Time to get some experience with 32bit microcontrollers

After almost 50 years working with 8bit microcomputers and microcontrollers, I thought it about time to get my hands dirty on some 32bit microcontrollers.

The plan is to investigate two streams, one ST Microcontoller based and one ATMEL based, both ARM architecture. Continue reading Time to get some experience with 32bit microcontrollers

Capturing the AVR hex file built by Arduino on Windows

One often sees enquiries by people trying to save the hex file made during the Arduino build process.

It is not trivial, as in their wisdom, Arduino hides these details, and builds the hex file in a randomly named temporary directory for each IDE which it deletes when the IDE is closed.

There are times when you may want to save the hex file, perhaps to load it without a bootloader or using a non-supported bootloader, Flashing LED driver using an ESC was just such a project. Continue reading Capturing the AVR hex file built by Arduino on Windows

Cooling an IC2200H – update #2

I have described a solution an overheating problem with my IC2200H at Cooling an IC2200H.

IC2000HCoolingAnother solution for control of the fan to minimise nuisance draft and noise is one of the inexpensive digital thermostats on eBay.

I reviewed one of these things at Review of inexpensive Chinese thermostat – MH-1210. It had its issues, but as modified for 12VDC operation, I tested it for control of the fan in the above pic.

cctstat01Above is the thermostat, though modified, purchased for about A$12 including post and the sensor thermistor. Don’t buy the MH-1210 as some at least are shipped with incorrect calibration. Continue reading Cooling an IC2200H – update #2

Cooling an IC2200H – update

IC2000HCooling2

I have an IC2200H mounted on my operating table with 25mm clearance above the radio and ample room for convection currents to assist in heat removal. It is concerning that the case temperature reaches temperatures that are not safe to touch, temperatures in excess of 75° (55° above ambient) have been measured and that has not triggered the internal temperature protection… so it could get hotter still!

Whilst it might take a while for the radio to reach high temperatures, in the long term, it must dissipate around 139W when transmitting on HIGH power setting and at ambient temperatures as high as 35° in the shack. (Rated input is 15A at 13.6V for 65W out, leaving 139W of heat to be dissipated.)

This is one of those high power mobile radios that advertises no fan as an advantage, but it is clearly not up to the task!

The objective of this change is to keep the external parts below 60°, the (ASTM standard C1055  1999) 5 second human skin burn threshold.

Continue reading Cooling an IC2200H – update

A test run of the generic heating / cooling controller with 10k NTC thermistor sensor

The generic heating / cooling controller (hcctl) is a flexible bang-bang thermostat controller based on an ATTiny25.

hcctl101

The test load is a pot containing 1l of water and a 1200W immersion element controlled by the SSR above (on-off control). The controller board is a ‘fully optioned’ test framework, hcctl is the left hand DIP8 and the other is a TC427 H bridge (not needed for this SSR which can be driven directly from the ATTiny25 output pin) for buffered output and alarm. Continue reading A test run of the generic heating / cooling controller with 10k NTC thermistor sensor

A test run of the generic heating / cooling controller with Pt100 sensor

The generic heating / cooling controller (hcctl) is a flexible bang-bang thermostat controller based on an ATTiny25.

hcctl101

The test load is a pot containing 1l of water and a 1200W immersion element controlled by the SSR above (on-off control). The controller board is a ‘fully optioned’ test framework, hcctl is the left hand DIP8 and the other is a TC427 H bridge (not needed for this SSR which can be driven directly from the ATTiny25 output pin) for buffered output and alarm. Continue reading A test run of the generic heating / cooling controller with Pt100 sensor

SPI input for the generic heating / cooling controller

The generic heating / cooling controller (hcctl) is a flexible bang-bang thermostat controller based on an ATTiny25.

The project has been expanded to accept a simple SPI temperature sensor. The test case uses a MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter for K type thermocouples. The MAX31855 is around US$5 at Digikey for singles, but the tests were conducted using Adafruit MAX31855.

MAX31855

Thermocouples bring two challenges for hcctl:

  • low noise amplification of very low sensor voltage;
  • compensation of the ‘cold junction’ temperature; and
  • high resolution ADC.

The MAX31855 provides a solution to all of these challenges in a single inexpensive chip. Continue reading SPI input for the generic heating / cooling controller

Adafruit MAX31855 checkout

Intending to enhance my generic heating / cooling controller to read SPI temperature sensors, I purchased an Adafruit MAX31855 module on eBay from a local supplier for about A$26 posted.

The module you might have guessed uses a MAX31855, a Cold-Junction Compensated Thermocouple-to-Digital Converter for K type thermocouple with an SPI interface. The Adafruit module includes a regulator and level translators to use it in a 5V system.

This article describes a simple checkout using a BusPirate V4. Conveniently, the MAX31855 module can be powered from the BusPirate. The thermocouple input is provided by a thermocouple calibrator.

TcCalTest

After a short wait to allow both devices to stabilise at ambient temperature, a test was run. The BusPirate session is as follows. Continue reading Adafruit MAX31855 checkout

LM386 audio power amplifiers

I tested a couple of LM386 audio power amplifier modules.

LM386tThe larger one was a kit using the DIP package, the smaller came assembled and used a SO package. Both cost less than $2 each posted on eBay.

LM386b

They both deliver close to 3Vpk into an 8Ω load at 1kHz when powered from 12.0V. That is close to 0.5W out, but the SO chip cannot withstand the associated dissipation of 0.5W continuous output.

Both handle broadcast program quite happily at 0.5W peak, the chip temperature rise is 15° and 25° respectively.