Arduino Library For LTC4151

LTC4151 is a high voltage I2C current and voltage monitor. It is capable of monitoring input voltage ranging from 7V to 80V with the onboard 12-bit ADC. It can also measure the high side current and an additional external voltage with the same 12-bit ADC resolution. Besides LTC4151, LTC4151-1 and LTC4151-2 have split SDA (SDAO and SDAI) for interfacing with Opto-Isolators.
Read more…

HP 436A Power Meter Teardown

HP 436A is a power meter capable of measuring RF power between -70 dBm and 44 dBm (roughly between 0.1 nW to 25 W) with a frequency range from 100 kHz all the way upwards to 110 GHz depending on the sensor module selected. This power meter was made in the early 70′s and has long been discontinued.
Read more…

A Digital Thermometer Hygrometer With Analog Displays

It seems that you can’t visit to a microcontroller website without seeing a digital thermometer/hygrometer build of some kind. After all, it is pretty easy to build and at the same time quite useful as well. In this post, I will show you yet another thermometer/hygrometer build. But instead of using an LCD or 7 segment display for the output, I decided to go retro, using two “needles” to display the temperature and humidity readings instead.
Read more…

BJT In Reverse Avalanche Mode

Transistors operating in their avalanche regions are often used to generate fast rise pulses (see avalanche pulse generator using 2N3904). Many transistors can also avalanche when the connections to collector and emitter are reversed. When operating in reverse avalanche region, these transistors are sometimes referred to as negistors.
Read more…

Extending DAC Resolution Using Digital Potentiometer

One way to extend the resolution of a digital-to-analog converter (DAC) is by employing a sigma-delta converter in software. The main disadvantage of such approach is the slow speed. Alternatively, we can use some extra hardware to extend the usable resolution of a DAC. In this post, I will illustrate one such method to extend an 8-bit DAC to 16 bits using a digital potentiometer.
Read more…

Testing of Two Three-Phase BLDC Motor Drivers

I was doing a project that needed a driver for hard disk spindle motors. While I could use a microcontroller to generate the required driving waveform sequence, keeping the waveform in sync with the motor rotation is actually quite tricky especially at higher rotation speeds. To ensure the correct timing sequence, a back-EMF controller is required for these sensorless three-phase BLDC motors.
Read more…

HP 6113A Teardown And Calibration

A couple of weeks ago I did a teardown of HP 6181C — a precision DC current source made in the late 70′s and early 80′s. This time around, I am going to show some pictures of an HP 6113A precision DC power supply and do a basic calibration using my Keithley 196 multimeter.
Read more…

Arduino Libraries Uploaded to GitHub

Over the years I have created quite a few libraries for Arduino. I finally uploaded them to GitHub a couple of days ago so that they are now all at one place and are easier to find.
Read more…

HP 6181C DC Current Source Teardown

HP 6181C is a lab grade 0 to 250 mA current source manufactured back in the late 70′s and early 80′s. There does not seem to be any pictures on the Internet for this particular model so I thought I would do a teardown here.
Read more…

Simple hFE Adapter For Cheap DMMs

Getting a rough measurement of the transistor hFE’s is useful when designing analog circuits. Unfortunately, only the lower end DMMs nowadays offer such functionality as it is becoming less and less useful to measure transistor hFEs in a world that is dominated by digital circuitry. Also hFE varies in different biasing situations and the hFE measurements on these cheap DMMs are typically done with a fixed base current (approximately 10 µA) in DC mode. But even with these limitations, hFE measurements can still be quite useful.
Read more…

LM92 Library for Arduino

LM92 is a 12-bit + sign temperature sensor from Texas Instruments. This sensor operates on the I2C interface and can achieve an accuracy as high as ± 0.33 °C within the typical temperature measurement range. I created a comprehensive Arduino library for this sensor (the library can be downloaded towards the end) and in this post I will explain each of the functions in detail.
Read more…

A Simple Serial Protocol

We can send and receive commands wirelessly with Arduino by using these cheap RF data link transmitters/receivers. I like these RF modules because they can be hooked up to pretty much any device that supports serial communications (e.g. devices equipped with either hardware or software UART).
Read more…

Peltier Cooler Module Repair

I bought a couple of Peltier cooler modules on eBay a while ago for some experiments. Of course, as I expected the quality of those cheap modules were pretty poor. After a couple of hours of continuous operation, both modules failed. So I decided to take a look to see if they could be repaired.
Read more…

A Digitally Controlled Dual Tracking Power Supply — III

In part 1 of this series of blog postings, I showed my preliminary design of a dual tracking linear power supply. In part 2, I showed the completed design and also the finished power supply circuits. And as promised last time, I have made a couple of videos showing the measurements of a few key parameters and will share the results here.
Read more…

A Digitally Controlled Dual Tracking Power Supply — II

In my previous post, I showed my design of a dual tracking ±30V linear power supply. My goal was to use the transformer (28V+28V, center tapped) from an old Deltron W127G open-frame power supply and build a lab supply that can be digitally adjusted in both constant voltage and constant current modes. I also wanted each of the channels to be able to deliver up to 10 Amps of current so that I could fully utilize the 540VA transfomer from the W127G.
Read more…