29 November 2023

Tennis for Two emulator

The secret project that went live on November 17th, 2023, was an emulator of the Tennis-for-Two game from 1958. It has been built for MuPIn - Museo Piemontese dell'Informatica - that held an exhibition of tennis (retro)videogames for the ATP Finals 2023.

Several videogames were on display and could be played, like the original Pong from 1972 up to a Wii.

There was a panel describing what should be the first videogame in history, the Tennis-for-Two developed to let visitors (taxpayers) of a USA laboratory interact with their technology. When I saw it I searched online for a modern emulator, found a 2008 project and I knew I could build it with parts I had at home. 

So who visited the exhibition in the second weekend could play an emulator or Tennis-for-Two on a Tektronix oscilloscope.

Fun fact: people spent most of their visit-play time at Tennis-for-Two and Pong games.

The video above shows one of my tests on my Hameg analog oscilloscope, shot with the smartphone that didn't want to focus on the CRT trace. Please refer to the link above for the circuit diagram and firmware (ATmega168 and up).

19 November 2023

PCB design: unfortunate position for a microcontroller IC

The last PCB I designed includes an ATtiny85 microcontroller. Since it will not need many updates I did not include the ICSP header for reprogramming. The first time I needed to swap out the '85 I realised I forgot to leave some room for pulling the IC from the socket. HAH!

I usually insert a small flat screwdriver under the IC and gently lift it up. In the configuration above it is impossible to get in from the left and just slightly easier from the right paying attention to the resistors.

Lesson learned.



17 November 2023

Teaser 2 - secret project

Second part - of three - of the secret project going live in 4 hours in Torino...


Teaser - secret project

This board is from a secret project that will go live tonight at an exhibition. I realised I could build it last Sunday and I knew I already had everything at home, like a good lot of 4k7 resistors :)

This quick project obviously got highest priority and everything else went into stand-by, like the optical TX/RX and 24 GHz.

Looks like November is the month of self-imposed challenges for me.


01 November 2023

OptoSupply OS5RKA5102P and OS5RKA5111P THT ultrabright LEDs

Lately I am playing with LEDs, trying to build a pair of optical transceivers. The TX side will use some very bright 5 mm red LEDs made by OptoSupply. I chose those with 8° and 15° beamwidth. They are OS5RKA5102P and OS5RKA5111P respectively and they should emit 100'000 mcd each, which is quite impressive, also on your retina if you look straight into them.

For the records, one TX will have 8° LEDs, the second will use 15°.

Besides their weird leg shape that requires a custom footprint (I've done it for KiCad) the problem with these LEDs is that they look very similar and you can easily mix them. So, here is a closeup that helps distinguish which is which.

Close-up picture of narrow beamwidth OptoSupply LEDs.
Left is the 8° OS5RKA5102P, right is the 15° OS5RKA5111P.

Left is the 8° OS5RKA5102P, right is the 15° OS5RKA5111P. Physically the 8° has a narrower body, larger anode area and smaller tab on the anode leg.


LEDs and the bags they came in, to confirm part No.!
LEDs and the bags they came in, to confirm part No.!

While testing the 4x4 array I noticed that one LED was dimmer: a closer inspection confirmed that I had soldered a 15° LED amongst 8°. If they worked with the same current that wouldn't be a bit problem, but it is not the case with these two models.

30 October 2023

KiCad TO-92L footprint for hand soldering

Today I received a small batch of PCBs - THT for hand soldering - and halfway building I had to troubleshoot a short on the input Vcc line.

I had a suspect: the 78L05. Well, not "him", but how I soldered it. While I had plenty of space on the board, I used the TO-92L footprint where pins are very close to each other. If you add a bit of rush, sub-optimal lighting and worsening eyesight (with age), a bridge is almost granted.

KiCad footprint for TO-92L components.
One of the TO-92 footprints available in KiCad.

Next time I will use a wider footprint, nevermind if I have to bend pins. No wonder KiCad has TO-92L_Inline_Wide!



23 October 2023

Polarization of LD1115H vs CDM324

Before popping the HLK LD1115H radars I noticed that I could get a stronger signal when the orientation of the antenna arrays between TX and RX (CDM-324) was 90 degrees apart.

I found that the signal was stronger when the modules were positioned - relative to each other - as shown in the picture below.

This relative position provided strongest signal in the lab environment.
This relative position provided strongest signal in the lab environment.

Before conducting any "long" distance test it is worth checking the effect of "swapping" polarization on one side.