Archive for the ‘Electronics’ Category.
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 usually useful to first identify whether the issue at hand is related to hardware or software. Continue reading ‘Troubleshooting USB Circuit’ »
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 thought about using the same design with eight 74HC595s at first. But it seemed that the soldering would be a lot more challenging on the prototype board as there will be 8 chips and 64 resistors to solder. Continue reading ‘An 8-Digit 7 Segment 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 up with the following requirements: Continue reading ‘Building a Robotic Platform’ »
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. Continue reading ‘Yet Another Flyback Transformer Project’ »
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 further, I realized I could save some effort by just reusing what was already in place for the movement controls. Continue reading ‘Multiplexing the Drive 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 altogether. At first, I thought that I might have gotten a defective unit. But I quickly realized that it was a power issue — The USB port was not able to provide sufficient power to both my mouse and my keyboard. Continue reading ‘Simple External Powered USB Port’ »
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 a new oscilloscope for quite a while. This time around though, I wanted to get a digital storage oscilloscope (DSO) since in many cases, it is a lot more convenient to use. After reading about some rave reviews on Dave Jone’s EEVBlog about this Rigol DS1052E scope, it became apparent that this would be the ideal scope for my workshop. So without much hesitation, I ordered one. Continue reading ‘My New DS1052E Oscilloscope’ »
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. Continue reading ‘A Parallel Port Stepper Motor Driver With Discrete Components’ »
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 article on how to achieve this using a bipolar transistor (BJT). Here I will show you a similar relay control circuit built using an opto-isolator and a MOSFET. Continue reading ‘An Isolated MOSFET Serial Port Relay Controller’ »
One of my older CRT TVs does not have a built-in degauss button and after sitting in the corner of the basement for a couple of years, it somehow got magnetized pretty badly. The top two-thirds became totally disclorored with the “rainbow” effect. Continue reading ‘Building a Degaussing Coil’ »
A touch sensitive on/off switch can be made with a single MOSFET. The following schematics illustrate such a switch using only a power MOSFET (IRFZ22). Continue reading ‘The Simplest MOSFET On/Off Switch’ »
Many of you may still remember the capacitor plague that caused massive motherboard failures back in the early 2000s. While the practice of using cheap and unreliable electrolytic capacitors in computer components has largely died down nowadays, it seems that the issue has cropped up elsewhere. Continue reading ‘CFL Capacitor Problem’ »