I purchased an inexpensive two channel thermocouple thermometer on eBay. It was very low cost (A$24 inc post) so there was risk that it was low quality and since cost of returns is so high, that it was wasted money.
In fact, it did turn out to have a major problem. Continue reading Dodgy Chinese thermocouple thermometer
The generic heating / cooling controller (hcctl) is a flexible bang-bang thermostat controller based on an ATTiny25.
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 lost soul searching for enlightenment on impedance transformation sought advice on a transformer at 2.4 : 1 BALUN.
Inevitably one of the forum experts counselled:
Assuming your quad is a single-band HF antenna, a conventional transformer using #2 powdered iron would be my choice for the balun function. The reactance of the secondary winding would need to be at least 600 ohms.
So, let’s put the forum expert’s advice to a practical test.
I have at hand a T200-2 core, so lets calculate the secondary turns to satisfy the proposed solution.
Above is calculation from a popular online calculator. For 14MHz, the secondary should be at least 23.8t. We will use 24t. Continue reading 2.4:1 balun design failure
The Neosid 28-053-31 ferrite toroid is used in my HF Balun Project.
This article reports some thermal measurements and analysis made in relation to the project some years ago, but possibly of interest.
Above is the Neosid 28-053-31 ferrite toroid in an implementation of my HF Balun Project using XLPE wire for the winding. The core is a NiZn ferrite toroid of 63x26x19mm (larger than FT240 size). Continue reading Thermal observations on Neosid 28-053-31 ferrite toroid
We often see statements by hams where they draw inference from observed temperature rise of a ferrite core at RF. Lets consider the following statement.
The FT-240-43 balun MUST be quite efficient as it barely increased in temperature over a 5 minute over at 100W on SSB.
For the purpose of this explanation, lets assume barely increased in temperature
means 5° increase in temperature from cold. Under these conditions, we can reasonably assume that almost all of the heat input to the core is consumed in raising the core temperature. Continue reading Interpreting temperature rise in ferrite cored RF transformers and inductors
I mentioned at A walk through of a practical application of AIMuhf/AIM900 that I wasn’t all together happy with feed point R at resonance, at 40Ω it was perhaps a touch high for a 2m quarter wave ground plane on a largish vehicle roof.
Repeated measurement of the DC resistance from the coax plug sheild to car body yielded unstable resistance ranging from 1 to 10Ω. If stable low DC resistance is not achieved, this feed line won’t work properly for RF. Continue reading A walk through of a practical application of AIMuhf/AIM900A #2
Report on Hobbyking 40A ESC 4A UBEC 9261000003 / BC3530-14 brushless drive reported a set of measurements on a test on elements of a drive system which is the basis for one of my flying quads.
This article reports some interesting characteristics derived from the measurements.
Test configuration:
Keep in mind that the application for this drive is a multirotor, and hover speed is around 3800RPM, so efficiency in that region is critical to battery endurance. Continue reading Report on Hobbyking 40A ESC 4A UBEC 9261000003 / BC3540-14 brushless drive #2
This article describes the use of the Array Solutions AIMuhf/AIM900 to test a mobile antenna installation, a quarter wave whip for 2m with about 4m of RG58 cable which has been previously installed and tuned.
The exercise is motivated by a perception that the antenna is not working as well as it should.
Above is a scan of the VSWR. It indicates problems, there should be a main VSWR dip around the high end of the 2m band (147MHz), but instead the minimum is nearer 160MHz. Clearly there is an antenna connected to the far end of the line in some form (ie the inner conductor is not simply broken), but there could be a high resistance in the inner conductor or shield connection (the latter is common issue with this type of antenna base). Continue reading A walk through of a practical application of AIMuhf/AIM900
The generic heating / cooling controller (hcctl) is a flexible bang-bang thermostat controller based on an ATTiny25.
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
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.
Thermocouples bring two challenges for hcctl:
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