The drive circuits for Unipolar stepper motors are usually very simple. In its simplest form, a transistor or MOSFET is used to drive each section of the windings. With this design, the control signal must be supplied programmatically to the…
Just because you are using a true RMS multimeter does not automatically mean you should always trust the readings of your measurements. In fact, most true RMS multimeters can only offer reliable readings under certain conditions. In this post, I…
Most of the multimeters do not offer resistance measurement in the milliohm range. In most meters a typically Ohm range has an accuracy of 0.1 ohm and is too coarse for measuring small resistance. Of course, some of the high-end…
One of my computers has been unstable for quite some time now. It had been crashing and freezing up once a while in the past, but it has become noticeably worse in recent months and sometimes the computer would crash…
One of my RSA SecureID tokens had recently expired, so I decided to do a teardown to see what is inside. While there was one such teardowns posted on EETimes a few years ago, I thought it would still be…
The other day, I needed to measure the AC current of my water heater without having to disconnect the wiring. Typically, you would need a clamp meter to do this. Since I don’t have a clamp meter, I thought I…
I have built some circuits that interface with computer USB ports. On several occasions, I had built the circuits but for whatever reason they did not seem to work. Since most USB firmware is rather complex in nature, it is…
I built a 4-digit 7 segment display last year. In that design, I used four 74HC595 shift registers to drive the four individual 7 segment displays, with one for each digit. So when I wanted to build an 8-digit display,…
I started this project a while ago. My intention was to adapt a toy remote controlled vehicle into a generic robotic platform, which would enable me to do some experiments with robotics. To make the platform more generic, I came…
I was looking for some parts a couple of weeks ago and came across an old TV flyback transfomer, so I thought I would build a project with it.
I am in the process of converting a remote controlled toy vehicle to an autonomous robotic platform. My initial thought was to just get rid of the existing circuit and add on my own. But after analyzing the control circuit…
I recently bought a TrendNet TK-207K KVM switch. After hooking up my mouse and keyboard, I was suprised to find out that the setting did not work. The mouse and keyboard would act strangely and sometimes one would stop working…
I used to own an all-transistor, single channel 10 MHz analog oscilloscope. While it was not adequate by nowadays standard, it served me quite well for many years. The scope was later sold and I had been thinking about getting…
Using PC’s parallel port is a convenient way to control a stepper motor. For unipolar stepper motors, up to two motors can be controlled with the 8bit data line.
Using DTR (data terminal ready) and RTS (request to send) pins of a PC serial port (RS-232) without actually using the serial data pins, we can interface at least two relay devices with a computer. Windmeadow Labs has an excellent…