, instead they will focus on what you have built.

The bad news is down the road then the deck is stacked against you, when you are exhausted from the journey, and when you are wavering between a crappy and a really crappy decision, not having a clear why make you a leader without a compass.”

Eachine H8 Mini silent mod

I was annoyed with Eachines H8 Mine constant beeping in headless mode so decided to make it silent once and for all. This mod is easy – just open the transmitter, remove beeper by desoldering it and solder similar LED instead of it ( check the polarity – positive is marked on the PCB  ). Then drill a hole of LED diameter in front side of controller case and it is done.

Eachine H8 Mini - beeper removed and led soldered instead of it
Eachine H8 Mini – beeper removed and led soldered instead of it
Eachine H8 Mini controller reassembled. You can see old beeper that was removed and new led in its new hole.
Eachine H8 Mini controller reassembled. You can see old beeper that was removed and new led in its new hole.


How to use Arduino IDE to program NodeMCU

1. Install the Arduino IDE from download section of website 
2. Run Arduino IDE’s arduino.exe
3. Arduino IDE >> File >> Preferences (Shourtcut is CTRL + COMMA)>> Settings tab >> on Additional Board Manager URL side type this >> and click ok.

This json object will bring necessary drivers for NodeMCU from the website to our Arduino IDE.
4. Arduino IDE >> Tools >> Board >> Boards Manager… >> Type = Contributed >> click on install (Or, search ESP8266 from the search bar)
5. Arduino IDE >> Tools >> Board >> NodeMCU 1.0 (ESP-12E MODULE)

Repairing ZX Spectrum Kempston joystick

As recently I started tinkering with ZX Spectrum hardware, tested one old joystick I had. Up and right positions did not work during the games. Tested port reading with one simple program:

10 LET x=IN 31
30 GOTO 10

There was no reading in up and right position.
I took apart joystick case and tested connection between PCB and plug – there was no connection for up and right wires.

So, just took now DB9 female connector and soldered it instead of an old one that I have just cut away.


Fixing ZX Spectrum+ 48K (s/n S01-135100) video problems

So, this ZX spectrum was alive, but during testing with some games (for example game “Breakthrough”), I noticed strange video glitch in upper screen part:

My guess was it is not video RAM related, but probably RF module fault. First decided to change all electrolytic caps on the board and see if it helps – it did not. Picture was the same.

Then decided to check RF module – remove it and re solder all joints.

After putting it back I did a check with the same game. It helped a bit, but still I was not happy with the result. White line disappeared, but it seemed like upper part was washed away a bit:

And then it came to my mind a thought about why the hell I am using this RF module at all. I could just do a composite mod and that would definitely would solve all RF related video problems.

Composite mod as it is called, is just disconnecting power and signal wires that go from RF module – means disconnecting RF module. Then, in the RF module itself, disconnecting resistor from video output connector. And finally, connecting video output from board to video output connector in RF module using 100uF 10v electrolytic capacitor ( negative to the board, positive to video output ).

That`s it, did those changes, connected to TV`s composite video input and got clear picture without any RF glitches.

( Making this change i did not cut any wires etc. Just desoldered and moved away. Idea is that I could easily return RF module functionality i.e. undo this mod. )