Diagnosis of a 9:1 transformer from NanoVNA plot – part 2

Diagnosis of a 9:1 transformer from NanoVNA plot discussed an example measurement of a 9:1 transformer on a binocular ferrite core. These are often recommended for use with Beverage antennas on 160 and 80m bands, and this was the maker’s application. In that article, I hinted that the core might not be #73 as the maker thought, or wished.

This article reports measurements of a 9:1 transformer wound on a Fair-rite 2873000202 (#73) binocular core. The pic above shows the test fixture. Continue reading Diagnosis of a 9:1 transformer from NanoVNA plot – part 2

Last update: 13th October, 2022, 8:23 AM

Diagnosis of a 9:1 transformer from NanoVNA plot

A chap recently posted online a question:

I have added two 1:9 transformer (2T/6T) back to back (high side together) and measured with the nanovna – 2 port measurement, as the binocular core I am not confident BN73 or not.

Also I swiped with one port S11, with one transformer where the high side is terminated with a 470ohm resistor load.

Please advise if it can be used for beverage antenna for 160/80m.

Let’s focus on the second test, and assume that the measurements are valid (and that is often an issue), that the 470Ω resistor is close enough to 450+j0Ω and the connections are short.

Above is his s11 sweep from 1 .5-7MHz.

I suspect this is actually #43 material. Continue reading Diagnosis of a 9:1 transformer from NanoVNA plot

Last update: 11th October, 2022, 4:26 PM

IoT – exploration of LoRaWAN – part 4

My experiments with LoRaWAN were cut short by the announcement that The Things Network (TTN) was to discontinue its V2 network in favour of a new V3. This coincided with Laird’s decision to manufacture region specific versions of its gateway, and all existing equipment was designated US region and would not directly support frequency plans used here in Australia.

After some years there is a solution. Newer firmware for the RG191 supports the more generic Semtech basic forwarder and protocols for TTN to configure the RG191 frequency plan… so it is possible to connect the RG191 to the North American server (instead of the AU server), and configure the gateway in TTN for Australian frequency plans, and it all comes together. Continue reading IoT – exploration of LoRaWAN – part 4

Last update: 1st October, 2022, 6:39 AM

Garden environmental telemetry project – part 1

This is the first in a series of articles describing a simple maker / DIY IoT garden environmental telemetry system. The project is a derivative of IoT water tank telemetry project – part 1, and some of the optional components are as per that project (eg battery / solar power).

Plans are to explore some different kinds of sensors including analog and digital connection types:

  • Pt100 remote from a 4-20mA converter (ie long Pt100 3 wire wiring);
  • Pt100 with co-located 4-20mA converter (ie long 4-20mA loop wiring);
  • MODBUS soil sensor (temperature and humidity).

The measurements of this (get) and an another project (bme280r) are posted to the same Thingspeak channel (https://thingspeak.com/channels/436449 at this time).

Above is a screenshot of the Thingspeak channel. Continue reading Garden environmental telemetry project – part 1

Last update: 23rd October, 2022, 8:02 AM

Digital display for DIY 25W dummy load – part 4

Digital display for DIY 25W dummy load – part 1 described a  digital display for a DIY 25W dummy load / digital wattmeter. The original research tested implementations on an Arduino Nano (ATmega328P) and Arduino Mini Zero (ATSAMD21). Though the Zero appears the better chip (32bits, better ADC resolution etc), the dev board is so noisy (ADC wise) that the Nano produces better results.

Other candidate chips are those of the newer AVR chips, and to that end some ATtiny1614 chips were purchased for trial. Unfortunately I have not seen inexpensive dev boards and the chips are not available in DIP format, these are SOIC14 (SSOP14) 150mils.

Above is the result of this morning’s cooking… three ATtiny1614 chips on DIP style break out boards for prototyping. The chips were soldered in a T962 IR reflow oven. The very long unmasked sections of pad to accommodate different width chips make for a messy looking solder job as the solder runs along the long pads. Continue reading Digital display for DIY 25W dummy load – part 4

Last update: 24th September, 2022, 6:11 AM

CG K/ J/ S/ B to 4-20mA 0-1800 Celsius Thermocouple Converter TC Input 4-20mA Output Head-mounted Temperature Transducer – first impressions

CG K/ J/ S/ B to 4-20mA 0-1800 Celsius Thermocouple Converter TC Input 4-20mA Output Head-mounted Temperature Transducer.

So the concept is that one can program the transducer module for a range of input sensors, and lower and upper limits to the conversion range. Another significant benefit is that it does cold junction compensation (and it does not seem possible to disable it if you wanted).. Continue reading CG K/ J/ S/ B to 4-20mA 0-1800 Celsius Thermocouple Converter TC Input 4-20mA Output Head-mounted Temperature Transducer – first impressions

Last update: 11th September, 2022, 11:06 AM

Setting a torque wrench when using an offset adapter

Sometimes an offset adapter is necessary or convenient on a torque wrench. This calculator calculates the correct torque wrench settings to achieve the desired fastener torque.

The torque wrench is designed to provide a torque indication based on a force applied to the handle and the length about which that force acts to turn a fastener. The calibration may not hold if that geometry is changed by some form of adapter.

An oft cited solution is to set the adapter up at exactly 90° to the long axis of the torque wrench, but that is not always possible or convenient.

For the purposes of this explanation, let’s use the Facom S.234 adapter (above). Continue reading Setting a torque wrench when using an offset adapter

Last update: 7th September, 2022, 4:41 PM

EARU Programmable Thermocouple K J PT100 to 4-20mA Converter TC RTD Input 4-20mA Output Head-mounted Temperature Transducer – first impressions

This article is a review of the EARU Programmable Thermocouple K J PT100 to 4-20mA Converter TC RTD Input 4-20mA Output Head-mounted Temperature Transducer.

So the concept is that one can program the transducer module for a range of input sensors, and lower and upper limits to the conversion range. Another significant benefit is that it does cold junction compensation (and it does not seem possible to disable it if you wanted). The stated cold junction compensation range is narrow at 20-60°, it seems unlikely but bears testing. Continue reading EARU Programmable Thermocouple K J PT100 to 4-20mA Converter TC RTD Input 4-20mA Output Head-mounted Temperature Transducer – first impressions

Last update: 5th September, 2022, 6:38 PM

Karen’s Victa

Karen purchased a Victa lawnmower many years ago, and it has expired.

Victa was Australian, but now owned by Briggs & Stratton. The engine is different to most two stroke small engines, the notable differences are:

  • Victa’s G4 plastic carburettor; and
  • the engine is built “upside down”, the flywheel is underneath (ie on the PTO end), and there is no main crankshaft bearing above the big end, the crankshaft is supported by two bearings below the big end.

This article describes the service work to get the mower into good working order.

First checks / observations

The handle bolts and handwheels don’t work, someone has replaced a cup head bolt with a screw and it does not locate in the tube, so a screwdriver is needed to tighten the handle. The lower bolts are loose and need tightening.

The mower takes a lot of effort to push, the wheels are jammed up with string and stuff binding the bearings.

The blades are beyond service life, chipped and blunt, and the blade carrier and mower base are caked with wet decaying grass clippings.

Fuel tank contaminated with solids and water.

This is an air cooled engine, and the cooling fins and cooling fan were caked with oily grass / dust residue. This leads to higher operating temperature, shorter engine life, and performance problems.

Above, the air filter is filthy and will cause rich running which results in carbon build up in the combustion chamber and blocked muffler. Continue reading Karen’s Victa

Last update: 9th September, 2022, 10:58 AM