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.



21 October 2023

S 042 P and UAA170 from the cellar

At a local flea market I bought a plastic drawer parts storage cabinet with 25 compartments. Drawers had unsorted components inside, mainly carbon resistors with 1W or more rating. At home I emptied everything so that I could wash it and I found some interesting parts, like:

  • "S 042 P" mixer IC
  • "UAA170" LED driver
  • "TDA1200" FM-IF
  • SGS BFT 56 with extra long legs

Considering the ICs I found in the lot I think the previous owner wanted to build a stereo FM receiver kit from the Italian magazine "Nuova Elettronica" (https://www.adrirobot.it/lx-193-sintonizzatore-fm-con-decoder-stereo/).

When I was a teen I was fascinated by the project of a shortwave receiver using an "S 042 P" IC, that I've never been able to meet in the wild for the following 35 years! I think it was already discontinued or obsolete when the article was printed. I wonder if I could finally build that project now!

In the meantime I might try building a running light with the UAA170 and a 555. It could even be made into a freeform sculpture .

17 October 2023

Overvoltage on HLK LD-1115H - don't

In case you wonder how these radar modules handle overvoltage, the answer is: very bad. I gave 12V to both of my specimen while trying to understand where the 5 MHz modulation was coming from (TX or RX CDM-324 side) and they let out the magic smoke.

I removed both 3V regulators but the 3V line is still shorted to ground. There is a little chance that something else blew before the small 24 GHz chip but I doubt so.

I will check with Mauro if it is worth continuing with these modules since the output power is much lower than CDM-324 or the original Infineon part. We do need the tamed frequency drift these radars offer, but RF power is useful too to get decent "DX" results.

24 GHz QRX.