The HRD-831 (AKA HDR-831) is a low power mini FM stereo transmitter out of China.
The device appears to have FCC approval under the model HRD-831, but is sold out of China in a configuration that may not have FCC approval. Continue reading HanRongDa HRD-831 FM transmitter – configuration and review
The recent article Soldering iron – temperature control failure gave a plot of V’rms vs conduction angle for a simple full wave phase controlled AC waveform, and I have been asked to explain the derivation.
The phase controlled switch turns on at some delayed time from the zero crossing of the AC waveform, and conducts until the next zero crossing.
With the simplest circuits, there is a practical limit to the achievable stable range of conduction angle, and a minimum of about 50° to a maximum of about 160° is typical.
The RMS voltage is the square root of the mean of the square of the instantaneous voltage. We can write an expression for the normalised RMS voltage as a function of conduction angle θ. Continue reading Normalised RMS voltage of a full wave phase controlled power waveform
I wanted to modify a soldering iron to insert brass threaded inserts into holes drilled in plastic parts, and for this application looked to eBay for an inexpensive temperature controlled soldering iron that could be adjusted down to around 200°.
Well first check was of its temperature when set to 200°.
Ouch, that is a fail. The Chinese cheats have supplied product that does not comply with its description. Continue reading Soldering iron – temperature control failure
This article documents the RF electronic part of a HF current probe project.
The AD8310 module was bought on eBay for about $10. Continue reading AD8310 module for HF current probe
One of the intended applications of the CNC router is to cut openings in metal and plastic enclosure boxes boxes for things like LCD displays, tactile button switches, connectors etc.
First ‘production’ job was a box to contain the grbl_ESP32 gcode interpreter, part of the CNC router if you like.
This module is the grbl_ESP32 box in the block diagram above. Continue reading CNC6040 router project – cut of enclosure for grbl_ESP32
One of the intended applications of the CNC router is to cut openings in Jiffy boxes for things like LCD displays, tactile button switches, connectors etc.
After a lot of testing, it came time to try it on some target work.
Above is a scrap Jiffy box and the milling job is to cut holes for three pushbuttons (tactile momentary switches on a veroboard base with 10mm caps) and the holes for M3 screws and pillars. Continue reading CNC6040 router project – test cut of a Jiffy box
A known issue with the common CNC6040 router and similar devices is very poor calibration / linearity of the spindle motor response to gcode Sx commands.
Above is the system block diagram. The grbl_ESP32 gcode interpeter processes a gcode S (speed) command, converting it to a variable duty cycle PWM waveform on parallel port pin 1. Continue reading CNC6040 router project – spindle speed linearisation – using new grbl_ESP32 feature
A known issue with the common CNC6040 router and similar devices is very poor calibration / linearity of the spindle motor response to gcode Sx commands.
Above is the system block diagram. The grbl_ESP32 gcode interpeter processes a gcode S (speed) command, converting it to a variable duty cycle PWM waveform on parallel port pin 1. Continue reading CNC6040 router project – spindle speed linearisation
OpenLog for TinyTrak described a data logger for APRS NMEA data.
This article shows an innovative inline adapter for adding an Openlog to an existing APRS installation where the GPS is powered with 5V via the DE9 connector.
Above, the adapter comprises a DE9 male and DE9 female connector cabled together as a through connection, and the Openlog is wired into one of the backshells, wrapped in heat shrink tube, and velcro’d to the backshell. Continue reading OpenLog for TinyTrak – inline DE9 adapter
Designing with ferrite binocular cores can be frustrating as there are different formats in which data is provided, and data for different mixes on the same dimensioned cores appear inconsistent.
There are several source of the Al parameter for some common cores, often from resellers rather than manufacturers. Continue reading Designing with binocular ferrite cores – published Al values