Driving 14-segment displays with the MAX6954

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App note from Maxim on using the MAX6954 to drive 14-segment monocolor LEDs, (PDF):

This article is how-to guide, intended as a quick learning aid for engineers considering using the MAX6954 to drive 14-segment monocolor LEDs.

The MAX6954 is a versatile display driver, capable of controlling a mix of discrete, 7-segment, 14-segment, and 16-segment LED displays through a serial interface. This application note shows a typical application and configuration for driving eight mono-color, 14-segment LEDs.
See the MAX6954 data sheet for additional information about MAX6954 features.

Driving 14-segment displays with the MAX6954 – [Link]

Cheap Arduino Serial Terminal

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Peter Scargill writes,

As it happens I’m experimenting on a 1284 chip which while being Arduino-compatible kind of, it does have another serial port, so without disconnecting my FTDI – I hooked up the second serial port to the home control serial and fired the DEBUG command at the latter.
As you can see on the left, a perfectly usable terminal. At this point despite YEARS of VT-100 wilderness I’d mastered the colours and scrolling area controls – thanks to this handy VT-100-related link. Not all of the commands work and in order to make a character counter I had to do a custom colour save.”

Cheap Arduino Serial Terminal – [Link]

Using A Bench Power Supply To Charge Lithium Ion Batteries

David Jones has another useful video tutorial about how to safely charge Lithium Ion and Lithium Polymer batteries with a bench power supply. The purpose of this tutorial is to learn how to use your lab power supply to charge your Lithium Ion battery when you don’t have a special charger circuit to do so.

NCR18650BBattery

He used NCR18650B in his tutorial, a 3.6V 3400mAh Lithium Ion battery from Panasonic.
David warned us that charging this type of battery is quite dangerous if we didn’t do it in the correct way. Even with the presence of protection circuit in Lithium Ion battery.

LiionProtec

You can find the charging diagram in NCR18650B battery datasheet.

NCR18650BChargingdiag

According to the datasheet, the charging current is 1625mA and the charging voltage is 4.2V. Charging consists of two stages, first one is the constant current stage where you must supply a 1625mA constant current and when the battery voltage reaches 4.20V, the second stage starts, which is the constant voltage stage. In this stage, the current will naturally drop down, and the cutoff is typically about 10% of charging current so it’s about 170mA.
This tutorial applies to all Lithium Ion and Lithium Polymer batteries not only NCR18650B.

LiIonBatteries

You can perform this 2-stage charging using your power supply, but it must supports CC(Constant Current) and CV(Constant Voltage) modes. You can read the following Q&A in electronics.stackexchange to learn what constant current and voltage modes mean. You can build a power supply with CC and CV modes for yourself if you don’t have a budget to buy a ready made one.

David’s Power Supply Setting With 4.2V CV and 1700mA CC
David’s Power Supply Setting With 4.2V CV and 1700mA CC
The Battery Charges in The First CC Stage Sinking 1698mA
The Battery Charges in The First CC Stage Sinking 1698mA

David said that using this type of float charging/trickle charging is not recommended, because it will build-up or plate the metallic parts inside the battery. So It’s better to use dedicated ICs designed for the float charging.

David mentioned in his video that a complete tutorial is available for whom who want to know in details how to charge lithium ion battery.

 

Exploring Eagle CAD ULPs #2 – ‘Unrouted.ULP’ Zoom To The Last Left unrouted Wire

Welcome to the second post of the “Exploring Eagle CAD ULPs” series. Every week we will publish a new post about one useful ULP in Eagle CAD.

“ULP” User Language Program is a plain text file which is written in a C­-like syntax and can be used to access the EAGLE data structures and to create a wide variety of output files. You can consider it like a plug-in for Eagle.

You can reach the posts published in this series using the following link.

ULPSerPost2

In this post we will discover “Unrouted.ULP” by Daniel Mack. The job of this ULP is to zoom to the first unrouted wire in the board editor. This might be helpful when searching for tiny leftover air wires especially in big boards.
When we use ‘ratsnest in layout editor, a result with remaining airwires is shown in the bottom of the editor. Sometimes airwires are not visible to our eyes and need a lot of searching.

One Airewire Is Left - See the red circle
One Airewire Is Left – See the red circle

“Unrouted.ULP” can zoom to unrouted line and solve this problem for us.

You can see this ULP in action in the below GIF

unroutedulp

You can download the ULP from here: Unrouted_ULP

That’s all for this time, see you next post in this series!

Tools for the Electronics Hobbyist Part 1- Graphical Components Tester

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When I started to deal with Chinese electronics suppliers from websites like Alibaba, Aliexpress and Taobao, I discovered that there are huge amount of undiscovered tools from the Chinese market. They are not easily discovered, maybe due to the Chinese language barrier, especially when we deal with a Chinese website like Taobao or maybe because most of us are used to deal with known electronics distributors like Sparkfun.

I also discovered that I can get my stuff from there in a lower price and in most cases of the same quality.
We can’t deny that dealing with known and trusted electronics stores such as Sparkfun and Adafruit is more comfortable and safe, but our proposal is an alternative one.

That doesn’t mean that our series will focus only on tools from Chinese suppliers. We will also explore special tools from Ebay, Tindie and other resources.

This series is weekly, so stay tuned! Please note that when we talk about a tool from a certain store or a supplier, we don’t claim that we guarantee the quality and if the store is trustworthy.

You can reach the posts published in this series using the following link.

tools_series_1

Welcome to the first post of our series “Tools for the Electronics Hobbyist”. We are going to talk about graphical components tester, which I found on “91make” store on Taobao and it seems that they’re specialists in graphical components testers.

This tool is used to discover the type and main features (like value and some other electrical characteristics) of the majority of discrete components like transistors, diodes, resistors, capacitors and other components.

This is useful when you have an unknown part. As you know a part with TO-220 package can be a BJT, a MOSFET or maybe something else. It is also useful when you know the basic function of the part in your hand and you need to know some of its characteristics.

PartsGraphicalTester

Features:

  • Can used with npn and pnp transistors, n-channel and p-channel mosfet, diodes (including double diodes), thyristors, transistors, resistors, capacitors and other components.
  • Measuring the gate threshold voltage and gate capacitance of MOSFET.
  • Amplification factor (gain) of the BJT and the base of the forward bias voltage.
  • Getting the pinout of the component.
  • Use 9v battery for power supply.

I found a video on Youtube for the same tool tested with a lot of components

It’s available for 40 RMB which is about 6$, and you can see that it’s cheaper than Ebay or Tindie suppliers. You can also read the Hackaday review about this tool.

That’s all for this time , see you on next post.

OEMsecrets.com – Electronic Component Suppliers Price Comparison Search Engine

oemsecrets

There are a number of electronic component search engines in the industry, but finding the best price can often be time intensive. Quite often purchasers are simply looking to locate the most competitive price from suppliers and fast!

OEMsecrets has launched the first price comparison search engine in the electronics market.  The UK shopping site helps you to find the best prices and compare inventory availability from dozens of the industry’s largest authorised distributors. By entering a manufacturer part number, buyers can save both time and money when searching to purchase electronic components online. OEMsecrets compares prices on over 15 million electronic component products from suppliers such as Digikey, Mouser, Avnet, Arrow, Farnell, TTI, Buerklin and many more. Suppliers are categorised into authorised and non-authorised divisions for ease of use.

Buyers are able enter a quantity to find the total cost of the product, change currency and filter by region. ‘Buy Now’ links can be clicked, which sends users directly into the shopping cart of distributors ready to order. Datasheets, reference designs, images and samples from suppliers such as Texas Instruments to confirm product specifications are also accessible on the search results page. Compare prices of part number OPA333AID as an example.

The shopping site is also close to launching a price comparison BOM tool which auto selects the best prices from suppliers for hundreds of line items on a components list from authorised distributors.

For those buyers looking to save time locating components and finding the best price online, take a look at OEMsecrets.com

Hall sensors consume no more than 1.6 mA

Infineon TLx

Comprising both switch and latch types, the TLx496x series of Hall sensors from Infineon offers precise switching points, stable operation, and low power consumption. At 1.6 mA, the devices consume 50% less power than comparable products, and the 5-V versions consume just 1.4 mA. by @ Susan Nordyk @ edn.com:

All of the TLx496x series sensors integrate a Hall element, voltage regulator, choppers, oscillator, and output driver, reducing both board space and system costs. The voltage regulator powers the Hall element and active circuits. The chopper ensures that the temperature remains stable and minimizes the effects of process fluctuations.

Hall sensors consume no more than 1.6 mA – [Link]

Photovoltaic simulator system adds automated MPPT Efficiency Test

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An added test facility enables test of a 1,500V photovoltaic (solar energy) inverter’s static and dynamic maximum peak power tracking (MPPT) according to European Standard EN50530, with a single command, creating downloadable photovoltaic I-V curves, plus static and dynamic EN50530 test reports. by Graham Prophet @ www.edn-europe.com

Photovoltaic simulator system adds automated MPPT Efficiency Test – [Link]

Touch Weather Station using a DHT22 Sensor and a Raspberry Pi 3 with TKInter

educ8s.tv tests the new Raspberry Pi 3 board, by building a simple but useful project.

A few months back, the Raspberry Pi 3 board was released. It is a great new board because it now offers WiFi and Bluetooth connectivity out of the box! It uses a quad core processor which operates at 1.2Ghz and it has 1GB of RAM available. From the benchmarks I have seen, this board is at least 3 times faster than the original Raspberry Pi. It can run Linux and offers 40 GPIO pins for our projects. The impressive thing is its price. It costs around 40$ and Gearbest.com was kind enough to send me a sample unit in order to test it and build projects with it.

Touch Weather Station using a DHT22 Sensor and a Raspberry Pi 3 with TKInter [Link]