A range of inexpensive serial to Hitachi style LCD interfaces are becoming available.
This article describes the settings for one sold by eshoppingcity1 (and others) on eBay (about A$6 for 5 inc post at the time of writing but they are getting cheaper). It uses the Philips PCF8574T I2C expander chip which is supported by the user developed Arduino LCD Library V1.2.
I have a little RC-4 temperature logger which has been a really handy device for ensuring that our freezers are cold enough, but no colder.
The RC4 has an internal sensor and is supplied with an external sensor that plugs into a 2.5mm TS jack on the side.
This article explores an alternative sensor that could be embedded in equipment of interest. The sensor is a NTC thermistor.
Firstly, I found that none of the 2.5mm TS plugs I had connected to the RC4 properly, but the T-R of a TRS plug worked reliably.
The display was observed with two 0.1% precision resistors and the thermistor characterised.
Above, it looks like nominally a 110k/B=4200 thermistor… which is a little unusual. 100k thermistors with B=3950 and 4200 are fairly easy to obtain though.
Above is a chart of the error in using the two commonly available thermistors. At low temperatures the 100k/4200 isn’t too bad, around 60° the 100k/3950 is better.
It is a simple matter in Excel to correct readings made with a different thermistor. Here is a VBA function to perform the conversion.
Function temp2temp(ft, ft0, fr0, fb, tt0, tr0, tb) 'function to correct temperature reading to a different thermistor r = Exp((1 / (ft + 273.15) - 1 / (ft0 + 273.15)) * fb) * fr0 temp2temp = 1 / (1 / (tt0 + 273.15) + Log(r / tr0) / tb) - 273.15 End Function
You could squeeze all this into a cell formula if you wished to avoid using a VBA function.
Above is an example measurement run made with a 100k/3950 sensor (Indicated) and the corrected data in brown.
I have evaluated three different series of STC 8051 architecture MCUs, the STC89S52RC, STC15F104E, STC15F204EA.
English documentation is hard to find, and in some cases the translation from Chinese to English is poor and diagram annotations (eg flow charts) are still in Chinese. Continue reading An experience with STC 8051 microcontrollers
Fox flasher MkII described a LED driver for an animal deterrent using a Chinese 8051 architecture microcontroller, the STC15F104E.
Above, the schematic. A very simple circuit with just a handful of electronic components (one capacitor, two resistors, one LDR, one Polyswitch, 4 x LEDs and the MCU). Continue reading Fox flasher MkII #3
Fox flasher MkII described a LED driver for an animal deterrent using a Chinese 8051 architecture microcontroller, the STC15F104E.
Above, the schematic. A very simple circuit with just a handful of electronic components (one capacitor, two resistors, one LDR, one Polyswitch, 4 x LEDs and the MCU). Continue reading Fox flasher MkII #2
The STC15Fx chips use a simple TTL/CMOS async programming interface that is suited to the common USB-RS232(TTL) adapters, some of which are less than A$2 on eBay (CH341 chip).
Above, the completed adapter. Both DIP-8 and DIP-28 are located furthese from the operating lever, and pin 1 towards the operating lever, the same jumper connections are used for both chip sizes for STC15F104E and STC15F204E.
There are two spare Gnd pins next to the black jumper above but hidden from view. They are for grounding jumpers that may be required to enable programming of some ‘bootloader protected’ chips.
The 6 pin male and female headers at lower left accept a USB-RS232 adapter (break out board style or cable) with the common Arduino pinout. The only thing that commits the pinout is the 1µF bypass capacitor between Vcc and Gnd pins and the spare Gnd pins. The USB-RS232 adapter powers the chip being programmed, and it needs to be a 5V adapter.
Alternatively one of the little MAX232 adapter boards could be used with a physical RS232 port, but power will be required.
Flashing LED driver using an ESC described a LED driver for an animal deterrent using a repurposed brushless DC motor electronic speed controller.
This article describes a simpler implementation based on a Chinese 8051 architecture microcontroller, the STC15F104E.
Above, the schematic. A very simple circuit with just a handful of electronic components (one capacitor, two resistors, one LDR, one Polyswitch, 4 x LEDs and the MCU). Continue reading Fox flasher MkII
I wanted to embed some thermistors in battery packs to use them with CBAIV and sought specifications from Westmountain Radio who declined to supply the information.
It is a straight forward matter to measure the resistance of a thermistor immersed in a stable bath of water, and similarly to observe the software response to standard resistors. Continue reading Thermistor for CBAIV
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
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
