App note: Driving multiple loads with 32 kHz Nano-Power MEMS oscillators

Accomodating multiple loads from a single oscillator output discussed in this app note from SiTime. Link here (PDF)

Optimizing board space and managing power consumption of wearable devices is critical in sustaining competitiveness within this fast growing consumer segment. With less power consumed, battery life is extended or provides the option to reduce the battery size. MEMSbased reference clocks offer an alternate to traditional quartz crystal timekeeping components, with advantages including a significant footprint reduction, improved accuracy, and lower system power. In addition, the capability to drive multiple loads with one ultra-small, nano-power oscillator is one way in which MEMS are supporting these improvements.

App note: Tilt-Sensing with Kionix MEMS accelerometers

Kionix low-g acceloreometers used as tilt-sensor. Link here (PDF)

Accelerometers have countless potential tilt-sense applications in today’s motion-enabled world. Tilt-sensing opportunities exist in a variety of industries, such as automotive, consumer electronics and military/aerospace, and include:
• Vehicle stability systems
• Inclinometers
• Cell phone/PDA screen navigation
• Motion-enabled game play
• Tilt-enabled computer mouse/pointer
• Tilt-compensated electronic compass
Some of these applications currently utilize dual-axis accelerometers that, at times, are adequate for the job. A tri-axis accelerometer, however, can enable additional functionality, accuracy and precision.

Inside the Am2901: AMD’s 1970s bit-slice processor

Ken posted an article taking a closer look at AMD’s Am2901 chip:

You’re probably familiar with modern processors made by Advanced Micro Devices. But AMD’s processors go back to 1975, when AMD introduced the Am2901. This chip was a type of processor called a bit-slice processor: each chip processed just 4 bits, but multiple chips were combined to produce a larger word size. This approach was used in the 1970s and 1980s to create a 16-bit, 36-bit, or 64-bit processor (for example), when the whole processor couldn’t fit on a single fast chip.

See the full details on Ken Shirriff’s blog.

Experimental motor driver for CG-4 German equatorial mounts

Dilshan has published a new build:

This is an experimental stepper motor driver for Celestron CG-4 German equatorial mounts. This unit is functionally equivalent to the Celestron dual-axis motor driver, and we developed it as a replacement unit for the original Celestron driver.

See the full post on Dilshan Jayakody’s blog. Project files are available on GitHub.

Building a 12V DC MagSafe charger

Steve blogged about his 12V DC MagSafe charger built:

Now that I have a solar-powered 12V battery, how can I charge my laptop from it? An inverter would seem absurdly inefficient, converting from 12V DC to 110V AC just so I can connect my Apple charger and convert back to DC. It would work, but surely there’s some way to skip the cumbersome inverter and charge a MacBook Pro directly from DC? Newer Macs feature USB Type C power delivery, a common standard with readily available 12V DC chargers designed for automotive use. But my mid-2014 MBP uses Apple’s proprietary MagSafe 2 charging connector. In their infinite wisdom, Apple has never built a 12V DC automotive MagSafe 2 charger – only AC wall chargers. There are some questionable-looking 3rd-party solutions available, but I’d rather build my own.

More details at bigmessowires.com.

#FreePCB via Twitter to 2 random RTs

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.



Non-destructive testing of fuses

Kerry Wong discussed how to accurately determine a fuse’s current capacity non-destructively:

A fuse is a sacrificial device for the protection the rest of the circuit in an over-current situation. There are situations we need to know with some reasonable confidence what the actual maximum current is for a given fuse without destroying it. This is beneficial when the specifications for the fuse at hand is unknown (e.g. with cheap no-name brand fuse), or the circuitry to be protected is so critical that the interrupt current level must be specified precisely.
Obviously for resettable fuses (such as PPTC fuse or polymetric PTC fuse), the rated current can be easily tested repetitively. Thus the focus here is for glass fuses and HRC fuses.

More details on Kerry Wong’s blog.

Check out the video after the break.

Continue reading “Non-destructive testing of fuses”

App note: Addressing floating inputs in digital systems (Bus Hold)

White paper from Nexperia about their bus hold tech. Link here (PDF)

In the normal operations of a digital system, the input to any digital device within is clearly defined – it is either one or zero. There are however interface cases where outputs may be disabled that can result in floating inputs.

High-voltage FLASH programming on ATTINY85

ATTINY85 High-Voltage Flash programmer @ td0g.ca:

The Atmel ATTINY85 is a great chip (cheap, easy to use, supported in the Arduino IDE). Unfortunately it only has 5 IO pins, which limits its usability. There are guides on using a High-Voltage Programmer (HVP) to change the Reset pin into an IO pin. However, that prevents you from programming the Flash (Program Memory) until you re-enable the Reset pin.
Thankfully the Flash can be programmed with an HVP, but the commands and protocol are different. My USBtinyISP simply cannot be modified to be an HVP. Using an Arduino as ISP (In-Service Programmer) on an ATTINY85 is fairly simple but doesn’t work if the Reset pin is disabled.

More details at td0g.ca. Project files available on GitHub.

Mechanical 7 segment display clock using an Arduino & 28 servos

Michael shows us how to build a mechanical 7 segment display clock using an Arduino and 28 servos:

I built a countdown timer a couple of months ago using a two digit mechanical 7 segment display which was driven by 14 servos and an Arduino Mega. It came out quite well and a number of people suggested doubling up on the display to build a clock. The only problem was that the Arduino was already running short on PWM IO and I needed to double up on the outputs. Fortunately, someone pointed me in the direction of these PCA9685 16 channel PWM drivers, so I used them and a DS1302 real time clock module to build a mechanical 7 segment display clock which uses 28 servos and is now driven using an Arduino Uno.

Project details at the-diy-life.com.

Check out the video after the break.

Continue reading “Mechanical 7 segment display clock using an Arduino & 28 servos”

Building a pulse oximeter

John Keefe made this DIY pulse oximeters, that is available on Github:

The heart (ha) of the project is the Pulse Oximeter and Heart Rate Sensor, which includes the sensor itself, a tiny brain to make the measurement calculations, and two “Qwiic” connections. Qwiic is Sparkfun’s system of making it easier to wire up sensors. So I also bought a little box of Qwiic wires.
I’d also need a microcontroller, a credit card-sized hobby computer, to run the show. Sparkfun makes its own version of an Arduino called a RedBoard that is Qwiic-friendly, and that’s probably the easiest option for anyone starting from scratch.

See project details at johnkeefe.net.

An Isolated RS-422 / RS-485 Shield for the Automation Direct P1AM-100 Open-Source PLC

Glen @ bikerglen.com writes:

The RS-422 / RS-485 shield is an open source shield designed to add RS-422 and RS-485 communication capabilities to the ProductivityOpen family of open-source programmable logic controllers (PLC’s) from Automation Direct. It’s loosely based on the Arduino MKR RS-485 shield but updated to use an ADM2582E 3.3 V isolated RS-485 transceiver from Analog Devices. The completed shield fits inside the P1AM-PROTO prototyping enclosure.
If you’re not familiar with the expansion capabilities of the Automation Direct P1AM-100 Open-Source PLC, now would be a good time to read my previous blog post on the subject. For this project, I’m going to create a new design using the Eagle PCB library symbol created in that post then add an isolated RS-422 / RS-485 transceiver and its support circuitry.

More details at bikerglen.com. Project’s hardware and software design files are available on Github.

#FreePCB via Twitter to 2 random RTs

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.

Deconstructing Sega’s System 16 security – part 2

Sega’s FD1089 security module reverse engineering part 2:

The FD1089 module variants from Hitachi / SEGA were fabricated in a plastic case, on the back of the module a epoxy layer is visible together with two rows of pins arranged as DIP64. This arrangement mimics a standard 68000 CPU as intended by SEGA.
The sample shown below features the SEGA code 317-0013, this indicates the module was used as part of a Enduro Racer game board.

More details on Eduardo Cruz’ Arcade Hacker blog.

Check out the video after the break.

Continue reading “Deconstructing Sega’s System 16 security – part 2”

App note: PoE Powered Device (PD) rectifier bridge circuits

App note from ON Semiconductors regarding different bridge rectifier topologies and how to reduce power losses in these stages. Link here (PDF)

Power over Ethernet (PoE) is a technology which allows power sourcing equipment (PSE) to safely transfer power to a powered device (PD) through an Ethernet cable.

The majority of the power transferred to the PD normally goes to a DC−DC converter to supply loads such as a camera or an IP phone. However, not all the power delivered at the PSE output will be available to this load, due to a number of reasons. First of all, power loss occurs due to the resistance of the Ethernet cable. Additionally, the combined efficiency of the PD’s bridge rectifier and DC−DC converter is typically around 90%. It is important to keep in mind that the power is limited in a PoE system. When designing a powered device, reducing the power loss in the rectification and conversion stage means more power is available to the loads.

App note: Stepper motor module solution kit for LV8702V motor driver

Easily develop a motor conptrol application using this kit from ON Semiconductors without special knowledge of motor driver specs. Link here (PDF)

This kit provides an API function library for motor driver control designed to control the ON Semiconductor motor driver product (LV8702V) via the Arduino Micro microcomputer. It also provides a dedicated GUI for controlling motors connected to the Arduino Micro microcomputer that embedded with the API library from a computer via USB communication. This means that it is possible to easily tune and otherwise debug motor control sequences and operation parameters without developing motor control software for the Arduino Micro.

UHF version of TinySA

DuWayne KV4QB posted his UHF version of TinySA project:

I had started on the TinySA from Groups.io HBTE, but am still waiting on some parts that I had orderd than have yet to show up. Looking around I found a UHF version that covers 240 to 940 MHz. This only uses a single si4432 transceiver module, which I have on hand. So I will try to do a similar UHF version of the TinySA. Since this does not need the input LPF, mixer, and a high local oscillator, it should turn out to be a small instrument.

See the full post on DuWayne’s Place blog.

A circuit board from the Saturn V rocket, reverse-engineered and explained

Ken Shirriff writes, “In the Apollo Moon missions, the Saturn V rocket was guided by an advanced onboard computer system built by IBM. This system was built from hybrid modules, similar to integrated circuits but containing individual components. I reverse-engineered a circuit board from this system and determined its function: Inside the computer’s I/O unit, the board selected different data sources for the computer.
This post explains how the board worked, from the tiny silicon dies inside its hybrid modules to the board’s circuitry and its wiring in the rocket. This board was first studied by Fran Blanch in The Apollo Saturn V LVDC Project. Then EEVblog made a video about it. Now it’s my turn to analyze the board.”

More details on Ken Shirriff’s blog.