App note: Minimizing the temperature dependence of digital potentiometers

an_nidec_copal_an9

Application notes from NIDEC COPAL Electronics Corp. about digital potentiometer’s temperature dependence. Link here (PDF)

The digital potentiometers (DP) has two temperature dependent parameters, the TC of the end-to-end resistance Rpot and the ratiometric TC. The temperature dependence of the parameters of an analog circuit using a digital potentiometers is reduced if the performance of the circuit is shifted from the TC of the end-to-end resistance of the pot to the ratiometric TC.

from Dangerous Prototypes http://ift.tt/2vigGv7

App note: Potentiometers and trimmers

an_vishay_pot_trim

App note from Vishay on variable resistors primer. Link here (PDF)

A potentiometer is a mechanically actuated variable resistor with three terminals. Two of the terminals are linked to the ends of the resistive element and the third is connected to a mobile contact moving over the resistive track. The output voltage becomes a function of the position of this contact. Potentiometer is advised to be used as a voltage divider.

from Dangerous Prototypes http://ift.tt/2xDwZPV

Examining a vintage RAM chip, I find a counterfeit with an entirely different die inside

picture-die-structures

Ken Shirriff writes, “A die photo of a vintage 64-bit TTL RAM chip came up on Twitter recently, but the more I examined the photo the more puzzled I became. The chip didn’t look at all like a RAM chip or even a TTL chip, and in fact appeared partially analog. By studying the chip’s circuitry closely, I discovered that this RAM chip was counterfeit and had an entirely different die inside. In this article, I explain how I analyzed the die photos and figured out what it really was.”

See the full post on his blog.

from Dangerous Prototypes http://ift.tt/2wbs5Kx

Free PCB coupon via Facebook to 2 random commenters

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:

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • We’ll contact you via Facebook 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.

from Dangerous Prototypes http://ift.tt/2vdtXoB

Solid-state joystick

pics-IMG_20170818_165822-600

Paul Gardner-Stephen writes:

Early in the year, one of my colleagues, Damian, showed me one of these strain-gauge solid-state joysticks that they were using as part of the undergraduate engineering curriculum.
Their goal was to teach the students how to read strain-gauges. But I immediately saw the applicability for making a no-moving-parts super-robust joystick for the MEGA65 and all other retro computer users.

See the full post on his blog.

from Dangerous Prototypes http://ift.tt/2vccSYs

Microcontroller action potential generator

pics-ap-generator-running-600

Scott Harden writes:

Here I demonstrate how to use a single microcontroller pin to generate action-potential-like waveforms. The output is similar my fully analog action potential generator circuit, but the waveform here is created in an entirely different way. A microcontroller is at the core of this project and determines when to fire action potentials. Taking advantage of the pseudo-random number generator (rand() in AVR-GCC’s stdlib.h), I am able to easily produce unevenly-spaced action potentials which more accurately reflect those observed in nature. This circuit has a potentiometer to adjust the action potential frequency (probability) and another to adjust the amount of overshoot (afterhyperpolarization, AHP). I created this project because I wanted to practice designing various types of action potential measurement circuits, so creating an action potential generating circuit was an obvious perquisite.

See the full post at SWHarden.com.

Check out the video after the break.

from Dangerous Prototypes http://ift.tt/2wx0u8N

Free PCB Sunday: Pick your PCB

BP-600x373

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:

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • Be sure to use a real e-mail in the address field so we can contact you with the coupon.
  • Limit one PCB per address per month please.
  • Like everything else on this site, PCBs are offered without warranty.
  • PCBs are scrap and have no value, due to limited supply it is not possible to replace a board lost in the post

Be the first to comment, subscribe to the RSS feed.

from Dangerous Prototypes http://ift.tt/2uWKAF1

App note: How RF transformers work and how they are measured

an_minicircuits_AN20-001

Application note from Mini-Circuits about transformers, this time the RF transformers. Link here (PDF)

RF transformers are widely used in electronic circuits for
* Impedance matching to achieve maximum power transfer and to suppress undesired signal reflection.
* Voltage, current step-up or step-down.
* DC isolation between circuits while affording efficient AC transmission.
* Interfacing between balanced and unbalanced circuits; example: balanced amplifiers.

from Dangerous Prototypes http://ift.tt/2wm9vSC

App note: Transformers

an_minicircuits_AN20-002

App note from Mini-Circuits on transformer types and some basics of them. Link here (PDF)

The purpose of this application note is to describe the fundamentals of RF and microwave transformers and to provide guidelines to users in selecting proper transformer to suit their applications. It is limited to core-and-wire and LTCC transformers.

 

from Dangerous Prototypes http://ift.tt/2fWu3KJ

App note: USB hardware design guide

1apps

An app note from Silicon Labs with design guidelines for implementing USB host and device applications using USB capable EFM32 microcontrollers. Link here. (PDF!)

This document will explain how to connect the USB pins of an EFM32 microcontroller, and will give general guidelines on PCB design for USB applications. First some quick rules-of-thumb for routing and layout are presented before a more detailed explanation follows.
The information in this document is meant to supplement the information already presented in Energy Micro application notes AN0002 Hardware Design Considerations and AN0016 Oscillator Design Considerations, and it is recommended to follow these guidelines as well.

from Dangerous Prototypes http://ift.tt/2wd2005