A handy 230VAC 15A inline power meter based on an inexpensive module from eBay

This article describes a simple and inexpensive inline power meter for use as a test instrument.

CNC routing

The box cutouts were done on a CNC router, but they could be done with hand tools.

Above, calcs of feeds and speeds for the CNC router. The box is actually ABS, but cutting speed for Polycarbonate is the same.

Above is the tool path for one side of the box. The cutouts suit the 7P-2 strain reliefs. The gcode is generated from a custom Python file using a custom library of common shapes that I use. Continue reading A handy 230VAC 15A inline power meter based on an inexpensive module from eBay

Logging temperature meter (ltm) v1 – prototype Vin calibration

Logging temperature meter (ltm) is a ESP8266 based temperature measurement and logging device.

ESP32

The project is based on port of an existing ESP8266 Arduino project, and consideration was given to migration to the ESP32 hardware platform, but there are large differences to the WiFi related libraries… so for now, ESP8266 looks ok.

A bigger issue is that the ESP32 ADC is renowned for non-linearity, worse in some modes than others.

One poster offered the following graph of an ESP32 measurement to a discussion.

Some developers have worked on a per device look up table to implement a linearisation scheme. That means each individual device needs to have its input characteristic mapped and then used by the compensation code running on that device. Continue reading Logging temperature meter (ltm) v1 – prototype Vin calibration

Logging temperature meter (ltm) v1 – a preview

Logging temperature meter (ltm) is a ESP8266 based temperature measurement and logging device.

The project is based on port of an existing ESP8266 Arduino project, and consideration was given to migration to the ESP32 hardware platform, but there are large differences to the WiFi related libraries… so for now, ESP8266 looks ok. There remain development options for multi channel logging if needed.

Design criteria

The design criteria are:

  • small, portable, battery powered;
  • direct reading temperature scale;
  • flexibility for a range of sensors;
  • local display including bar graph, time, and temperature;
  • log measurements to a serial port of some kind;
  • offer remote access for recent measurement log.

Algorithms

The initial algorithm implemented is for a negative temperature coefficient (NTC) thermistor using the single ADC port on the ESP8266. The code uses the Steinhart-Hart model to solve for temperature.

Above is a plot of the Steinhart-Hart model (red) and the so-called B equation (green) for the NTC used in my car. They are quite similar in this case, but the Steinhart-Hart model is more accurate. Continue reading Logging temperature meter (ltm) v1 – a preview

A handy 230VAC 10A inline power meter based on an inexpensive module from eBay

This article describes a simple and inexpensive inline power meter for use as a test instrument.

CNC routing

The box cutouts were done on a CNC router, but they could be done with hand tools.

Above, calcs of feeds and speeds for the CNC router. The box is actually ABS, but cutting speed for Polycarbonate is the same.

Above is the tool path for one side of the box. The cutouts suit the 7P-2 strain reliefs. The gcode is generated from a custom Python file using a custom library of common shapes that I use. Continue reading A handy 230VAC 10A inline power meter based on an inexpensive module from eBay

A DIY thermostat based on the MS1230A controller

This article documents the build of a DIY thermostat based on an inexpensive ($12) Chinese temperature controller.

Controller module

The controller used is a 220VAC MH1230A.

Above is an internal view of the controller. Importantly it has a relay rated at 240V 30A, and 15A at PF=0.4. The datasheet rates the relay for a 2HP (1.5kW) motor. It uses a ‘conventional’ power supply, the brown component is the power transformer. Most similar products use inadequate relays and have low grade switched mode power supplies that create RF noise. Continue reading A DIY thermostat based on the MS1230A controller

A thermostatically controlled pot for waxing leg hold traps

We periodically have problems with rabbits from an adjoining reserve, and this summer has been bad enough to do something about the crepuscular critters.

Leghold traps from the factory are usually covered in some type of rust resisting oil combined with the residues of the manufacturing processes, all of which needs to be removed to de-scent the traps.

Practice varies, I spray them with ordinary degreaser and then after 5 min jet them clean with water.

There are a range of practices to colour and wax the traps, for rabbits I simply wax them and with supply shortages, I experimented with ordinary soy wax for container candles. This wax does not try hard, so it is not inclined to crack off, and it reduces rusting whilst lubricating moving parts.

Above is a pair of Victor Softcatch #1 traps that have been cleaned, lightly rusted (for colour), cleaned again and waxed. I also use Bridger #1.65 traps which do not rust as easily, so they are used without colouring at all and they seem every bit as successful when covered in sieved soil.

OTS

Above, the 7.6l stainless stock pot from Big W (~$11), a 1100W coil type electric cooker (~$20). Continue reading A thermostatically controlled pot for waxing leg hold traps

Fox flasher MkII update 2/2021

Fox Flasher MkII and several follow on articles described an animal deterrent based on a Chinese 8051 architecture microcontroller, the STC15F104E.

This is an update after several years operation outside, and some in-service modifications to improve performance.

Above is the current version after 18 months in the weather. Continue reading Fox flasher MkII update 2/2021

MH1210A, MH1230A operating instructions

Operation instructions

Press “set” button for 3s get into the procedure menu code mode, display the code “HC”. Press up or down for cyclical selection of parameter code of “HC-CP-LA-HA-PU-CA”.
To enter a code, press the “Set” button, press the up button or the down button to change to the desired data and press “Set” to save and exit;
Control the temperature set: press “Set” button, display blink and it is the default setting. Press up or down to change the data and save automatically. (press on up or down for 2s or more to increase the adjusting speed ) heating control: when the temperature control mode ( code is HC) was H, e.g. the setting control temperature is 28 C , slewing range of temperature is 2 C , when the environment temperature >= setting temperature (28’C), the relay will switch off and stop the output load; when the environment temperature <=setting temperature (28C ) – slewing range of temperature (2 C ) and set “delayed start” before, the reply will switch on and output load again, (if the delayed start function doesn’t need, set the delayed start (code PU) to 0)
refrigeration control: when the temperature control mode (code is HC) was C, e.g. the setting control temperature is 28’C, slewing range of temperature is 2 C, when the environment temperature <=after setting “delayed start” time, the relay will switch on and sart output load.(suggest “delayed start” time to the default setting time to protecting the compressor, please set the (code PU) to) if it doesn’t need). Continue reading MH1210A, MH1230A operating instructions

ESP32 WROOM32 – A possible fix for failure of auto-program facility

Espressif’s esptool has a facility to automatically put the ESP32 into bootloader mode using the DTR and RTS signals of the serial interface.

For whatever reason, it is very unreliable. There are many schematics of knockoffs of Espressif’s original DevKits.

Above is the schematic of one of the larger makers of ESP32 modules, AI-Thinker. The auto-program facility is implemented in the logic gate arrangement at right top of the left top block. Continue reading ESP32 WROOM32 – A possible fix for failure of auto-program facility