WebScale

Measure weight using a Stamps.com digital USB postage scale.

Hardware

I successfully performed these steps in September 2014. Today, it may work differently, or not at all.

1. Sign up for free trial at Stamps.com.
2. During signup, request a complimentary 5-pound digital postage scale. Pay $9.99 USD shipping and handling.
3. Before the four-week trial is up, cancel your account and avoid the monthly fee.

Installation

This package is available on npm.

$ npm install webscale

In the event of installation trouble, refer to the node-hid documentation.

Usage

const WebScale = require('webscale');
const webScale = new WebScale();

webScale.on('change:weight', ounces => {
    console.log(`${ounces} oz.`);
});

See also test-client.js.

Events

change:weight

Called whenever the scale's weight reading changes.

Arguments

• ounces how much weight is on the scale, in ounces. Floating-point number with precision of one digit after the decimal place (tenths of ounces). Can be negative if the scale was tared with weight on it.

connected

Called when the program first starts and connects successfully to the device, or when it reconnects after losing the connection.

disconnected

Called when the device is unplugged or powered off, and once per reconnect attempt.

error

An error with the USB device occurred (except disconnections, see above).

Arguments

• error The error from node-hid.

Methods

tare()

Reset the scale so the current weight will be read as zero. The scale will also automatically tare itself each time it powers on.

disconnect()

Disconnect from the USB device.

See Also

• Aldaviva/WebScale.net - this library ported from Node.js to .NET