This article documents the build of an inexpensive regulated power supply available on the Internet for around A$15 posted.
Above is the completed power supply (with some modifications as discussed below). Continue reading An inexpensive Chinese regulated power supply kit.
Generic heating / cooling controller describes a bang-bang type thermostat based on a AtTiny25.
This article works up an example application using a Pt100 RTD sensor. Pt100 is the designation for a platinum (Pt) resistance temperature detector with nominal resistance of 100Ω at 0°. Pt has a nearly linear resistance / temperature characteristic and high accuracy. Continue reading Using a Pt100 RTD with my generic heating / cooling controller
The N2006P is a inexpensive PID controller, typically for heating and cooling operations. There are lots of similar devices for under A$20 on eBay.
Above, the controller in a minimal test harness using a Type K Thermocouple for temperature sensing and 40A SSR mounted on a heatsink. (The SSR output should be protected with an MOV for inductive loads.) 480VAC 40A SSRs sell for as little as A$5 on eBay. Continue reading N2006P PID checkout #1
Some time ago I published a calculator for estimating the impedance of RF inductors on toroidal ferrite cores (Calculate ferrite cored inductor).
The calculator (input form above) use the core dimensions and complex permeability as the basis for calculation.
There are some popular cores that are not simple toroids and so not suitable for direct use with that calculator. For these cores, a practical method is to measure the inductance constant Al (inductance of 1 turn in nH) at low frequency (where µ=µi), and using the µ’,µ” characteristic from the datasheets, to calculate the impedance at the desired frequency. Note that µ’,µ” are usually frequency dependent for ferrite materials. Continue reading A new impedance calculator for RF inductors on ferrite cores
Steve (G3TXQ) posted a graph comparing Cecil’s (W5DXP) measurements of two turns on FT240-52 and FT240-K.
It is interesting to reconcile the #52 curves with Fairrite’s datasheets. A simple reconciliation is to compare results at the frequency where µ’ and µ” curves cross over. Continue reading Attempting to reconcile W5DXP & G3TXQ’s comparison of K and 52 mix ferrites
Jaycar have sold the MP3090 (Manson SPS-9400) over many years. I have one dated 2001 and they are still in their catalog in 2015. Manson is a Chinese manufacturer of medium quality power supplies, at reasonable prices. Continue reading Jaycar MP3090 / Manson SPS-9400 repair
Among forum experts, there are ready recommendations for the ideal ferrite material (or mix) for a balun, often without knowing any detail of the application.
The ‘magic’ mixes include K. Perhaps they are devotees of Sevick.
Over some years I have searched for manufacturer’s data on K mix, and found only two references:
- Amidon who give a very brief table summarising characteristics, inadequate for RF inductor design; and
- Ferronics who give characteristic curves, albeit in less common format.
Problem is that Ferronics µi is 125 against Amidon’s 290… so their K materials are different.
One has hoped that an interested competent person might have made measurements of some samples from Amidon to give full characteristic curves, it isn’t that hard. Continue reading Ferrite K mix
I tested a couple of LM386 audio power amplifier modules.
The larger one was a kit using the DIP package, the smaller came assembled and used a SO package. Both cost less than $2 each posted on eBay.
They both deliver close to 3Vpk into an 8Ω load at 1kHz when powered from 12.0V. That is close to 0.5W out, but the SO chip cannot withstand the associated dissipation of 0.5W continuous output.
Both handle broadcast program quite happily at 0.5W peak, the chip temperature rise is 15° and 25° respectively.
I wrote in the fraud of energy efficient lighting – e-ballasts of frustration with green measures forced on us, measures that have replaced tried and true reliable lighting solutions with high tech low reliability solutions in a false promise of net energy saving.
Typically, the cost of repair and replacement of this unreliable technology is much greater than their direct energy saving, indeed much greater than their energy consumption of the life of the equipment.
Above is a ballast removed from a light this morning after 4 years during which it was hardly ever used… perhaps 10 hours at most… so the original capital cost of $80 for luminaire and fitting for 10 hours service gives an average cost of $8/hr for capital and about $0.01/hr for energy. Continue reading Another Osram e-ballast bites the dust