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App note: Testing inductors at application frequencies

Posted on Sunday, January 22nd, 2017 in app notes by DP | No Comments

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An app note from Coilcraft on inductance and Q parameters which are the important factors of an inductor and how these values are found. Link here (PDF)

The accurate measurement of an inductor has always been more difficult than the measurement of other passive components. The primary difficulty with coil measurements lies in the fact that coil inductance and its efficiency are quite frequency dependent; similarly, coil parasitics (distributed capacitance and core/copper resistive losses) vary dramatically with frequency. The measurement of a coil at the application frequency, so-called “use frequency testing,” is more representative of the basic value of the component in circuit than testing at traditional standard frequencies.

Often, the value of a measurement frequency is specified for measurement convenience alone. If the measurement frequency is not the circuit (or “use”) frequency, the result of testing generally will not yield the same inductance value or display the same efficiency as seen by the intended circuit. Given that recent developments of equipment and methods now allow more flexibility in test frequency selection, inductors should be tested at the actual frequency of use, particularly if tight tolerances are required.

App note: Working voltage ratings applied to inductors

Posted on Sunday, January 22nd, 2017 in app notes by DP | No Comments

Coilcraft’s application note about why there are no voltage ratings specified on inductors. Link here (PDF)

Voltage ratings are often specified for many electronic components, including capacitors, resistors and integrated circuits, but rarely for inductors. This article addresses the reasons why working voltage ratings are not typically published for inductors.

There are challenges to determine voltage ratings for inductors, either by testing or calculation. Inductors do not support dc or low frequency working voltages unless the inductance is high (typically >1 mH). Testing to verify working voltage can be difficult and should be application dependent. The various ways inductors are made, and the stresses of processes like wire bending, make calculating a theoretical voltage rating infeasible.

This article presents these issues to make it easier to choose an inductor most appropriate for the specific application.

Free PCB coupon via Facebook to 2 random commenters

Posted on Friday, January 20th, 2017 in Free PCBs by DP | No Comments

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Every Friday we give away some extra PCBs via Facebook. This post was announced on Facebook, and on Monday we’ll send coupon codes to two random commenters. The coupon code usually go to Facebook ‘Other’ Messages Folder . More PCBs via Twitter on Tuesday and the blog every Sunday. Don’t forget there’s free PCBs three times every week:

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Single tube Lethal Nixie clock

Posted on Friday, January 20th, 2017 in clock by DP | 2 Comments

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Andrew Moser made a lethal nixie tube clock:

Clock 1: Single tube Lethal Nixie clock — you know having all the high voltage lines exposed and un-insulated. Inspiration for this design was from this clock. Unfortunately I built mine right after having surgery. I think the painkillers had something to do with the aesthetics… Anyhow I wasn’t electrocuted while building it under the meds…That’s always a plus!
ATMEGA 328 arduino with a DS1307 RTC for timekeeping. Basically the arduino pulls time from the RTC then updates IO. During this it’s got a time based ISR that: interrupts the code, measures the high voltage, then makes necessary tweaks to the boost converter duty cycle via a proportional controller.

Project info at ReiBot.org.

Check out the video after the break. (more…)

How to make a simple 1 watt audio amplifier (LM386 based)

Posted on Friday, January 20th, 2017 in tutorials by DP | No Comments

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A tutorial on making an LM386 audio amplifier circuit from Afrotechmods:

A tutorial on how to use the popular LM386 class AB audio amplifier IC to build a simple mono 1 watt audio amplifier. It costs less than $3 in parts! There is also a brief discussion of how to use high pass filters to prevent op-amp oscillation and subsequent noise.

More info at Afrotechmods tutorial page.

Check out the video after the break. (more…)

Debugging ARM Cortex-M0+ HardFaults

Posted on Friday, January 20th, 2017 in ARM by DP | No Comments

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Erich Styger has written an article on debugging a hard fault on an ARM Cortex-M0+ device:

To me, one of the most frustrating things working with ARM Cortex-M cores are the hard fault exceptions. I have lost several hours this week debugging and tracking an instance of a hard fault on an ARM Cortex-M0+ device.

More details at MCU on Eclipse homepage.

EMP Jammer build

Posted on Friday, January 20th, 2017 in DIY by DP | 1 Comment

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A how-to on making an EMP jammer from JunezRiyaz, project instructables here:

An electromagnetic pulse (EMP), also sometimes called a transient electromagnetic disturbance, is a short burst of electromagnetic energy. Such a pulse may occur in the form of a radiated electric or magnetic field or conducted electrical current depending on the source. EMP Jammer is a device capable of generating a transient electromagnetic disturbance that radiates outward from its epicenter, disrupting electronic devices.

Check out the video after the break. (more…)

SDR radio breathes life into a 75 year old Marconi CR100

Posted on Thursday, January 19th, 2017 in SDR by DP | No Comments

 

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Jon Hudson over at DesignSpark‎ writes:

This is a belated post of a fun project we did for RS Components. With the upcoming 80th anniversary of the founding of ‘RadioSpares’ – the original name for UK-based RS-Components, and the creation of an “Engineers’ Playground” as a feature of the 2016 Electronica event in Munich, we thought it might be fun to create an exhibit which could celebrate aspects of Radio receivers spanning that whole period. What if we were to take an ancient short wave receiver from the late nineteen thirties with its magnificent construction and rugged controls, and to replace the circuitry with a modern Software Defined Radio from SDRplay? What a great combination that would be! And so the project began.

More details at rs-online.com

LED traffic light

Posted on Wednesday, January 18th, 2017 in AVR, project logs by DP | No Comments

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Domen Ipavec shared his DIY LED traffic light in the project log forum:

Traffic lights are all around us, and they seem simple enough but are they really? Real traffic lights can be a very complicated system because it requires sophisticated control and coordination for smooth and safe traffic.
The traffic light I made is much simpler. My sister works in a kindergarten where kids needed a simple traffic light for when they are riding their bikes on the playground.
The traffic light uses some cheap LEDs from China, a step-up converter and an Atmel attiny841 microcontroller to change the light from red to green at a programmed interval.

More info at Domen Ipavec’s blog.

Via the forum.

Check out the video after the break. (more…)

#FreePCB via Twitter to 2 random RTs

Posted on Tuesday, January 17th, 2017 in Free PCBs by DP | 1 Comment

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Every Tuesday we give away two coupons for the free PCB drawer via Twitter. This post was announced on Twitter, and in 24 hours we’ll send coupon codes to two random retweeters. Don’t forget there’s free PCBs three times a every week:

  • Hate Twitter and Facebook? Free PCB Sunday is the classic PCB giveaway. Catch it every Sunday, right here on the blog
  • Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
  • Facebook PCB Friday. Free PCBs will be your friend for the weekend

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • Check out how we mail PCBs worldwide video.
  • We’ll contact you via Twitter with a coupon code for the PCB drawer.
  • Limit one PCB per address per month please.
  • Like everything else on this site, PCBs are offered without warranty.

We try to stagger free PCB posts so every time zone has a chance to participate, but the best way to see it first is to subscribe to the RSS feed, follow us on Twitter, or like us on Facebook.

A 400W (1kW Peak) 100A electronic load using linear MOSFETs

Posted on Monday, January 16th, 2017 in DIY by DP | No Comments

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Kerry Wong built a 400W/100A electronic load using linear MOSFETs:

 I bought a couple of IXYS linear MOSFETs (IXTK90N25L2) a while ago to test their capabilities when used as electronic load, and the result was quite impressive. So I decided to build another electronic load using both MOSFETs. As you can see in the video towards the end, this electronic load can sink more than 100 Amps of current while dissipating more than 400W continuously and can withstand more than 1kW of power dissipation in pulsed operation mode.

More details at Kerry Wong’s blog.

Check out the video after the break. (more…)

Shirt Pocket Transceiver with the Si5351 and OLED

Posted on Monday, January 16th, 2017 in RF by DP | No Comments

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Pete Juliano’s (N6QW) Shirt Pocket Transceiver with the Si5351 and OLED display:

In 2011 I fulfilled a dream of building a shirt pocket sized QRP SSB transceiver. Well actually I built two of them and the second was a diminutive 2″ X 4″ X 2″. Both used through hole components –so no cheating with SMD. In each case the IF was 4.0152 MHz and employed a crystal switched VXO that essentially gave about 100 kHz on 20M SSB. But it was a VXO and there was not full band coverage. But nevertheless a small miracle (or so I thought) that they both worked! You can see the two versions blow.
But with new technology now available to us my next goal is to fit the larger rig with the Si5351 and an OLED display. Today I made that happen!

Project info at Pete N6QW’s blog.

Check out the video after the break. (more…)

Free PCB Sunday: Pick your PCB

Posted on Sunday, January 15th, 2017 in Free PCBs by DP | 18 Comments

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We go through a lot of prototype PCBs, and end up with lots of extras that we’ll never use. Every Sunday we give away a few PCBs from one of our past or future projects, or a related prototype. Our PCBs are made through Seeed Studio’s Fusion board service. This week two random commenters will get a coupon code for the free PCB drawer tomorrow morning. Pick your own PCB. You get unlimited free PCBs now – finish one and we’ll send you another! Don’t forget there’s free PCBs three times every week:

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App note: Operation evaluation of ultra low ON resistance MOSFET supporting quick charge for 1 cell Lithium ion battery protection

Posted on Sunday, January 15th, 2017 in app notes by DP | No Comments

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ON semiconductor’s application note on faster charging of Lithium Ion batteries with consideration on heat suppression. Link here (PDF)

Currently, because LiB (Lithium Ion Battery) is superior in current density and electromotive force, it becomes mainstream of batteries for mobiles such as smart phone. However, because LiB is weak at over-charge and over-discharge, a control circuit is necessary to be used in combination with LiB. For the purpose of LiB current control, MOSFET is used.

This time, we would like to consider the operation and heat transfer of the CSP (Chip Scale Package) product, which is used for current control, with very small size and ultra-low ON resistance.

App note: Application precautions: Power MOSFET application notes

Posted on Sunday, January 15th, 2017 in app notes by DP | No Comments

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Toshiba’s application note on the things to consider when picking a power MOSFET. Link here (PDF)

This document explains selecting MOSFETs and what we have to consider for designing MOSFET circuit, such as temperature characteristics, effects of wire inductance, parasitic oscillations, avalanche ruggedness, and snubber circuit.

Free PCB coupon via Facebook to 2 random commenters

Posted on Friday, January 13th, 2017 in Free PCBs by DP | No Comments

BP

Every Friday we give away some extra PCBs via Facebook. This post was announced on Facebook, and on Monday we’ll send coupon codes to two random commenters. The coupon code usually go to Facebook ‘Other’ Messages Folder . More PCBs via Twitter on Tuesday and the blog every Sunday. Don’t forget there’s free PCBs three times every week:

(more…)

Building an AT2XTKB (AT to XT) keyboard adapter on prototype board

Posted on Thursday, January 12th, 2017 in DIY by DP | No Comments

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Matt built an AT2XT keyboard adapter on prototype board using an AT to PS/2 keyboard cable.

Project info at Matt’s Tech Pages.

Sony TC-252 reel to reel player restoration

Posted on Thursday, January 12th, 2017 in repair by DP | No Comments

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Dilshan Jayakody has written an article about Sony TC-252 reel to reel player repair:

As a first step of the restoration we remove the LA4440 module attached into that recorder and rewire the player with original wiring layouts. After rewiring we check all the transistors in that player and find-out that the couple of 2SC634 transistors are damaged in that player. Because 2SC634 is not available in the market we replace those damaged transistors with BC548 transistors.
For the front panel potentiometers we use standard 10K and 20K (log) potentiometers available in the market.
To fix motor speed problems we replace 1.5MFD + 0.5MFD multi-section can capacitor with two separate 1.5MFD and 0.5MFD (450V) AC fan capacitors.

More details at Dilshan Jayakody’s blog.

Inside the 74181 ALU chip: die photos and reverse engineering

Posted on Wednesday, January 11th, 2017 in reversed by DP | No Comments

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A detailed die photos and reverse engineering of the 74181 ALU chip by Ken Shirriff:

What’s inside a TTL chip? To find out, I opened up a 74181 ALU chip, took high-resolution die photos, and reverse-engineered the chip.1 Inside I found several types of gates, implemented with interesting circuitry and unusual transistors. The 74181 was a popular chip in the 1970s used to perform calculations in the arithmetic-logic unit (ALU) of minicomputers. It is a moderately complex chip containing about 67 gates and 170 transistors3, implemented using fast and popular TTL (transistor-transistor logic) circuitry.

More details at Ken Shirriff’s blog.

Printed Circuit Board V-Groove cutting machine

Posted on Wednesday, January 11th, 2017 in PCBs by DP | No Comments

This is how V-Grooves are cut into PCBs. V-Grooves are half-cuts into the PCBs that allow them to be snapped apart easily. Minimum V-Groove cut length in generally 8cm due to machine cutting length. V-Grooves must be cut across the entire PCB length, it is not possible to make short internal cuts.

This is from our PCB documentation at DirtyPCBs.com about check it out for more PCB manufacturing details.

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