Solar-powered model planes

[Stumcf]

Hi Mike,
Sorry for slow reply but have just been very busy and have only just seen this post.

The motor is an almost unobtainable AXI2212-34and the prop is an Aeronaut 10x6 or 10x12.

The model has been test glided and works well but I have had a bit of an electronics issue that Martin and I addressed today whilst slope soaring.

Substitution solved the problem but Martin now has my electronics and is going to investigate.

I hope to fly it soon and will let you know how it goes.

Kindest Regards

Stu

[Martin]

I made some new solar controllers, but didn't have any Pro Minis to hand. So I used some of the LGT8F328 boards, which have a few advantages:

• Better voltage regulator that can tolerate up to 20V
• Chip works down to less than 2V, so can tolerate 'brown out' conditions (very unlikely to occur)
• A/D has 12-bit resolution - four times as much as the Atmel chips
• Board is a bit smaller (especially if you use the TSSOP-20 chip version)
• Runs programs faster (32MHz operation, and some instructions take fewer cycles) - doesn't really help for this application
• Cheaper

There are also a few disadvantages - you have to add a 'board' option to your Arduino IDE to cater for the different chip, and if you don't want to use the serial bootloader, you need an SWD/SWC programmer - you can't use a USBasp. If you've used the LGT8F chips before, these aren't really disadvantages - and you can easily make a programmer, using a second LGT8F board.

I've attached the sketch to the O.P. Connection details, recommended resistor values, etc., are in the comments up near the top of the sketch.

[Mike_K]

Just to add what Martin has written, the SWD programmers are also used for programming the STM32 range (and other ARM Cortex controllers, I believe), so they are readily available and cost less than a USBasp.

The common LGT8F328 boards have no crystal, they use an internal oscillator that is not as accurate as an ATmega328P, so they are not so good for use as encoders, as the ppm signal is not accurate (though stable).

Even though they have a 12-bit resolution ADC, the ADC is not as linear and has more noise than an ATmega, so it is arguable if they are better.

They have no EEPROM, but use some of their flash ram as an emulated EEPROM (that then reduces the amount of flash remaining). It uses two banks of flash, and the EEPROM switches between the two, so for 1K emulated EEPROM, you lose 2K flash. Not a big deal for most applications, but it can be limiting for larger sketches.

For the majority of applications, they are a cheaper and faster alternative to ATmega based Arduino. But STM32 blue/black pill boards are usually even faster and cheaper than an LGT8F328 with far more support, so LGT8F328 may not always be the best choice.