Voltage divider calculator

voltage_divider.js

/**
 * @typedef {{
 * 	vin: number,
 *  vout: number
 * } & ({r1: number} | {r2: number})} TVoltageDividerParams
 * 
 * @typedef {{
 * 	vin: number,
 * 	vout: number,
 * 	r: Set<number> | number[]
 * }} TVoltageDividerAvailableParams
 * 
 * @typedef {{
 * 	r1: number, r2: number, delta: number
 * }} TVoltageDividerAvailableResult
 */

/**
 * Returns r2 or r1 given the other 3 parameters
 * @param {TVoltageDividerParams} param0 
 * @returns {number | NaN}
 */
function voltage_divider({ vin, vout, r1, r2 }) {
	if (typeof r1 == "number") {
		return (vout * r1) / (vin - vout);
	}
	else if (typeof r2 == "number") {
		return ((vin * r2) / vout) - r2;
	}
	else {
		return NaN;
	}
}

/**
 * Selects the best combination given the available resistances
 * @param {TVoltageDividerAvailableParams} param0
 * @returns {TVoltageDividerAvailableResult} 
 */
function voltage_divider_available({ vin, vout, r }) {
	const resistance_set = new Set(r);

	/** @type {TVoltageDividerAvailableResult} */
	let closest = { r1: 0, r2: 0, delta: Infinity };

	// r^2
	for (const resistance of resistance_set) {
		const r2_desired = voltage_divider({ r1: resistance, vin, vout });
		for (const r2_candidate of resistance_set) {
			const delta = Math.abs(r2_candidate - r2_desired);

			if (delta < closest.delta)
				closest = { r1: resistance, r2: r2_candidate, delta };
		}
	}

	return closest;
}