Dilshan R Jayakody’s Web Log

When comes to electronic designing and testing, adjustable current sources facilitates to simulate "load" on the circuit(s). The most common use of "constant current source" is to test the performance of power supply units and battery packs. The current source introduced in this article is capable to handle current up to 6A with a maximum input voltage of 50V. This is an operational amplifier based adjustable current source and it uses LM358 in a general voltage follower configuration. To handle large currents we use four 0.1Ω 20W resistors as "load resistor", and those load resistors are drive through pair of 55N06 N-channel MOSFET transistors. Final view of adjustable constant current source prototype. The power supply unit of this project is built around 9V × 2 (2A) step-down transformer and it is designed to get regulated 12V DC voltage. In our design, this 12V power source is used to drive LM358 Op-Amp and 12V cooling fan. In our PCB desig...

This is a quick post to showcase 100W 4 channel AF dummy load which we build to test the output stages of audio power amplifiers. This dummy load use 4, 8Ω 100W wire wound resistors which are available on eBay . In this unit, all 4 resistors are mounted on 170mm × 40mm × 60mm high gauge aluminum heat sink. A prototype version of the 100W AF dummy load. It costs LKR1200 to build this unit and the most expensive component in this unit are wire wound resistors. At the time of writing these 100W resistor packs are available on eBay for USD $6.00.

This is a quick post about 100W RF dummy load which we build to use with HF and VHF transmitters and transceivers. This dummy load uses two non-inductive 100Ω 50W thick film power resistors manufactured by Vishay Sfernice and both these resisters are connected in parallel to achieve 50Ω impedance. The final version of 100W RF dummy load. Outer-casing (which also act as a heatsink) of dummy load is constructed using four bonded fin 50mm × 115mm × 20mm heatsinks. During our testing, we got flat 1:1.2 SWR with this dummy load. Internal view of 100W RF dummy load. Above mentioned 100Ω 50W power resistors are obtained through Farnell element14 .