PWR-1 Power Protection and Filter

	Click on “thumbnails” to enlarge

Most of us have been there. For whatever reason, and in fact contrary to all reason, you’ve reversed the polarity of your power connection and now one, some, or maybe all of the active devices in your homebrew rig–transistors mostly (including those built into ICs)–are toast.

All of us have been somewhere else, too: the “undiscovered country” of noise conducted through our power supplies. Because it’s very uncommon to shield the power cables we connect to our rigs, a lot of noise is also picked up in them, fed into our power inputs, and then bounces around inside our sensitive circuitry. What’s more, we often generate noise inside our gear, commonly from digital devices such as Arduinos, displays, rotary encoders, and the like. In short, we’re happier when we can either eliminate or reduce noise sources–certainly those over which we have some control.

This is where the PWR-1 comes in. Its P-Channel MOSFET instantly shuts off power if polarity has been reversed, and its low-pass and common-mode filtering keep noise down to a tolerable level. Some circuits–such as a direct-conversion receivers–are susceptible to common-mode AC hum. The PWR-1 suppresses that to inaudible levels.

The PWR-1 is available in two versions: one with just the fuse and reverse-polarity protection, and one to also include noise filtering. Each is available only as a kit.

By the way, if you want to monitor the voltage and current passing through the PWR-1, check out Adafruit’s INA238 DC Current Voltage Power Monitor. It measures both voltage (to 85VDC) and current (to 10A) and it has 16 or 20-bit accuracy readable via I2C.

PWR-1 Schematic