Saturday, 25 February 2017

First tests of Arduino (copy) Pro Mini, and a few other things

Having been rather tied up with work and other non-electronics activities, I found a moment today to finally try out one of the cheap Chinese copy Arduino Pro Mini controllers. These are 'supposed' to be 3.3v, 8MHz, ATmega328 devices.

Initially, first tests, just for supply voltage, went well - it did indeed operate at 3v, and the regulator did indeed produce 3v from a 12v supply... then 2.8v....2.6....2.4.....1.8..... what the heck?

Of course, it had stopped working by this point! Reconnecting a direct Vcc of 3v brought the device back to life - clearly the regulator, or an associated component, didnt like 12v! Hmmm, curious, but not a major issue (I will report it back to the seller and see what they want to do about it!), as the processor still seemed to be running.

Next step then, after taking the trouble to solder the pins on, was to try and program it. Now to do this I have a CP2102 based USB to TTL board, another Chinese cheapo. The serial board is recognised well by the PC. The only trouble is that it doesnt have a DTR line, but the Pro Mini does!

Copy Arduino Pro Mini 3.3v 8MHz & CP2102 USB to TTL
As it happens, it is possible, with a bit of mucking about, to make it program without the DTR line - its a case of holding the Arduino in Reset (with the button pressed) until the very moment the IDE ends compiling and starts programming. Naturally this is somewhat hit and miss! But nonetheless, we managed to upload a new Blink file, and then replace it with the standard Blink file. One thing noted originally is that for a Delay(5000); command, it seemed to light the LED for around 8sec! Were putting this down to inadvertently programming it as having a 16MHz clock, but it might be a peculiarity of the board!

So this Pro Mini has a failed regulator. It might be that one of the caps nearby isnt rated high enough, and it is that which has failed. I will investigate that another time. Either way, I will be more cautious when testing the 2nd one!

I have ordered another USB to TTL converter, same chip, but this time with the DTR line available!

Whilst on the subject of Arduinos, a steady stream of small parts from the Far East has brought to my shores the RCA/Phono connectors needed for the Dew Heater. This is still sat on my shack shelf waiting for its final components. These consist of the Phonos, plus the extra MOSFET driver cards (im going to make this a 3 port controller). I now have everything BUT the extra MOSFETs!

I have also seen an Arduino based project for a Morse trainer magic-morse-on-arduino which looks interesting. It seems to have very few external parts, so I might knock one up and see how it plays.

Shiny Phonos!
Some of the parts that have arrived are not yet of immediate use, mostly SMT PCBs ready for making up various driver and port expander modules (which also await a supply of solder paste!), but some will allow the finalising of a few tasks. One such packet contains wire loops with a 20mm fuse holder on them
Fuse Loop
Clearly not for use 'as is'! The intention of course is that the loop is cut and spliced into the +Ve line of a power cable. The first project that will get one of these is the U3S beacon. Other parts that have arrived to bolster stocks are mono and stereo 3.5mm jack plugs, 2.1mm DC barrel plugs, and a pair of LiPo battery monitor and alarm modules. I promised Bob M1BBV one of these to go with a nice hefty LiFePo battery he has for SOTA

LiPo etc Battery monitor and low voltage alarm
Ive also obtained a 6-way ceramic switch, with the intention of using one of my recently acquired selection of die cast aluminium boxes to build a HF antenna switch.

On a very positive note, I tested the 24V SMPSU yesterday - and survived! Both myself and the PSU lived through the tests, and so it is now mounted into the Clansman 4Ah battery box. The next steps will be to add the DC side fuse holder, the 12v regulator and switch for the fan, and wire the output.

 It will then get a test on-load whilst monitoring the output on the 'scope to see if any additional filtering is needed. I would be most surprised if it wasnt! But this is another project that is at least nearing completion.

I also have to add my thanks to a few members of the Vintage Radio restoration forum for some items that have come my way. First is Graham, from whom I obtained at very reasonable cost five assorted and unmolested die cast boxes. These will prove very useful, with the largest already being eyed up for a possible transverter!

Next up is Jeremy, G8MLK, who had a very large number of mixed miniature coils to dispose of. I jumped in and took a punt on a bag of 100, which gives me a good experimental stock.

Ten of the coils are 465kHz IF transformers - very useful!. There are also around 20 of a single LC tuned circuit in a can, some interesting possibilities for these are forming in my mind!

Another member also provided me, again at a small but reasonable cost, three old books. Now, these are not in great shape, but they are incredibly interesting! One is a 1931 edition of the Admiralty book of Visual Signals (this is also the one in the worst condition), on the fascinating subject of flag and semaphore codes. The other two are volumes I and II of the 1938 Admiralty guides to Wireless Telegraphy. Published as the Royal Navy, and indeed the Maritime services of the world, were finally phasing out the last of the spark transmitters, it gives a fascinating insight into how the Royal Navy's communications equipment was, and the many remaining esoteric practices, on the verge of the Second World War. It was rather a shock to me to find antenna tuning capacitances still measured in 'Jars'

[1 Jar = aprox. 1.2nF]

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