Category: Electronics

Fair-rite’s ‘new’ #43 permeability data (2020)

Fair-rite publishes spreadsheets of the complex permeability characteristic of many of the ferrite mixes. This note is about #43 mix and clarification I sought from Fair-rite.

Question

I note that recently, the published table of #43 permeability changed subtly but significantly. Does this table apply to historical product, or does it only apply to new product, ie was there an actual change in the mix, or what it the result of better measurement of characteristics?

Continue reading Fair-rite’s ‘new’ #43 permeability data (2020)

Last update: 5th May, 2021, 7:09 AM

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

Last update: 3rd April, 2021, 10:40 AM

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

Last update: 18th February, 2021, 5:20 PM

Mornhinweg ferrite core measurements – #61

Further to Amidon’s method of rating ferrite inductors and transformers, this article discusses some interesting measurements of ferrite toroids by Manfred Mornhinweg (Mornhinweg 2019).

Mornhinweg ferrite core measurements – #31 discussed his measurements of a #31 suppression sleeve.

Above are his measurements of a FB-61-6873 sleeve. Essentially there are two measurements at each frequency, and the expected flux density B is in the ratio of approximately 2:1. He has fitted a straight line on a log/log graph to the measurements at each frequency. The similarity of the slopes is not unexpected, and is a tribute to his experiment design, execution and calculations. Continue reading Mornhinweg ferrite core measurements – #61

Last update: 27th January, 2021, 7:57 AM

Using complex permeability to design with Fair-rite suppression products

Fair-rite allocates some of its closed loop ferrite products to two different categories:

  • inductive; and
  • suppression.

Sometimes the same dimensioned cores are available in both categories with different part numbers and possibly different prices, implying some real difference in behavior, eg 5943003801 and 2643803802 are both FT240-43 sized cores.

Material datasheets often contain a note like this from the #43 datasheet:

Characteristic curves are measured on standard Toroids (18/10/6 mm) at 25°C and 10 kHz unless otherwise indicated. Impedance characteristics are measured on standard shield beads (3.5/1.3/6.0 mm) unless otherwise indicated.

I sought to clarify my interpretation of this clause by asking Fair-rite …whether the published material permeability curves / tables apply to suppression product. Can I use the published permeability curves / tables to predict inductor impedance reliably for suppression products?  Fair-rite’s Michael Arasim advised… Continue reading Using complex permeability to design with Fair-rite suppression products

Last update: 27th January, 2021, 7:33 AM

Calculate ferrite cored inductor – rectangular cross section – enhancement – chamfered corners

The calculator Calculate ferrite cored inductor – rectangular cross section has until now assumed that the toroid has sharp corners. The corner treatment varies across commercial products, some are burnished which removes very little material, some have a chamfer or bevel, some are radiused. All of these treatments give rise to a very small error in calculated ΣA/l.

The calculator has been revised to include 45° chamfers of a specified length on all four corners. If the chamfer angle differs, the error is very small in the range 30-60°. If the corners are radiused, use the radius as the chamfer length, the error is very small. Continue reading Calculate ferrite cored inductor – rectangular cross section – enhancement – chamfered corners

Last update: 28th January, 2021, 3:05 AM

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

Last update: 24th February, 2021, 3:40 PM

Mornhinweg ferrite core measurements – #31

Further to Amidon’s method of rating ferrite inductors and transformers, this article discusses some interesting measurements of ferrite toroids by Manfred Mornhinweg (Mornhinweg 2019).

Above are his measurements of a FB-31-6873 sleeve. Essentially there are two measurements at each frequency, and the expected flux density B is in the ratio of approximately 2:1. He has fitted a straight line on a log/log graph to the measurements at each frequency. The similarity of the slopes is not unexpected, and is a tribute to his experiment design, execution and calculations. Continue reading Mornhinweg ferrite core measurements – #31

Last update: 27th January, 2021, 7:46 AM

Gauss based ferrite core loss

A reader of Amidon’s method of rating ferrite inductors and transformers wrote to support Amidon’s approach and cited a video by W0QE.

W0QE’s video #80: High Power Balun with #31 Ferrite Material gives some measurements and simulations of a FT240-31 inductor with 11 and 14 turns.

In the video he states:

It turns out that the heating effects in the coil are related to the voltage across the coil only, not the current through the it or anything else.

In fact, there is current flowing through the inductor and that develops a voltage difference across the ends. When we are talking about the self inductance properties, then we are talking about the voltage induced in the inductor as a direct result of the current flowing through the inductance.

Let’s look at his own figures to demonstrate,

Above is his Simsmith model. Let us focus on just the left hand two elements L and R1 (for the 11t inductor) as it is a quite complicated model. L was derived from a measurement of the inductor in a fixture, and to some extent the fixture is captured. Continue reading Gauss based ferrite core loss

Last update: 19th January, 2021, 6:57 PM

Amidon’s method of rating ferrite inductors and transformers

I have set out an initial design method for RF inductors and transformers using toroidal ferrite cores and over time I get correspondence drawing my attention to Amidon’s advice, specifically sections 1-35 and 1-36.

Section 1-36 states explicitly that it is applicable to Iron Powder and Ferrite, which is interesting because they are very different materials from a loss point of view.

Basically, their method depends on a maximum safe value for peak flux density.

They give an expression for peak flux density \(B_{max}=\frac{10^8E }{4.44 A_e N F}\) and the following table of design limits for Bmax.

Note that the table and formula are independent of ferrite mix type (though they do mention that “these figures may vary slightly according to the type of material being used.” Continue reading Amidon’s method of rating ferrite inductors and transformers

Last update: 20th January, 2021, 7:35 AM