The old axiom "you get what you pay for" is often invoked in discussions of product quality. It can also inspire curiosity as to what exactly one does get when the price paid for a product is significantly less than asked by others having comparable basic specifications. It was this spirit of curiosity that led a colleague to purchase a bench-type adjustable power supply, advertising a 0-15V, 0-2A output from a low-cost supplier for all of $17 USD. What exactly does that buy a person? Let's f...
The old axiom "you get what you pay for" is often invoked in discussions of product quality. It can also inspire curiosity as to what exactly one does get when the price paid for a product is significantly less than asked by others having comparable basic specifications. It was this spirit of curiosity that led a colleague to purchase a bench-type adjustable power supply, advertising a 0-15V, 0-2A output from a low-cost supplier for all of $17 USD. What exactly does that buy a person? Let's find out. Figure 1. Front panel view of the power supply to be examined. The model in question is branded Best, part number PS-1502DD. It's a single-output adjustable supply, with an adjustable current limit, a number of fixed voltage output settings, and one variable-output setting, in which the fine and coarse voltage adjustment outputs become active. Being a bench-type DC supply there are of course positive and negative output binding posts/banana-style terminals, as well as a third marked GND the likes of which are commonly found also in higher-cost supplies, and which typically provides a connection to the chassis/protective earth connection of a device. There's also a pair of 3-digit, 7-segment LED displays to indicate output voltage and current. And a power button. All are rather common features, which will be examined more closely in a bit. Edit: After completing this write-up, it was found that this same supply is available under maybe a half dozen different brand names, at price points ranging from the $17 USD range mentioned to upwards of $50 USD. Numerous resources are available demonstrating the basic functionality of the device; this article focuses more on reasons that a person might want to consider spending more on a device of this type. Figure 2. Rear panel of supply under examination. Scrutiny of the device's rear panel leads to a few amusing observations. The shiny holographic sticker with the company logo stands out. At one point in time such devices…