Dilshan R Jayakody’s Web Log

In my workshop, I got a couple of INGCO power tools. INGCO is a Chinese power tool manufacturer, and this brand is quite popular in Sri Lanka. Out of those tools I frequently used INGCO MG1502.2 mini drill. I purchased this drill three years back and mainly use for engraving and for precision drilling. A few days ago while I'm using this drill, it suddenly stopped. As a first thing, I checked brushes and mains-lead. After a few minutes of inspections, I found out that both brushes and mains lead are in perfect order. To further examine I decided to open the drill. The internal layout of this drill is quite simple. It mainly consists of an AC motor and electronic speed controller circuit. After a few checkups, I determined that the electronic speed controller is dead. In speed controller board I notice some unknown microcontroller, 74HC595 shift register, and Z0409MF TRIAC. As like many Chinese products here also they erased the IC number and other markings of the MCU. After ...

Analog AC line monitoring box This is a quick post about our newly constructed AC line monitoring unit. This unit consists with analog AC voltmeter, frequency meter and ammeter. Both voltmeter and frequency meter are 2.5 × 2.5 inch in size and ammeter is 3.5 × 3.5 inch in size. All these panel meters are commonly available in market. Ammeter in this assembly is connected to the mains line through 60A – 5A current transformer and all the other panel meters are coupled to the mains line through 100mA quick blow fuses. Wiring diagram of this unit is illustrated in below. Wiring diagram of analog AC line monitoring box Enclosure of this assembly is made with medium density plywood sheets. All the internal mains line of this unit is wired using 2 × 12 SWG copper wires. We construct this unit to monitor the AC line status continuously and also to get some line measurements accurately (from known reference level). In our version of line monitor all the AC line connectors c...

This a quick post regarding homemade 300V - 2.3A isolation transformer. This transformer is a part of my ongoing 300V AC/DC variable power supply project and it’s boxed as a separate unit because of its heavy weight and size. 700VA isolation transformer with enclosure All the parameters of this transformer are calculated using small Python script which I was written sometimes ago. This script support for step-up, step-down or 1:1 power transformer windings and it can execute on any platform where Python 2.7 (or newer version) is supported. In isolation transformers separation between primary and secondary windings is an important factor. In this transformer I use multiple layers of 3M Scotch Electrical Insulation tape as primary and secondary winding separator. Standard 50mm PVC electrical insulation tape is used to cover secondary winding of this transformer. Improper connections or construction of this transformer may leads to fire or lethal electrical shock. Because of...