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

Review of iFIX RT300M v2 LED tester

In other posts on LED luminaires, I identified the need for a test device for LED strings of up to 200+V at currents up to 280mA.

There are quite a number of competitive devices in the market, the article is a review of the iFIX RT300M v2 (which is also sold under other brand names, they may or may not be sourced from the same factory… the Chinese are copyists).


I purchased one of these devices, and it was faulty on delivery. The output voltage never rises above 0.3V, determined to be a hardware fault. With eBay’s intervention, a full refund was obtained without returning the faulty unit which turned out to be a small blessing later.

The v2 RT300M has a button on the top edge of the device. Continue reading Review of iFIX RT300M v2 LED tester

Adjustable plank refurbishment

I have an adjustable aluminium plank (2.4-3.9m) which after years in the weather, has needed replacement of the plated steel 1/4″ pop rivets used in its construction.

These are strictly for DIY use as long plank spans have not been allowed on work sites for a very long time.

On assurances from the retailer I purchased for $99 a Kincrome CL960 Heavy Duty Hand Riveter Long Arm 525mm (21″) designed for 1/4″ stainless steel poprivets. It failed with less than a dozen rivets with what seems to be a serious design fault (rivet mandrels jam in the inner tube) so it was returned at my cost for a refund. Whilst I have bought lots of Kinchrome product over time, it is when there is a problem one learns a wider lesson.

On assurances from another seller, I then purchased a similar tool on eBay for $36, a tool claimed to work up to 5/16″ stainless steel rivets… so some reserve there?

It failed on the fifth rivet, one of the collets cracked in two and the inside of the chuck sleeve (top right) was grooved suggesting it was not hardened properly. Again, refunded but his time without paying return shipping. Continue reading Adjustable plank refurbishment

STC-1000 firmware change – STC-1000B

STC-1000 firmware change documented a chip and firmware update to a popular Chinese thermostat.

There has been enhanced firmware for a STC-1000 controller based on a PIC chip, but in my experience, most seem to be made with an STM8S003F3 chip. More recently, what appears to be a port of the PIC software to STM8 has been published at

The enhanced firmware is directed at home brewing for control of long running fermentation processes etc, incorporating storage for a number of multi-step programs (profiles). It is not really suited to more general applications like a fridge controller as for example it is more difficult for the common operation to set the set point.

This article describes a similar update to a later model STC-1000. Continue reading STC-1000 firmware change – STC-1000B

Milton Moore’s power supply test

When I was a student at TAFE in 1970, a teacher, Milton Moore, explained why the lab power supplies that were used, Perini & Scott 30V 2A, were the largest power supplies given their modest capability.

He explained that they were almost student proof. He went on the classify students in three categories, the average students constituted the bulk, then there were the quite inept who damaged the best equipment by doing things that no one could have anticipated, and the very bright who sought to understand equipment and expose their weakness.

Milton explained that they tested these power supplies using the rat tail file and hacksaw blade test. One output terminal was attached to the rat tail file and the other to a hacksaw blade, the voltage and current were set to max and the rat tail file and hacksaw blade were rubbed together yielding a shower of sparks… and possibly smoke from the DUT.

At the time I was very interested in overcurrent protection of linear regulators, so this was especially interesting.

ua723 – the darling of power supply designers of the time

Lets look at the issue with the ua723, recently released at that time and appearing in lots of designs.

Above is a schematic from the ua723 datasheet. Rsc is the current sense resistor and it is chosen to develop 0.6V at the current limit, so for instance in a 20A power supply it would have a value of 0.6/20=0.03Ω. So, the current sense circuit presents a Thevenin equivalent circuit of Vth=Rsc*I and Rth=Rsc. Continue reading Milton Moore’s power supply test

Programming a certain type of Chinese 315/433MHz EV1527 compatible remote relay

This article describes the programming sequences for a common Chinese 315/433MHz remote relay which works with the common EV1527 transmitter.

The EV1527 should not be confused with high security protocols, the transmitter has burned into it four fixed supposedly relatively unique codes (in a space of 1 million code possibilities) and sends the burned in code associated with the transmitter key each time it is operated. This should not be confused with rolling code systems such as KeeLoq. This information is not usually disclosed by sellers.

These are usually supplied with little or no instructions, or bad online translations that are quite misleading. I dare say sellers have refunded money in lots of cases due to user confusion about programming them or compatible transmitters. This information might assist owners to find a working solution.

Above is an example remote relay (~$3 on eBay), they are available with a number of channels and may look physically different but use the same or similar firmware. Note that though the relay on this one is rated at 10A AC, that rating is for resistive load and it is rated at 5A AC for an inductive load (PF=0.4). Continue reading Programming a certain type of Chinese 315/433MHz EV1527 compatible remote relay

Reinforcement of nanoVNA-H connectors – performance discussion

At Strength of reinforcement of nanoVNA-H connectors I showed a method I used to reinforce the SMA connectors to reduce the flexing of the PCB when the SMA connectors were torqued to specification for reliable measurement.

This has been commented on by online experts stating that Hugen, the designer of this board, posted notes about his efforts to keep the grounds for tx and rx port circuits isolated to some extent.

Opinion by some is that the modification I performed above which electrically bonds the two connectors through a brass bar of about 60mm length is likely to significantly degrade performance. Continue reading Reinforcement of nanoVNA-H connectors – performance discussion